| Message ID | 20220118131216.85338-1-jefflexu@linux.alibaba.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | fscache,erofs: fscache-based demand-read semantics | expand |
Hi David, On Tue, Jan 18, 2022 at 09:11:56PM +0800, Jeffle Xu wrote: > changes since v1: > - rebase to v5.17 > - erofs: In chunk based layout, since the logical file offset has the > same remainder over PAGE_SIZE with the corresponding physical address > inside the data blob file, the file page cache can be directly > transferred to netfs library to contain the data from data blob file. > (patch 15) (Gao Xiang) > - netfs,cachefiles: manage logical/physical offset separately. (patch 2) > (It is used by erofs_begin_cache_operation() in patch 15.) > - cachefiles: introduce a new devnode specificaly for on-demand reading. > (patch 6) > - netfs,fscache,cachefiles: add new CONFIG_* for on-demand reading. > (patch 3/5) > - You could start a quick test by > https://github.com/lostjeffle/demand-read-cachefilesd > - add more background information (mainly introduction to nydus) in the > "Background" part of this cover letter > > [Important Issues] > The following issues still need further discussion. Thanks for your time > and patience. > > 1. I noticed that there's refactoring of netfs library[1], and patch 1 > is not needed since [2]. > > 2. The current implementation will severely conflict with the > refactoring of netfs library[1][2]. The assumption of 'struct > netfs_i_context' [2] is that, every file in the upper netfs will > correspond to only one backing file. While in our scenario, one file in > erofs can correspond to multiple backing files. That is, the content of > one file can be divided into multiple chunks, and are distrubuted over > multiple blob files, i.e. multiple backing files. Currently I have no > good idea solving this conflic. > Would you mind give more hints on this? Personally, I still think fscache is useful and clean way for image distribution on-demand load use cases in addition to cache network fs data as a more generic in-kernel caching framework. From the point view of current codestat, it has slight modification of netfslib and cachefiles (except for a new daemon): fs/netfs/Kconfig | 8 + fs/netfs/read_helper.c | 65 ++++++-- include/linux/netfs.h | 10 ++ fs/cachefiles/Kconfig | 8 + fs/cachefiles/daemon.c | 147 ++++++++++++++++- fs/cachefiles/internal.h | 23 +++ fs/cachefiles/io.c | 82 +++++++++- fs/cachefiles/main.c | 27 ++++ fs/cachefiles/namei.c | 60 ++++++- Besides, I think that cookies can be set according to data mapping (instead of fixed per file) will benefit the following scenario in addition to our on-demand load use cases: It will benefit file cache data deduplication. What I can see is that netfslib may have some follow-on development in order to support encryption and compression. However, I think cache data deduplication is also potentially useful to minimize cache storage since many local fses already support reflink. However, I'm not sure if it's a great idea that cachefile relies on underlayfs abilities for cache deduplication. So for cache deduplication scenarios, I'm not sure per-file cookie is still a good idea for us (or alternatively, maintain more complicated mapping per cookie inside fscache besides filesystem mapping, too unnecessary IMO). By the way, in general, I'm not sure if it's a great idea to cache in per-file basis (especially for too many small files), that is why we introduced data deduplicated blobs. At least, it's simpler for read-only fses. Recently, I found another good article to summarize this: http://0pointer.net/blog/casync-a-tool-for-distributing-file-system-images.html Thanks, Gao Xiang
Hi David, Sincerely would you mind sharing if you like this patch set or not? It seems that the use case of file-based on-demand load is quite general. And as Gao Xaing noted, we still prefer fscache to implement this scenario, whilst fscache has well worked as the local cache for remote netfs. Humbly I'd like to know if this potential new requirement for fscache meets your expectation or future plan for fscache. If it is, then we can improve the patch set in the later versions. Besides let me know if it indeed deviates from the roadmap of fscache. Thanks, Jeffle On 1/19/22 2:40 PM, Gao Xiang wrote: > Hi David, > > On Tue, Jan 18, 2022 at 09:11:56PM +0800, Jeffle Xu wrote: >> changes since v1: >> - rebase to v5.17 >> - erofs: In chunk based layout, since the logical file offset has the >> same remainder over PAGE_SIZE with the corresponding physical address >> inside the data blob file, the file page cache can be directly >> transferred to netfs library to contain the data from data blob file. >> (patch 15) (Gao Xiang) >> - netfs,cachefiles: manage logical/physical offset separately. (patch 2) >> (It is used by erofs_begin_cache_operation() in patch 15.) >> - cachefiles: introduce a new devnode specificaly for on-demand reading. >> (patch 6) >> - netfs,fscache,cachefiles: add new CONFIG_* for on-demand reading. >> (patch 3/5) >> - You could start a quick test by >> https://github.com/lostjeffle/demand-read-cachefilesd >> - add more background information (mainly introduction to nydus) in the >> "Background" part of this cover letter >> >> [Important Issues] >> The following issues still need further discussion. Thanks for your time >> and patience. >> >> 1. I noticed that there's refactoring of netfs library[1], and patch 1 >> is not needed since [2]. >> >> 2. The current implementation will severely conflict with the >> refactoring of netfs library[1][2]. The assumption of 'struct >> netfs_i_context' [2] is that, every file in the upper netfs will >> correspond to only one backing file. While in our scenario, one file in >> erofs can correspond to multiple backing files. That is, the content of >> one file can be divided into multiple chunks, and are distrubuted over >> multiple blob files, i.e. multiple backing files. Currently I have no >> good idea solving this conflic. >> > > Would you mind give more hints on this? Personally, I still think fscache > is useful and clean way for image distribution on-demand load use cases > in addition to cache network fs data as a more generic in-kernel caching > framework. From the point view of current codestat, it has slight > modification of netfslib and cachefiles (except for a new daemon): > fs/netfs/Kconfig | 8 + > fs/netfs/read_helper.c | 65 ++++++-- > include/linux/netfs.h | 10 ++ > > fs/cachefiles/Kconfig | 8 + > fs/cachefiles/daemon.c | 147 ++++++++++++++++- > fs/cachefiles/internal.h | 23 +++ > fs/cachefiles/io.c | 82 +++++++++- > fs/cachefiles/main.c | 27 ++++ > fs/cachefiles/namei.c | 60 ++++++- > > Besides, I think that cookies can be set according to data mapping > (instead of fixed per file) will benefit the following scenario in > addition to our on-demand load use cases: > It will benefit file cache data deduplication. What I can see is that > netfslib may have some follow-on development in order to support > encryption and compression. However, I think cache data deduplication > is also potentially useful to minimize cache storage since many local > fses already support reflink. However, I'm not sure if it's a great > idea that cachefile relies on underlayfs abilities for cache deduplication. > So for cache deduplication scenarios, I'm not sure per-file cookie is > still a good idea for us (or alternatively, maintain more complicated > mapping per cookie inside fscache besides filesystem mapping, too > unnecessary IMO). > > By the way, in general, I'm not sure if it's a great idea to cache in > per-file basis (especially for too many small files), that is why we > introduced data deduplicated blobs. At least, it's simpler for read-only > fses. Recently, I found another good article to summarize this: > http://0pointer.net/blog/casync-a-tool-for-distributing-file-system-images.html > > Thanks, > Gao Xiang >
Jeffle Xu <jefflexu@linux.alibaba.com> wrote: > You could start a quick test by > https://github.com/lostjeffle/demand-read-cachefilesd Can you pull this up to v5.17-rc1 or my netfs-lib branch? https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=netfs-lib I'll do my best to have a look at it tomorrow. Thanks, David
On 1/25/22 1:23 AM, David Howells wrote: > Jeffle Xu <jefflexu@linux.alibaba.com> wrote: > >> You could start a quick test by >> https://github.com/lostjeffle/demand-read-cachefilesd There is a quick test script in this repo in addition to the daemon (temporarily named with cachefilesd2). > > Can you pull this up to v5.17-rc1 or my netfs-lib branch? > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=netfs-lib While this kernel patch set is basically rebased to v5.17-rc1, rather than netfs-lib branch. I can see there's quite many refactoring for netfs lib in netfs-lib branch. > > I'll do my best to have a look at it tomorrow. > Thanks a lot.
On 1/25/22 1:23 AM, David Howells wrote: > Jeffle Xu <jefflexu@linux.alibaba.com> wrote: > >> You could start a quick test by >> https://github.com/lostjeffle/demand-read-cachefilesd > > Can you pull this up to v5.17-rc1 or my netfs-lib branch? > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=netfs-lib > Hi, you can check this kernel patch set on the following branch, which has been rebased to v5.17-rc1. https://github.com/lostjeffle/linux/commits/master
Jeffle Xu <jefflexu@linux.alibaba.com> wrote: > The following issues still need further discussion. Thanks for your time > and patience. > > 1. I noticed that there's refactoring of netfs library[1], > ... > [1] https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=netfs-lib Yes. I'm working towards getting netfslib to do handling writes and dio as well as reads, along with content crypto/compression, and the idea I'm aiming towards is that you just point your address_space_ops at netfs directly if possible - but it's going to require its own context now to manage pending writes. See my netfs-experimental branch for more of that - it's still a work in progress, though. Btw, you could set rreq->netfs_priv in ->init_rreq() rather than passing it in to netfs_readpage(). > 2. The current implementation will severely conflict with the > refactoring of netfs library[1][2]. The assumption of 'struct > netfs_i_context' [2] is that, every file in the upper netfs will > correspond to only one backing file. While in our scenario, one file in > erofs can correspond to multiple backing files. That is, the content of > one file can be divided into multiple chunks, and are distrubuted over > multiple blob files, i.e. multiple backing files. Currently I have no > good idea solving this conflic. I can think of a couple of options to explore: (1) Duplicate the cachefiles backend. You can discard a lot of it, since a much of it is concerned with managing local modifications - which you're not going to do since you have a R/O filesystem and you're looking at importing files into the cache externally to the kernel. I would suggest looking to see if you can do the blob mapping in the backend rather than passing the offset down. Maybe make the cookie index key hold the index too, e.g. "/path/to/file+offset". Btw, do you still need cachefilesd for its culling duties? (2) Do you actually need to go through netfslib? Might it be easier to call fscache_read() directly? Have a look at fs/nfs/fscache.c > Besides there are still two quetions: > - What's the plan of [1]? When is it planned to be merged? Hopefully next merge window, but that's going to depend on a number of things. > - It seems that all upper fs using fscache is going to use netfs API, > while the APIs like fscache_read_or_alloc_page() are deprecated. Is > that true? fscache_read_or_alloc_page() is gone completely. You don't have to use the netfs API. You can talk to fscache directly, doing DIO from the cache to an xarray-class iov_iter constructed from your inode's pagecache. netfslib provides/will provide a number of services, such as multipage folios, transparent caching, crypto, compression and hiding the existence of pages/folios from the filesystem as entirely as possible. However, you already have some of these implemented on top of iomap for the blockdev interface, it would appear. David
David Howells <dhowells@redhat.com> wrote: > (1) Duplicate the cachefiles backend. You can discard a lot of it, since a > much of it is concerned with managing local modifications - which you're > not going to do since you have a R/O filesystem and you're looking at > importing files into the cache externally to the kernel. Take the attached as a start. It's completely untested. I've stripped out anything to do with writing to the cache, making directories, etc. as that can probably be delegated to the on-demand creation. You could drive on-demand creation from the points where it would create files. I've put some "TODO" comments in there as markers. You could also strip out everything to do with invalidation and also make it just fail if it encounters a file type that it doesn't like or a file that is not correctly labelled for a coherency attribute. Also, since you aren't intending to write anything or create new files here, there's no need to do the space checking - so I've got rid of all that too. I've also made it open the backing files read only and got rid of the trimming to I/O blocksize for DIO purposes. The userspace side can take care of that - and, besides, you want to have multiple files within a backing file, right? You might want to stop it from marking cache *files* in use (but only mark directories). It doesn't matter so much as you aren't going to get coherency issues from having multiple writers to the same file. You then need to add a file offset member to the erofscache_object struct, set that when the backing file is looked up and add it to the file position in erofscache_read(). You also need to look at erofscache_prepare_read(). If your files are contiguous complete blobs, that can be a lot simpler. Also, you might want to rename erofscache to something more suitable. David --- commit 6fb0e557451e1cd909679fea183822ae92eed67f Author: David Howells <dhowells@redhat.com> Date: Tue Jan 25 16:44:10 2022 +0000 erofs: Create specialised cache backend diff --git a/fs/Kconfig b/fs/Kconfig index 7a2b11c0b803..4ed1e704c0d4 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -133,6 +133,7 @@ menu "Caches" source "fs/netfs/Kconfig" source "fs/fscache/Kconfig" source "fs/cachefiles/Kconfig" +source "fs/erofscache/Kconfig" endmenu diff --git a/fs/Makefile b/fs/Makefile index dab324aea08f..4780b9c919a8 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -128,6 +128,7 @@ obj-$(CONFIG_NILFS2_FS) += nilfs2/ obj-$(CONFIG_BEFS_FS) += befs/ obj-$(CONFIG_HOSTFS) += hostfs/ obj-$(CONFIG_CACHEFILES) += cachefiles/ +obj-$(CONFIG_EROFSCACHE) += erofscache/ obj-$(CONFIG_DEBUG_FS) += debugfs/ obj-$(CONFIG_TRACING) += tracefs/ obj-$(CONFIG_OCFS2_FS) += ocfs2/ diff --git a/fs/erofscache/Kconfig b/fs/erofscache/Kconfig new file mode 100644 index 000000000000..29503879dce4 --- /dev/null +++ b/fs/erofscache/Kconfig @@ -0,0 +1,28 @@ +# SPDX-License-Identifier: GPL-2.0-only + +config EROFSCACHE + tristate "Filesystem caching on files" + depends on FSCACHE && BLOCK + help + This permits use of a mounted filesystem as a cache for other + filesystems - primarily networking filesystems - thus allowing fast + local disk to enhance the speed of slower devices. + + See Documentation/filesystems/caching/erofscache.rst for more + information. + +config EROFSCACHE_DEBUG + bool "Debug Erofscache" + depends on EROFSCACHE + help + This permits debugging to be dynamically enabled in the filesystem + caching on files module. If this is set, the debugging output may be + enabled by setting bits in /sys/modules/erofscache/parameter/debug or + by including a debugging specifier in /etc/erofscached.conf. + +config EROFSCACHE_ERROR_INJECTION + bool "Provide error injection for erofscache" + depends on EROFSCACHE && SYSCTL + help + This permits error injection to be enabled in erofscache whilst a + cache is in service. diff --git a/fs/erofscache/Makefile b/fs/erofscache/Makefile new file mode 100644 index 000000000000..e22df4eb400b --- /dev/null +++ b/fs/erofscache/Makefile @@ -0,0 +1,20 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Makefile for on-demand caching for erofs +# + +erofscache-y := \ + cache.o \ + daemon.o \ + interface.o \ + io.o \ + key.o \ + main.o \ + namei.o \ + security.o \ + volume.o \ + xattr.o + +erofscache-$(CONFIG_EROFSCACHE_ERROR_INJECTION) += error_inject.o + +obj-$(CONFIG_EROFSCACHE) := erofscache.o diff --git a/fs/erofscache/cache.c b/fs/erofscache/cache.c new file mode 100644 index 000000000000..fad00abbc218 --- /dev/null +++ b/fs/erofscache/cache.c @@ -0,0 +1,199 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Manage high-level VFS aspects of a cache. + * + * Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/slab.h> +#include <linux/statfs.h> +#include <linux/namei.h> +#include "internal.h" + +/* + * Bring a cache online. + */ +int erofscache_add_cache(struct erofscache_cache *cache) +{ + struct fscache_cache *cache_cookie; + struct path path; + struct dentry *graveyard, *cachedir, *root; + const struct cred *saved_cred; + int ret; + + _enter(""); + + cache_cookie = fscache_acquire_cache(cache->tag); + if (IS_ERR(cache_cookie)) + return PTR_ERR(cache_cookie); + + /* we want to work under the module's security ID */ + ret = erofscache_get_security_ID(cache); + if (ret < 0) + goto error_getsec; + + erofscache_begin_secure(cache, &saved_cred); + + /* look up the directory at the root of the cache */ + ret = kern_path(cache->rootdirname, LOOKUP_DIRECTORY, &path); + if (ret < 0) + goto error_open_root; + + cache->mnt = path.mnt; + root = path.dentry; + + cache->bsize = EROFSCACHE_DIO_BLOCK_SIZE; + cache->bshift = ilog2(cache->bsize); + + ret = -EINVAL; + if (is_idmapped_mnt(path.mnt)) { + pr_warn("File cache on idmapped mounts not supported"); + goto error_unsupported; + } + + /* Check features of the backing filesystem: + * - Directories must support looking up + * - We use xattrs to store metadata + * - We use DIO to pages, so the blocksize mustn't be too big. + */ + ret = -EOPNOTSUPP; + if (d_is_negative(root) || + !d_backing_inode(root)->i_op->lookup || + !(d_backing_inode(root)->i_opflags & IOP_XATTR) || + root->d_sb->s_blocksize > PAGE_SIZE) + goto error_unsupported; + + /* determine the security of the on-disk cache as this governs + * security ID of files we create */ + ret = erofscache_determine_cache_security(cache, root, &saved_cred); + if (ret < 0) + goto error_unsupported; + + /* get the cache directory and check its type */ + cachedir = erofscache_get_directory(cache, root, "cache"); + if (IS_ERR(cachedir)) { + ret = PTR_ERR(cachedir); + goto error_unsupported; + } + + cache->store = cachedir; + + /* get the graveyard directory */ + graveyard = erofscache_get_directory(cache, root, "graveyard"); + if (IS_ERR(graveyard)) { + ret = PTR_ERR(graveyard); + goto error_unsupported; + } + + cache->graveyard = graveyard; + cache->cache = cache_cookie; + + ret = fscache_add_cache(cache_cookie, &erofscache_cache_ops, cache); + if (ret < 0) + goto error_add_cache; + + /* done */ + set_bit(EROFSCACHE_READY, &cache->flags); + dput(root); + + pr_info("File cache on %s registered\n", cache_cookie->name); + + erofscache_end_secure(cache, saved_cred); + _leave(" = 0 [%px]", cache->cache); + return 0; + +error_add_cache: + erofscache_put_directory(cache->graveyard); + cache->graveyard = NULL; +error_unsupported: + erofscache_put_directory(cache->store); + cache->store = NULL; + mntput(cache->mnt); + cache->mnt = NULL; + dput(root); +error_open_root: + erofscache_end_secure(cache, saved_cred); +error_getsec: + fscache_relinquish_cache(cache_cookie); + cache->cache = NULL; + pr_err("Failed to register: %d\n", ret); + return ret; +} + +/* + * Mark all the objects as being out of service and queue them all for cleanup. + */ +static void erofscache_withdraw_objects(struct erofscache_cache *cache) +{ + struct erofscache_object *object; + unsigned int count = 0; + + _enter(""); + + spin_lock(&cache->object_list_lock); + + while (!list_empty(&cache->object_list)) { + object = list_first_entry(&cache->object_list, + struct erofscache_object, cache_link); + erofscache_see_object(object, erofscache_obj_see_withdrawal); + list_del_init(&object->cache_link); + fscache_withdraw_cookie(object->cookie); + count++; + if ((count & 63) == 0) { + spin_unlock(&cache->object_list_lock); + cond_resched(); + spin_lock(&cache->object_list_lock); + } + } + + spin_unlock(&cache->object_list_lock); + _leave(" [%u objs]", count); +} + +/* + * Withdraw volumes. + */ +static void erofscache_withdraw_volumes(struct erofscache_cache *cache) +{ + _enter(""); + + for (;;) { + struct erofscache_volume *volume = NULL; + + spin_lock(&cache->object_list_lock); + if (!list_empty(&cache->volumes)) { + volume = list_first_entry(&cache->volumes, + struct erofscache_volume, cache_link); + list_del_init(&volume->cache_link); + } + spin_unlock(&cache->object_list_lock); + if (!volume) + break; + + erofscache_withdraw_volume(volume); + } + + _leave(""); +} + +/* + * Withdraw cache objects. + */ +void erofscache_withdraw_cache(struct erofscache_cache *cache) +{ + struct fscache_cache *fscache = cache->cache; + + pr_info("File cache on %s unregistering\n", fscache->name); + + fscache_withdraw_cache(fscache); + + /* we now have to destroy all the active objects pertaining to this + * cache - which we do by passing them off to thread pool to be + * disposed of */ + erofscache_withdraw_objects(cache); + fscache_wait_for_objects(fscache); + + erofscache_withdraw_volumes(cache); + cache->cache = NULL; + fscache_relinquish_cache(fscache); +} diff --git a/fs/erofscache/daemon.c b/fs/erofscache/daemon.c new file mode 100644 index 000000000000..863db9a61f37 --- /dev/null +++ b/fs/erofscache/daemon.c @@ -0,0 +1,525 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Daemon interface + * + * Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/sched.h> +#include <linux/completion.h> +#include <linux/slab.h> +#include <linux/fs.h> +#include <linux/file.h> +#include <linux/namei.h> +#include <linux/poll.h> +#include <linux/mount.h> +#include <linux/statfs.h> +#include <linux/ctype.h> +#include <linux/string.h> +#include <linux/fs_struct.h> +#include "internal.h" + +static int erofscache_daemon_open(struct inode *, struct file *); +static int erofscache_daemon_release(struct inode *, struct file *); +static ssize_t erofscache_daemon_read(struct file *, char __user *, size_t, + loff_t *); +static ssize_t erofscache_daemon_write(struct file *, const char __user *, + size_t, loff_t *); +static __poll_t erofscache_daemon_poll(struct file *, + struct poll_table_struct *); +static int erofscache_daemon_cull(struct erofscache_cache *, char *); +static int erofscache_daemon_debug(struct erofscache_cache *, char *); +static int erofscache_daemon_dir(struct erofscache_cache *, char *); +static int erofscache_daemon_inuse(struct erofscache_cache *, char *); +static int erofscache_daemon_secctx(struct erofscache_cache *, char *); +static int erofscache_daemon_tag(struct erofscache_cache *, char *); +static int erofscache_daemon_bind(struct erofscache_cache *, char *); +static void erofscache_daemon_unbind(struct erofscache_cache *); + +static unsigned long erofscache_open; + +const struct file_operations erofscache_daemon_fops = { + .owner = THIS_MODULE, + .open = erofscache_daemon_open, + .release = erofscache_daemon_release, + .read = erofscache_daemon_read, + .write = erofscache_daemon_write, + .poll = erofscache_daemon_poll, + .llseek = noop_llseek, +}; + +struct erofscache_daemon_cmd { + char name[8]; + int (*handler)(struct erofscache_cache *cache, char *args); +}; + +static const struct erofscache_daemon_cmd erofscache_daemon_cmds[] = { + { "bind", erofscache_daemon_bind }, + { "cull", erofscache_daemon_cull }, + { "debug", erofscache_daemon_debug }, + { "dir", erofscache_daemon_dir }, + { "inuse", erofscache_daemon_inuse }, + { "secctx", erofscache_daemon_secctx }, + { "tag", erofscache_daemon_tag }, + { "", NULL } +}; + + +/* + * Prepare a cache for caching. + */ +static int erofscache_daemon_open(struct inode *inode, struct file *file) +{ + struct erofscache_cache *cache; + + _enter(""); + + /* only the superuser may do this */ + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + /* the erofscache device may only be open once at a time */ + if (xchg(&erofscache_open, 1) == 1) + return -EBUSY; + + /* allocate a cache record */ + cache = kzalloc(sizeof(struct erofscache_cache), GFP_KERNEL); + if (!cache) { + erofscache_open = 0; + return -ENOMEM; + } + + mutex_init(&cache->daemon_mutex); + init_waitqueue_head(&cache->daemon_pollwq); + INIT_LIST_HEAD(&cache->volumes); + INIT_LIST_HEAD(&cache->object_list); + spin_lock_init(&cache->object_list_lock); + + file->private_data = cache; + cache->erofscached = file; + return 0; +} + +/* + * Release a cache. + */ +static int erofscache_daemon_release(struct inode *inode, struct file *file) +{ + struct erofscache_cache *cache = file->private_data; + + _enter(""); + + ASSERT(cache); + + set_bit(EROFSCACHE_DEAD, &cache->flags); + + erofscache_daemon_unbind(cache); + + /* clean up the control file interface */ + cache->erofscached = NULL; + file->private_data = NULL; + erofscache_open = 0; + + kfree(cache); + + _leave(""); + return 0; +} + +/* + * Read the cache state. + */ +static ssize_t erofscache_daemon_read(struct file *file, char __user *_buffer, + size_t buflen, loff_t *pos) +{ + struct erofscache_cache *cache = file->private_data; + unsigned long long b_released; + unsigned f_released; + char buffer[256]; + int n; + + //_enter(",,%zu,", buflen); + + if (!test_bit(EROFSCACHE_READY, &cache->flags)) + return 0; + + /* summarise */ + f_released = atomic_xchg(&cache->f_released, 0); + b_released = atomic_long_xchg(&cache->b_released, 0); + clear_bit(EROFSCACHE_STATE_CHANGED, &cache->flags); + + n = snprintf(buffer, sizeof(buffer), + "cull=%c" + " freleased=%x" + " breleased=%llx", + test_bit(EROFSCACHE_CULLING, &cache->flags) ? '1' : '0', + f_released, + b_released); + + if (n > buflen) + return -EMSGSIZE; + + if (copy_to_user(_buffer, buffer, n) != 0) + return -EFAULT; + + return n; +} + +/* + * Take a command from erofscached, parse it and act on it. + */ +static ssize_t erofscache_daemon_write(struct file *file, + const char __user *_data, + size_t datalen, + loff_t *pos) +{ + const struct erofscache_daemon_cmd *cmd; + struct erofscache_cache *cache = file->private_data; + ssize_t ret; + char *data, *args, *cp; + + //_enter(",,%zu,", datalen); + + ASSERT(cache); + + if (test_bit(EROFSCACHE_DEAD, &cache->flags)) + return -EIO; + + if (datalen > PAGE_SIZE - 1) + return -EOPNOTSUPP; + + /* drag the command string into the kernel so we can parse it */ + data = memdup_user_nul(_data, datalen); + if (IS_ERR(data)) + return PTR_ERR(data); + + ret = -EINVAL; + if (memchr(data, '\0', datalen)) + goto error; + + /* strip any newline */ + cp = memchr(data, '\n', datalen); + if (cp) { + if (cp == data) + goto error; + + *cp = '\0'; + } + + /* parse the command */ + ret = -EOPNOTSUPP; + + for (args = data; *args; args++) + if (isspace(*args)) + break; + if (*args) { + if (args == data) + goto error; + *args = '\0'; + args = skip_spaces(++args); + } + + /* run the appropriate command handler */ + for (cmd = erofscache_daemon_cmds; cmd->name[0]; cmd++) + if (strcmp(cmd->name, data) == 0) + goto found_command; + +error: + kfree(data); + //_leave(" = %zd", ret); + return ret; + +found_command: + mutex_lock(&cache->daemon_mutex); + + ret = -EIO; + if (!test_bit(EROFSCACHE_DEAD, &cache->flags)) + ret = cmd->handler(cache, args); + + mutex_unlock(&cache->daemon_mutex); + + if (ret == 0) + ret = datalen; + goto error; +} + +/* + * Poll for culling state + * - use EPOLLOUT to indicate culling state + */ +static __poll_t erofscache_daemon_poll(struct file *file, + struct poll_table_struct *poll) +{ + struct erofscache_cache *cache = file->private_data; + __poll_t mask; + + poll_wait(file, &cache->daemon_pollwq, poll); + mask = 0; + + if (test_bit(EROFSCACHE_STATE_CHANGED, &cache->flags)) + mask |= EPOLLIN; + + if (test_bit(EROFSCACHE_CULLING, &cache->flags)) + mask |= EPOLLOUT; + + return mask; +} + +/* + * Set the cache directory + * - command: "dir <name>" + */ +static int erofscache_daemon_dir(struct erofscache_cache *cache, char *args) +{ + char *dir; + + _enter(",%s", args); + + if (!*args) { + pr_err("Empty directory specified\n"); + return -EINVAL; + } + + if (cache->rootdirname) { + pr_err("Second cache directory specified\n"); + return -EEXIST; + } + + dir = kstrdup(args, GFP_KERNEL); + if (!dir) + return -ENOMEM; + + cache->rootdirname = dir; + return 0; +} + +/* + * Set the cache security context + * - command: "secctx <ctx>" + */ +static int erofscache_daemon_secctx(struct erofscache_cache *cache, char *args) +{ + char *secctx; + + _enter(",%s", args); + + if (!*args) { + pr_err("Empty security context specified\n"); + return -EINVAL; + } + + if (cache->secctx) { + pr_err("Second security context specified\n"); + return -EINVAL; + } + + secctx = kstrdup(args, GFP_KERNEL); + if (!secctx) + return -ENOMEM; + + cache->secctx = secctx; + return 0; +} + +/* + * Set the cache tag + * - command: "tag <name>" + */ +static int erofscache_daemon_tag(struct erofscache_cache *cache, char *args) +{ + char *tag; + + _enter(",%s", args); + + if (!*args) { + pr_err("Empty tag specified\n"); + return -EINVAL; + } + + if (cache->tag) + return -EEXIST; + + tag = kstrdup(args, GFP_KERNEL); + if (!tag) + return -ENOMEM; + + cache->tag = tag; + return 0; +} + +/* + * Request a node in the cache be culled from the current working directory + * - command: "cull <name>" + */ +static int erofscache_daemon_cull(struct erofscache_cache *cache, char *args) +{ + struct path path; + const struct cred *saved_cred; + int ret; + + _enter(",%s", args); + + if (strchr(args, '/')) + goto inval; + + if (!test_bit(EROFSCACHE_READY, &cache->flags)) { + pr_err("cull applied to unready cache\n"); + return -EIO; + } + + if (test_bit(EROFSCACHE_DEAD, &cache->flags)) { + pr_err("cull applied to dead cache\n"); + return -EIO; + } + + get_fs_pwd(current->fs, &path); + + if (!d_can_lookup(path.dentry)) + goto notdir; + + erofscache_begin_secure(cache, &saved_cred); + ret = erofscache_cull(cache, path.dentry, args); + erofscache_end_secure(cache, saved_cred); + + path_put(&path); + _leave(" = %d", ret); + return ret; + +notdir: + path_put(&path); + pr_err("cull command requires dirfd to be a directory\n"); + return -ENOTDIR; + +inval: + pr_err("cull command requires dirfd and filename\n"); + return -EINVAL; +} + +/* + * Set debugging mode + * - command: "debug <mask>" + */ +static int erofscache_daemon_debug(struct erofscache_cache *cache, char *args) +{ + unsigned long mask; + + _enter(",%s", args); + + mask = simple_strtoul(args, &args, 0); + if (args[0] != '\0') + goto inval; + + erofscache_debug = mask; + _leave(" = 0"); + return 0; + +inval: + pr_err("debug command requires mask\n"); + return -EINVAL; +} + +/* + * Find out whether an object in the current working directory is in use or not + * - command: "inuse <name>" + */ +static int erofscache_daemon_inuse(struct erofscache_cache *cache, char *args) +{ + struct path path; + const struct cred *saved_cred; + int ret; + + //_enter(",%s", args); + + if (strchr(args, '/')) + goto inval; + + if (!test_bit(EROFSCACHE_READY, &cache->flags)) { + pr_err("inuse applied to unready cache\n"); + return -EIO; + } + + if (test_bit(EROFSCACHE_DEAD, &cache->flags)) { + pr_err("inuse applied to dead cache\n"); + return -EIO; + } + + get_fs_pwd(current->fs, &path); + + if (!d_can_lookup(path.dentry)) + goto notdir; + + erofscache_begin_secure(cache, &saved_cred); + ret = erofscache_check_in_use(cache, path.dentry, args); + erofscache_end_secure(cache, saved_cred); + + path_put(&path); + //_leave(" = %d", ret); + return ret; + +notdir: + path_put(&path); + pr_err("inuse command requires dirfd to be a directory\n"); + return -ENOTDIR; + +inval: + pr_err("inuse command requires dirfd and filename\n"); + return -EINVAL; +} + +/* + * Bind a directory as a cache + */ +static int erofscache_daemon_bind(struct erofscache_cache *cache, char *args) +{ + if (*args) { + pr_err("'bind' command doesn't take an argument\n"); + return -EINVAL; + } + + if (!cache->rootdirname) { + pr_err("No cache directory specified\n"); + return -EINVAL; + } + + /* Don't permit already bound caches to be re-bound */ + if (test_bit(EROFSCACHE_READY, &cache->flags)) { + pr_err("Cache already bound\n"); + return -EBUSY; + } + + /* Make sure we have copies of the tag string */ + if (!cache->tag) { + /* + * The tag string is released by the fops->release() + * function, so we don't release it on error here + */ + cache->tag = kstrdup("Erofscache", GFP_KERNEL); + if (!cache->tag) + return -ENOMEM; + } + + return erofscache_add_cache(cache); +} + +/* + * Unbind a cache. + */ +static void erofscache_daemon_unbind(struct erofscache_cache *cache) +{ + _enter(""); + + if (test_bit(EROFSCACHE_READY, &cache->flags)) + erofscache_withdraw_cache(cache); + + erofscache_put_directory(cache->graveyard); + erofscache_put_directory(cache->store); + mntput(cache->mnt); + + kfree(cache->rootdirname); + kfree(cache->secctx); + kfree(cache->tag); + + _leave(""); +} diff --git a/fs/erofscache/error_inject.c b/fs/erofscache/error_inject.c new file mode 100644 index 000000000000..958b61198b36 --- /dev/null +++ b/fs/erofscache/error_inject.c @@ -0,0 +1,46 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Error injection handling. + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/sysctl.h> +#include "internal.h" + +unsigned int erofscache_error_injection_state; + +static struct ctl_table_header *erofscache_sysctl; +static struct ctl_table erofscache_sysctls[] = { + { + .procname = "error_injection", + .data = &erofscache_error_injection_state, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_douintvec, + }, + {} +}; + +static struct ctl_table erofscache_sysctls_root[] = { + { + .procname = "erofscache", + .mode = 0555, + .child = erofscache_sysctls, + }, + {} +}; + +int __init erofscache_register_error_injection(void) +{ + erofscache_sysctl = register_sysctl_table(erofscache_sysctls_root); + if (!erofscache_sysctl) + return -ENOMEM; + return 0; + +} + +void erofscache_unregister_error_injection(void) +{ + unregister_sysctl_table(erofscache_sysctl); +} diff --git a/fs/erofscache/interface.c b/fs/erofscache/interface.c new file mode 100644 index 000000000000..a4cb182dacdd --- /dev/null +++ b/fs/erofscache/interface.c @@ -0,0 +1,254 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* FS-Cache interface to Erofscache + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/slab.h> +#include <linux/mount.h> +#include <linux/xattr.h> +#include <linux/file.h> +#include <linux/falloc.h> +#include <trace/events/fscache.h> +#include "internal.h" + +static atomic_t erofscache_object_debug_id; + +/* + * Allocate a cache object record. + */ +static +struct erofscache_object *erofscache_alloc_object(struct fscache_cookie *cookie) +{ + struct fscache_volume *vcookie = cookie->volume; + struct erofscache_volume *volume = vcookie->cache_priv; + struct erofscache_object *object; + + _enter("{%s},%x,", vcookie->key, cookie->debug_id); + + object = kmem_cache_zalloc(erofscache_object_jar, GFP_KERNEL); + if (!object) + return NULL; + + refcount_set(&object->ref, 1); + + spin_lock_init(&object->lock); + INIT_LIST_HEAD(&object->cache_link); + object->volume = volume; + object->debug_id = atomic_inc_return(&erofscache_object_debug_id); + object->cookie = fscache_get_cookie(cookie, fscache_cookie_get_attach_object); + + fscache_count_object(vcookie->cache); + trace_erofscache_ref(object->debug_id, cookie->debug_id, 1, + erofscache_obj_new); + return object; +} + +/* + * Note that an object has been seen. + */ +void erofscache_see_object(struct erofscache_object *object, + enum erofscache_obj_ref_trace why) +{ + trace_erofscache_ref(object->debug_id, object->cookie->debug_id, + refcount_read(&object->ref), why); +} + +/* + * Increment the usage count on an object; + */ +struct erofscache_object *erofscache_grab_object(struct erofscache_object *object, + enum erofscache_obj_ref_trace why) +{ + int r; + + __refcount_inc(&object->ref, &r); + trace_erofscache_ref(object->debug_id, object->cookie->debug_id, r, why); + return object; +} + +/* + * dispose of a reference to an object + */ +void erofscache_put_object(struct erofscache_object *object, + enum erofscache_obj_ref_trace why) +{ + unsigned int object_debug_id = object->debug_id; + unsigned int cookie_debug_id = object->cookie->debug_id; + struct fscache_cache *cache; + bool done; + int r; + + done = __refcount_dec_and_test(&object->ref, &r); + trace_erofscache_ref(object_debug_id, cookie_debug_id, r, why); + if (done) { + _debug("- kill object OBJ%x", object_debug_id); + + ASSERTCMP(object->file, ==, NULL); + + kfree(object->d_name); + + cache = object->volume->cache->cache; + fscache_put_cookie(object->cookie, fscache_cookie_put_object); + object->cookie = NULL; + kmem_cache_free(erofscache_object_jar, object); + fscache_uncount_object(cache); + } + + _leave(""); +} + +/* + * Attempt to look up the nominated node in this cache + */ +static bool erofscache_lookup_cookie(struct fscache_cookie *cookie) +{ + struct erofscache_object *object; + struct erofscache_cache *cache = cookie->volume->cache->cache_priv; + const struct cred *saved_cred; + bool success; + + object = erofscache_alloc_object(cookie); + if (!object) + goto fail; + + _enter("{OBJ%x}", object->debug_id); + + if (!erofscache_cook_key(object)) + goto fail_put; + + cookie->cache_priv = object; + + erofscache_begin_secure(cache, &saved_cred); + + success = erofscache_look_up_object(object); + if (!success) + goto fail_withdraw; + + erofscache_see_object(object, erofscache_obj_see_lookup_cookie); + + spin_lock(&cache->object_list_lock); + list_add(&object->cache_link, &cache->object_list); + spin_unlock(&cache->object_list_lock); + // TODO: Do we need erofscache_adjust_size(object)? + + erofscache_end_secure(cache, saved_cred); + _leave(" = t"); + return true; + +fail_withdraw: + erofscache_end_secure(cache, saved_cred); + erofscache_see_object(object, erofscache_obj_see_lookup_failed); + fscache_caching_failed(cookie); + _debug("failed c=%08x o=%08x", cookie->debug_id, object->debug_id); + /* The caller holds an access count on the cookie, so we need them to + * drop it before we can withdraw the object. + */ + return false; + +fail_put: + erofscache_put_object(object, erofscache_obj_put_alloc_fail); +fail: + return false; +} + +/* + * Finalise and object and close the VFS structs that we have. + */ +static void erofscache_clean_up_object(struct erofscache_object *object, + struct erofscache_cache *cache) +{ + if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) { + erofscache_see_object(object, erofscache_obj_see_clean_delete); + _debug("- inval object OBJ%x", object->debug_id); + erofscache_delete_object(object, FSCACHE_OBJECT_WAS_RETIRED); + } + + erofscache_unmark_inode_in_use(object, object->file); + if (object->file) { + fput(object->file); + object->file = NULL; + } +} + +/* + * Withdraw caching for a cookie. + */ +static void erofscache_withdraw_cookie(struct fscache_cookie *cookie) +{ + struct erofscache_object *object = cookie->cache_priv; + struct erofscache_cache *cache = object->volume->cache; + const struct cred *saved_cred; + + _enter("o=%x", object->debug_id); + erofscache_see_object(object, erofscache_obj_see_withdraw_cookie); + + if (!list_empty(&object->cache_link)) { + spin_lock(&cache->object_list_lock); + erofscache_see_object(object, erofscache_obj_see_withdrawal); + list_del_init(&object->cache_link); + spin_unlock(&cache->object_list_lock); + } + + if (object->file) { + erofscache_begin_secure(cache, &saved_cred); + erofscache_clean_up_object(object, cache); + erofscache_end_secure(cache, saved_cred); + } + + cookie->cache_priv = NULL; + erofscache_put_object(object, erofscache_obj_put_detach); +} + +/* + * Invalidate the storage associated with a cookie. + */ +static bool erofscache_invalidate_cookie(struct fscache_cookie *cookie) +{ + struct erofscache_object *object = cookie->cache_priv; + struct erofscache_volume *volume = object->volume; + struct dentry *fan = volume->fanout[(u8)cookie->key_hash]; + struct file *file; + + _enter("o=%x,[%llu]", object->debug_id, object->cookie->object_size); + + if (!object->file) { + fscache_resume_after_invalidation(cookie); + _leave(" = t [light]"); + return true; + } + + /* Remove the VFS target and mark disabled */ + spin_lock(&object->lock); + + file = object->file; + object->file = NULL; + set_bit(FSCACHE_COOKIE_DISABLED, &object->cookie->flags); + + spin_unlock(&object->lock); + + /* Allow I/O to take place again */ + fscache_resume_after_invalidation(cookie); + + if (file) { + inode_lock_nested(d_inode(fan), I_MUTEX_PARENT); + erofscache_bury_object(volume->cache, object, fan, + file->f_path.dentry, + FSCACHE_OBJECT_INVALIDATED); + fput(file); + } + + _leave(" = t"); + return true; +} + +const struct fscache_cache_ops erofscache_cache_ops = { + .name = "erofscache", + .acquire_volume = erofscache_acquire_volume, + .free_volume = erofscache_free_volume, + .lookup_cookie = erofscache_lookup_cookie, + .withdraw_cookie = erofscache_withdraw_cookie, + .invalidate_cookie = erofscache_invalidate_cookie, + .begin_operation = erofscache_begin_operation, +}; diff --git a/fs/erofscache/internal.h b/fs/erofscache/internal.h new file mode 100644 index 000000000000..f7f00ba42f11 --- /dev/null +++ b/fs/erofscache/internal.h @@ -0,0 +1,349 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* Internal defs for erofs demand-load netfs cache on cache files. + * + * Copyright (C) 2022 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#ifdef pr_fmt +#undef pr_fmt +#endif + +#define pr_fmt(fmt) "Erofscache: " fmt + + +#include <linux/fscache-cache.h> +#include <linux/cred.h> +#include <linux/security.h> + +#define EROFSCACHE_DIO_BLOCK_SIZE 4096 + +struct erofscache_cache; +struct erofscache_object; + +/* + * Cached volume representation. + */ +struct erofscache_volume { + struct erofscache_cache *cache; + struct list_head cache_link; /* Link in cache->volumes */ + struct fscache_volume *vcookie; /* The netfs's representation */ + struct dentry *dentry; /* The volume dentry */ + struct dentry *fanout[256]; /* Fanout subdirs */ +}; + +/* + * Backing file state. + */ +struct erofscache_object { + struct fscache_cookie *cookie; /* Netfs data storage object cookie */ + struct erofscache_volume *volume; /* Cache volume that holds this object */ + struct list_head cache_link; /* Link in cache->*_list */ + struct file *file; /* The file representing this object */ + char *d_name; /* Backing file name */ + int debug_id; + spinlock_t lock; + refcount_t ref; + u8 d_name_len; /* Length of filename */ +}; + +/* + * Cache files cache definition + */ +struct erofscache_cache { + struct fscache_cache *cache; /* Cache cookie */ + struct vfsmount *mnt; /* mountpoint holding the cache */ + struct dentry *store; /* Directory into which live objects go */ + struct dentry *graveyard; /* directory into which dead objects go */ + struct file *erofscached; /* manager daemon handle */ + struct list_head volumes; /* List of volume objects */ + struct list_head object_list; /* List of active objects */ + spinlock_t object_list_lock; /* Lock for volumes and object_list */ + const struct cred *cache_cred; /* security override for accessing cache */ + struct mutex daemon_mutex; /* command serialisation mutex */ + wait_queue_head_t daemon_pollwq; /* poll waitqueue for daemon */ + unsigned bsize; /* cache's block size */ + unsigned bshift; /* ilog2(bsize) */ + atomic_t gravecounter; /* graveyard uniquifier */ + atomic_t f_released; /* number of objects released lately */ + atomic_long_t b_released; /* number of blocks released lately */ + unsigned long flags; +#define EROFSCACHE_READY 0 /* T if cache prepared */ +#define EROFSCACHE_DEAD 1 /* T if cache dead */ +#define EROFSCACHE_CULLING 2 /* T if cull engaged */ +#define EROFSCACHE_STATE_CHANGED 3 /* T if state changed (poll trigger) */ + char *rootdirname; /* name of cache root directory */ + char *secctx; /* LSM security context */ + char *tag; /* cache binding tag */ +}; + +#include <trace/events/erofscache.h> + +static inline +struct file *erofscache_cres_file(struct netfs_cache_resources *cres) +{ + return cres->cache_priv2; +} + +static inline +struct erofscache_object *erofscache_cres_object(struct netfs_cache_resources *cres) +{ + return fscache_cres_cookie(cres)->cache_priv; +} + +/* + * note change of state for daemon + */ +static inline void erofscache_state_changed(struct erofscache_cache *cache) +{ + set_bit(EROFSCACHE_STATE_CHANGED, &cache->flags); + wake_up_all(&cache->daemon_pollwq); +} + +/* + * cache.c + */ +extern int erofscache_add_cache(struct erofscache_cache *cache); +extern void erofscache_withdraw_cache(struct erofscache_cache *cache); + +/* + * daemon.c + */ +extern const struct file_operations erofscache_daemon_fops; + +/* + * error_inject.c + */ +#ifdef CONFIG_EROFSCACHE_ERROR_INJECTION +extern unsigned int erofscache_error_injection_state; +extern int erofscache_register_error_injection(void); +extern void erofscache_unregister_error_injection(void); + +#else +#define erofscache_error_injection_state 0 + +static inline int erofscache_register_error_injection(void) +{ + return 0; +} + +static inline void erofscache_unregister_error_injection(void) +{ +} +#endif + + +static inline int erofscache_inject_read_error(void) +{ + return erofscache_error_injection_state & 2 ? -EIO : 0; +} + +static inline int erofscache_inject_remove_error(void) +{ + return erofscache_error_injection_state & 2 ? -EIO : 0; +} + +/* + * interface.c + */ +extern const struct fscache_cache_ops erofscache_cache_ops; +extern void erofscache_see_object(struct erofscache_object *object, + enum erofscache_obj_ref_trace why); +extern struct erofscache_object *erofscache_grab_object(struct erofscache_object *object, + enum erofscache_obj_ref_trace why); +extern void erofscache_put_object(struct erofscache_object *object, + enum erofscache_obj_ref_trace why); + +/* + * io.c + */ +extern bool erofscache_begin_operation(struct netfs_cache_resources *cres, + enum fscache_want_state want_state); + +/* + * key.c + */ +extern bool erofscache_cook_key(struct erofscache_object *object); + +/* + * main.c + */ +extern struct kmem_cache *erofscache_object_jar; + +/* + * namei.c + */ +extern void erofscache_unmark_inode_in_use(struct erofscache_object *object, + struct file *file); +extern int erofscache_bury_object(struct erofscache_cache *cache, + struct erofscache_object *object, + struct dentry *dir, + struct dentry *rep, + enum fscache_why_object_killed why); +extern int erofscache_delete_object(struct erofscache_object *object, + enum fscache_why_object_killed why); +extern bool erofscache_look_up_object(struct erofscache_object *object); +extern struct dentry *erofscache_get_directory(struct erofscache_cache *cache, + struct dentry *dir, + const char *name); +extern void erofscache_put_directory(struct dentry *dir); + +extern int erofscache_cull(struct erofscache_cache *cache, struct dentry *dir, + char *filename); + +extern int erofscache_check_in_use(struct erofscache_cache *cache, + struct dentry *dir, char *filename); + +/* + * security.c + */ +extern int erofscache_get_security_ID(struct erofscache_cache *cache); +extern int erofscache_determine_cache_security(struct erofscache_cache *cache, + struct dentry *root, + const struct cred **_saved_cred); + +static inline void erofscache_begin_secure(struct erofscache_cache *cache, + const struct cred **_saved_cred) +{ + *_saved_cred = override_creds(cache->cache_cred); +} + +static inline void erofscache_end_secure(struct erofscache_cache *cache, + const struct cred *saved_cred) +{ + revert_creds(saved_cred); +} + +/* + * volume.c + */ +void erofscache_acquire_volume(struct fscache_volume *volume); +void erofscache_free_volume(struct fscache_volume *volume); +void erofscache_withdraw_volume(struct erofscache_volume *volume); + +/* + * xattr.c + */ +extern int erofscache_check_auxdata(struct erofscache_object *object, + struct file *file); +extern int erofscache_remove_object_xattr(struct erofscache_cache *cache, + struct erofscache_object *object, + struct dentry *dentry); +extern int erofscache_check_volume_xattr(struct erofscache_volume *volume); + +/* + * Error handling + */ +#define erofscache_io_error(___cache, FMT, ...) \ +do { \ + pr_err("I/O Error: " FMT"\n", ##__VA_ARGS__); \ + fscache_io_error((___cache)->cache); \ + set_bit(EROFSCACHE_DEAD, &(___cache)->flags); \ +} while (0) + +#define erofscache_io_error_obj(object, FMT, ...) \ +do { \ + struct erofscache_cache *___cache; \ + \ + ___cache = (object)->volume->cache; \ + erofscache_io_error(___cache, FMT " [o=%08x]", ##__VA_ARGS__, \ + (object)->debug_id); \ +} while (0) + + +/* + * Debug tracing + */ +extern unsigned erofscache_debug; +#define EROFSCACHE_DEBUG_KENTER 1 +#define EROFSCACHE_DEBUG_KLEAVE 2 +#define EROFSCACHE_DEBUG_KDEBUG 4 + +#define dbgprintk(FMT, ...) \ + printk(KERN_DEBUG "[%-6.6s] "FMT"\n", current->comm, ##__VA_ARGS__) + +#define kenter(FMT, ...) dbgprintk("==> %s("FMT")", __func__, ##__VA_ARGS__) +#define kleave(FMT, ...) dbgprintk("<== %s()"FMT"", __func__, ##__VA_ARGS__) +#define kdebug(FMT, ...) dbgprintk(FMT, ##__VA_ARGS__) + + +#if defined(__KDEBUG) +#define _enter(FMT, ...) kenter(FMT, ##__VA_ARGS__) +#define _leave(FMT, ...) kleave(FMT, ##__VA_ARGS__) +#define _debug(FMT, ...) kdebug(FMT, ##__VA_ARGS__) + +#elif defined(CONFIG_EROFSCACHE_DEBUG) +#define _enter(FMT, ...) \ +do { \ + if (erofscache_debug & EROFSCACHE_DEBUG_KENTER) \ + kenter(FMT, ##__VA_ARGS__); \ +} while (0) + +#define _leave(FMT, ...) \ +do { \ + if (erofscache_debug & EROFSCACHE_DEBUG_KLEAVE) \ + kleave(FMT, ##__VA_ARGS__); \ +} while (0) + +#define _debug(FMT, ...) \ +do { \ + if (erofscache_debug & EROFSCACHE_DEBUG_KDEBUG) \ + kdebug(FMT, ##__VA_ARGS__); \ +} while (0) + +#else +#define _enter(FMT, ...) no_printk("==> %s("FMT")", __func__, ##__VA_ARGS__) +#define _leave(FMT, ...) no_printk("<== %s()"FMT"", __func__, ##__VA_ARGS__) +#define _debug(FMT, ...) no_printk(FMT, ##__VA_ARGS__) +#endif + +#if 1 /* defined(__KDEBUGALL) */ + +#define ASSERT(X) \ +do { \ + if (unlikely(!(X))) { \ + pr_err("\n"); \ + pr_err("Assertion failed\n"); \ + BUG(); \ + } \ +} while (0) + +#define ASSERTCMP(X, OP, Y) \ +do { \ + if (unlikely(!((X) OP (Y)))) { \ + pr_err("\n"); \ + pr_err("Assertion failed\n"); \ + pr_err("%lx " #OP " %lx is false\n", \ + (unsigned long)(X), (unsigned long)(Y)); \ + BUG(); \ + } \ +} while (0) + +#define ASSERTIF(C, X) \ +do { \ + if (unlikely((C) && !(X))) { \ + pr_err("\n"); \ + pr_err("Assertion failed\n"); \ + BUG(); \ + } \ +} while (0) + +#define ASSERTIFCMP(C, X, OP, Y) \ +do { \ + if (unlikely((C) && !((X) OP (Y)))) { \ + pr_err("\n"); \ + pr_err("Assertion failed\n"); \ + pr_err("%lx " #OP " %lx is false\n", \ + (unsigned long)(X), (unsigned long)(Y)); \ + BUG(); \ + } \ +} while (0) + +#else + +#define ASSERT(X) do {} while (0) +#define ASSERTCMP(X, OP, Y) do {} while (0) +#define ASSERTIF(C, X) do {} while (0) +#define ASSERTIFCMP(C, X, OP, Y) do {} while (0) + +#endif diff --git a/fs/erofscache/io.c b/fs/erofscache/io.c new file mode 100644 index 000000000000..0234e9a2a992 --- /dev/null +++ b/fs/erofscache/io.c @@ -0,0 +1,339 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* kiocb-using read/write + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/mount.h> +#include <linux/slab.h> +#include <linux/file.h> +#include <linux/uio.h> +#include <linux/falloc.h> +#include <linux/sched/mm.h> +#include <trace/events/fscache.h> +#include "internal.h" + +struct erofscache_kiocb { + struct kiocb iocb; + refcount_t ki_refcnt; + loff_t start; + union { + size_t skipped; + size_t len; + }; + struct erofscache_object *object; + netfs_io_terminated_t term_func; + void *term_func_priv; + bool was_async; + unsigned int inval_counter; /* Copy of cookie->inval_counter */ + u64 b_writing; +}; + +static inline void erofscache_put_kiocb(struct erofscache_kiocb *ki) +{ + if (refcount_dec_and_test(&ki->ki_refcnt)) { + erofscache_put_object(ki->object, erofscache_obj_put_ioreq); + fput(ki->iocb.ki_filp); + kfree(ki); + } +} + +/* + * Handle completion of a read from the cache. + */ +static void erofscache_read_complete(struct kiocb *iocb, long ret) +{ + struct erofscache_kiocb *ki = container_of(iocb, struct erofscache_kiocb, iocb); + struct inode *inode = file_inode(ki->iocb.ki_filp); + + _enter("%ld", ret); + + if (ret < 0) + trace_erofscache_io_error(ki->object, inode, ret, + erofscache_trace_read_error); + + if (ki->term_func) { + if (ret >= 0) { + if (ki->object->cookie->inval_counter == ki->inval_counter) + ki->skipped += ret; + else + ret = -ESTALE; + } + + ki->term_func(ki->term_func_priv, ret, ki->was_async); + } + + erofscache_put_kiocb(ki); +} + +/* + * Initiate a read from the cache. + */ +static int erofscache_read(struct netfs_cache_resources *cres, + loff_t start_pos, + struct iov_iter *iter, + enum netfs_read_from_hole read_hole, + netfs_io_terminated_t term_func, + void *term_func_priv) +{ + struct erofscache_object *object; + struct erofscache_kiocb *ki; + struct file *file; + unsigned int old_nofs; + ssize_t ret = -ENOBUFS; + size_t len = iov_iter_count(iter), skipped = 0; + + if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ)) + goto presubmission_error; + + fscache_count_read(); + object = erofscache_cres_object(cres); + file = erofscache_cres_file(cres); + + _enter("%pD,%li,%llx,%zx/%llx", + file, file_inode(file)->i_ino, start_pos, len, + i_size_read(file_inode(file))); + + /* If the caller asked us to seek for data before doing the read, then + * we should do that now. If we find a gap, we fill it with zeros. + */ + if (read_hole != NETFS_READ_HOLE_IGNORE) { + loff_t off = start_pos, off2; + + off2 = erofscache_inject_read_error(); + if (off2 == 0) + off2 = vfs_llseek(file, off, SEEK_DATA); + if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO && off2 != -ENXIO) { + skipped = 0; + ret = off2; + goto presubmission_error; + } + + if (off2 == -ENXIO || off2 >= start_pos + len) { + /* The region is beyond the EOF or there's no more data + * in the region, so clear the rest of the buffer and + * return success. + */ + ret = -ENODATA; + if (read_hole == NETFS_READ_HOLE_FAIL) + goto presubmission_error; + + iov_iter_zero(len, iter); + skipped = len; + ret = 0; + goto presubmission_error; + } + + skipped = off2 - off; + iov_iter_zero(skipped, iter); + } + + ret = -ENOMEM; + ki = kzalloc(sizeof(struct erofscache_kiocb), GFP_KERNEL); + if (!ki) + goto presubmission_error; + + refcount_set(&ki->ki_refcnt, 2); + ki->iocb.ki_filp = file; + ki->iocb.ki_pos = start_pos + skipped; + ki->iocb.ki_flags = IOCB_DIRECT; + ki->iocb.ki_hint = ki_hint_validate(file_write_hint(file)); + ki->iocb.ki_ioprio = get_current_ioprio(); + ki->skipped = skipped; + ki->object = object; + ki->inval_counter = cres->inval_counter; + ki->term_func = term_func; + ki->term_func_priv = term_func_priv; + ki->was_async = true; + + if (ki->term_func) + ki->iocb.ki_complete = erofscache_read_complete; + + get_file(ki->iocb.ki_filp); + erofscache_grab_object(object, erofscache_obj_get_ioreq); + + trace_erofscache_read(object, file_inode(file), ki->iocb.ki_pos, len - skipped); + old_nofs = memalloc_nofs_save(); + ret = erofscache_inject_read_error(); + if (ret == 0) + ret = vfs_iocb_iter_read(file, &ki->iocb, iter); + memalloc_nofs_restore(old_nofs); + switch (ret) { + case -EIOCBQUEUED: + goto in_progress; + + case -ERESTARTSYS: + case -ERESTARTNOINTR: + case -ERESTARTNOHAND: + case -ERESTART_RESTARTBLOCK: + /* There's no easy way to restart the syscall since other AIO's + * may be already running. Just fail this IO with EINTR. + */ + ret = -EINTR; + fallthrough; + default: + ki->was_async = false; + erofscache_read_complete(&ki->iocb, ret); + if (ret > 0) + ret = 0; + break; + } + +in_progress: + erofscache_put_kiocb(ki); + _leave(" = %zd", ret); + return ret; + +presubmission_error: + if (term_func) + term_func(term_func_priv, ret < 0 ? ret : skipped, false); + return ret; +} + +/* + * Prepare a read operation, shortening it to a cached/uncached + * boundary as appropriate. + */ +static enum netfs_read_source erofscache_prepare_read(struct netfs_read_subrequest *subreq, + loff_t i_size) +{ + enum erofscache_prepare_read_trace why; + struct netfs_read_request *rreq = subreq->rreq; + struct netfs_cache_resources *cres = &rreq->cache_resources; + struct erofscache_object *object; + struct erofscache_cache *cache; + struct fscache_cookie *cookie = fscache_cres_cookie(cres); + const struct cred *saved_cred; + struct file *file = erofscache_cres_file(cres); + enum netfs_read_source ret = NETFS_DOWNLOAD_FROM_SERVER; + loff_t off, to; + ino_t ino = file ? file_inode(file)->i_ino : 0; + + _enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size); + + if (subreq->start >= i_size) { + ret = NETFS_FILL_WITH_ZEROES; + why = erofscache_trace_read_after_eof; + goto out_no_object; + } + + if (test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags)) { + __set_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags); + why = erofscache_trace_read_no_data; + goto out_no_object; + } + + /* The object and the file may be being created in the background. */ + if (!file) { + why = erofscache_trace_read_no_file; + if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ)) + goto out_no_object; + file = erofscache_cres_file(cres); + if (!file) + goto out_no_object; + ino = file_inode(file)->i_ino; + } + + object = erofscache_cres_object(cres); + cache = object->volume->cache; + erofscache_begin_secure(cache, &saved_cred); + + off = erofscache_inject_read_error(); + if (off == 0) + off = vfs_llseek(file, subreq->start, SEEK_DATA); + if (off < 0 && off >= (loff_t)-MAX_ERRNO) { + if (off == (loff_t)-ENXIO) { + why = erofscache_trace_read_seek_nxio; + goto out; + } + trace_erofscache_io_error(object, file_inode(file), off, + erofscache_trace_seek_error); + why = erofscache_trace_read_seek_error; + goto out; + } + + if (off >= subreq->start + subreq->len) { + why = erofscache_trace_read_found_hole; + goto out; + } + + if (off > subreq->start) { + off = round_up(off, cache->bsize); + subreq->len = off - subreq->start; + why = erofscache_trace_read_found_part; + goto out; + } + + to = erofscache_inject_read_error(); + if (to == 0) + to = vfs_llseek(file, subreq->start, SEEK_HOLE); + if (to < 0 && to >= (loff_t)-MAX_ERRNO) { + trace_erofscache_io_error(object, file_inode(file), to, + erofscache_trace_seek_error); + why = erofscache_trace_read_seek_error; + goto out; + } + + if (to < subreq->start + subreq->len) { + if (subreq->start + subreq->len >= i_size) + to = round_up(to, cache->bsize); + else + to = round_down(to, cache->bsize); + subreq->len = to - subreq->start; + } + + why = erofscache_trace_read_have_data; + ret = NETFS_READ_FROM_CACHE; + goto out; + +out: + erofscache_end_secure(cache, saved_cred); +out_no_object: + trace_erofscache_prep_read(subreq, ret, why, ino); + return ret; +} + +/* + * Clean up an operation. + */ +static void erofscache_end_operation(struct netfs_cache_resources *cres) +{ + struct file *file = erofscache_cres_file(cres); + + if (file) + fput(file); + fscache_end_cookie_access(fscache_cres_cookie(cres), fscache_access_io_end); +} + +static const struct netfs_cache_ops erofscache_netfs_cache_ops = { + .end_operation = erofscache_end_operation, + .read = erofscache_read, + .prepare_read = erofscache_prepare_read, +}; + +/* + * Open the cache file when beginning a cache operation. + */ +bool erofscache_begin_operation(struct netfs_cache_resources *cres, + enum fscache_want_state want_state) +{ + struct erofscache_object *object = erofscache_cres_object(cres); + + if (!erofscache_cres_file(cres)) { + cres->ops = &erofscache_netfs_cache_ops; + if (object->file) { + spin_lock(&object->lock); + if (!cres->cache_priv2 && object->file) + cres->cache_priv2 = get_file(object->file); + spin_unlock(&object->lock); + } + } + + if (!erofscache_cres_file(cres) && want_state != FSCACHE_WANT_PARAMS) { + pr_err("failed to get cres->file\n"); + return false; + } + + return true; +} diff --git a/fs/erofscache/key.c b/fs/erofscache/key.c new file mode 100644 index 000000000000..6bad2d461d42 --- /dev/null +++ b/fs/erofscache/key.c @@ -0,0 +1,138 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Key to pathname encoder + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/slab.h> +#include "internal.h" + +static const char erofscache_charmap[64] = + "0123456789" /* 0 - 9 */ + "abcdefghijklmnopqrstuvwxyz" /* 10 - 35 */ + "ABCDEFGHIJKLMNOPQRSTUVWXYZ" /* 36 - 61 */ + "_-" /* 62 - 63 */ + ; + +static const char erofscache_filecharmap[256] = { + /* we skip space and tab and control chars */ + [33 ... 46] = 1, /* '!' -> '.' */ + /* we skip '/' as it's significant to pathwalk */ + [48 ... 127] = 1, /* '0' -> '~' */ +}; + +static inline unsigned int how_many_hex_digits(unsigned int x) +{ + return x ? round_up(ilog2(x) + 1, 4) / 4 : 0; +} + +/* + * turn the raw key into something cooked + * - the key may be up to NAME_MAX in length (including the length word) + * - "base64" encode the strange keys, mapping 3 bytes of raw to four of + * cooked + * - need to cut the cooked key into 252 char lengths (189 raw bytes) + */ +bool erofscache_cook_key(struct erofscache_object *object) +{ + const u8 *key = fscache_get_key(object->cookie), *kend; + unsigned char ch; + unsigned int acc, i, n, nle, nbe, keylen = object->cookie->key_len; + unsigned int b64len, len, print, pad; + char *name, sep; + + _enter(",%u,%*phN", keylen, keylen, key); + + BUG_ON(keylen > NAME_MAX - 3); + + print = 1; + for (i = 0; i < keylen; i++) { + ch = key[i]; + print &= erofscache_filecharmap[ch]; + } + + /* If the path is usable ASCII, then we render it directly */ + if (print) { + len = 1 + keylen; + name = kmalloc(len + 1, GFP_KERNEL); + if (!name) + return false; + + name[0] = 'D'; /* Data object type, string encoding */ + memcpy(name + 1, key, keylen); + goto success; + } + + /* See if it makes sense to encode it as "hex,hex,hex" for each 32-bit + * chunk. We rely on the key having been padded out to a whole number + * of 32-bit words. + */ + n = round_up(keylen, 4); + nbe = nle = 0; + for (i = 0; i < n; i += 4) { + u32 be = be32_to_cpu(*(__be32 *)(key + i)); + u32 le = le32_to_cpu(*(__le32 *)(key + i)); + + nbe += 1 + how_many_hex_digits(be); + nle += 1 + how_many_hex_digits(le); + } + + b64len = DIV_ROUND_UP(keylen, 3); + pad = b64len * 3 - keylen; + b64len = 2 + b64len * 4; /* Length if we base64-encode it */ + _debug("len=%u nbe=%u nle=%u b64=%u", keylen, nbe, nle, b64len); + if (nbe < b64len || nle < b64len) { + unsigned int nlen = min(nbe, nle) + 1; + name = kmalloc(nlen, GFP_KERNEL); + if (!name) + return false; + sep = (nbe <= nle) ? 'S' : 'T'; /* Encoding indicator */ + len = 0; + for (i = 0; i < n; i += 4) { + u32 x; + if (nbe <= nle) + x = be32_to_cpu(*(__be32 *)(key + i)); + else + x = le32_to_cpu(*(__le32 *)(key + i)); + name[len++] = sep; + if (x != 0) + len += snprintf(name + len, nlen - len, "%x", x); + sep = ','; + } + goto success; + } + + /* We need to base64-encode it */ + name = kmalloc(b64len + 1, GFP_KERNEL); + if (!name) + return false; + + name[0] = 'E'; + name[1] = '0' + pad; + len = 2; + kend = key + keylen; + do { + acc = *key++; + if (key < kend) { + acc |= *key++ << 8; + if (key < kend) + acc |= *key++ << 16; + } + + name[len++] = erofscache_charmap[acc & 63]; + acc >>= 6; + name[len++] = erofscache_charmap[acc & 63]; + acc >>= 6; + name[len++] = erofscache_charmap[acc & 63]; + acc >>= 6; + name[len++] = erofscache_charmap[acc & 63]; + } while (key < kend); + +success: + name[len] = 0; + object->d_name = name; + object->d_name_len = len; + _leave(" = %s", object->d_name); + return true; +} diff --git a/fs/erofscache/main.c b/fs/erofscache/main.c new file mode 100644 index 000000000000..8daa4f06d09f --- /dev/null +++ b/fs/erofscache/main.c @@ -0,0 +1,93 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Network filesystem caching backend to use cache files on a premounted + * filesystem + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/sched.h> +#include <linux/completion.h> +#include <linux/slab.h> +#include <linux/fs.h> +#include <linux/file.h> +#include <linux/namei.h> +#include <linux/mount.h> +#include <linux/statfs.h> +#include <linux/sysctl.h> +#include <linux/miscdevice.h> +#include <linux/netfs.h> +#include <trace/events/netfs.h> +#define CREATE_TRACE_POINTS +#include "internal.h" + +unsigned erofscache_debug; +module_param_named(debug, erofscache_debug, uint, S_IWUSR | S_IRUGO); +MODULE_PARM_DESC(erofscache_debug, "Erofscache debugging mask"); + +MODULE_DESCRIPTION("Mounted-filesystem based cache"); +MODULE_AUTHOR("Red Hat, Inc."); +MODULE_LICENSE("GPL"); + +struct kmem_cache *erofscache_object_jar; + +static struct miscdevice erofscache_dev = { + .minor = MISC_DYNAMIC_MINOR, + .name = "erofscache", + .fops = &erofscache_daemon_fops, +}; + +/* + * initialise the fs caching module + */ +static int __init erofscache_init(void) +{ + int ret; + + ret = erofscache_register_error_injection(); + if (ret < 0) + goto error_einj; + ret = misc_register(&erofscache_dev); + if (ret < 0) + goto error_dev; + + /* create an object jar */ + ret = -ENOMEM; + erofscache_object_jar = + kmem_cache_create("erofscache_object_jar", + sizeof(struct erofscache_object), + 0, SLAB_HWCACHE_ALIGN, NULL); + if (!erofscache_object_jar) { + pr_notice("Failed to allocate an object jar\n"); + goto error_object_jar; + } + + pr_info("Loaded\n"); + return 0; + +error_object_jar: + misc_deregister(&erofscache_dev); +error_dev: + erofscache_unregister_error_injection(); +error_einj: + pr_err("failed to register: %d\n", ret); + return ret; +} + +fs_initcall(erofscache_init); + +/* + * clean up on module removal + */ +static void __exit erofscache_exit(void) +{ + pr_info("Unloading\n"); + + kmem_cache_destroy(erofscache_object_jar); + misc_deregister(&erofscache_dev); + erofscache_unregister_error_injection(); +} + +module_exit(erofscache_exit); diff --git a/fs/erofscache/namei.c b/fs/erofscache/namei.c new file mode 100644 index 000000000000..28c3f11c0fae --- /dev/null +++ b/fs/erofscache/namei.c @@ -0,0 +1,635 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Erofscache path walking and related routines + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/fs.h> +#include <linux/namei.h> +#include "internal.h" + +/* + * Mark the backing file as being a cache file if it's not already in use. The + * mark tells the culling request command that it's not allowed to cull the + * file or directory. The caller must hold the inode lock. + */ +static bool __erofscache_mark_inode_in_use(struct erofscache_object *object, + struct dentry *dentry) +{ + struct inode *inode = d_backing_inode(dentry); + bool can_use = false; + + if (!(inode->i_flags & S_KERNEL_FILE)) { + inode->i_flags |= S_KERNEL_FILE; + trace_erofscache_mark_active(object, inode); + can_use = true; + } else { + trace_erofscache_mark_failed(object, inode); + pr_notice("erofscache: Inode already in use: %pd (B=%lx)\n", + dentry, inode->i_ino); + } + + return can_use; +} + +static bool erofscache_mark_inode_in_use(struct erofscache_object *object, + struct dentry *dentry) +{ + struct inode *inode = d_backing_inode(dentry); + bool can_use; + + inode_lock(inode); + can_use = __erofscache_mark_inode_in_use(object, dentry); + inode_unlock(inode); + return can_use; +} + +/* + * Unmark a backing inode. The caller must hold the inode lock. + */ +static void __erofscache_unmark_inode_in_use(struct erofscache_object *object, + struct dentry *dentry) +{ + struct inode *inode = d_backing_inode(dentry); + + inode->i_flags &= ~S_KERNEL_FILE; + trace_erofscache_mark_inactive(object, inode); +} + +/* + * Unmark a backing inode and tell erofscached that there's something that can + * be culled. + */ +void erofscache_unmark_inode_in_use(struct erofscache_object *object, + struct file *file) +{ + struct erofscache_cache *cache = object->volume->cache; + struct inode *inode = file_inode(file); + + if (inode) { + inode_lock(inode); + __erofscache_unmark_inode_in_use(object, file->f_path.dentry); + inode_unlock(inode); + + atomic_long_add(inode->i_blocks, &cache->b_released); + if (atomic_inc_return(&cache->f_released)) + erofscache_state_changed(cache); + } +} + +/* + * get a subdirectory + */ +struct dentry *erofscache_get_directory(struct erofscache_cache *cache, + struct dentry *dir, + const char *dirname) +{ + struct dentry *subdir; + int ret; + + _enter(",,%s", dirname); + + /* search the current directory for the element name */ + inode_lock_nested(d_inode(dir), I_MUTEX_PARENT); + + ret = erofscache_inject_read_error(); + if (ret == 0) + subdir = lookup_one_len(dirname, dir, strlen(dirname)); + else + subdir = ERR_PTR(ret); + trace_erofscache_lookup(NULL, dir, subdir); + if (IS_ERR(subdir)) { + trace_erofscache_vfs_error(NULL, d_backing_inode(dir), + PTR_ERR(subdir), + erofscache_trace_lookup_error); + if (PTR_ERR(subdir) == -ENOMEM) + goto nomem_d_alloc; + goto lookup_error; + } + + _debug("subdir -> %pd %s", + subdir, d_backing_inode(subdir) ? "positive" : "negative"); + + /* TODO: Do we need to create the subdir if it doesn't exist? */ + if (d_is_negative(subdir)) + goto enoent; + + /* Tell rmdir() it's not allowed to delete the subdir */ + inode_lock(d_inode(subdir)); + inode_unlock(d_inode(dir)); + + if (!__erofscache_mark_inode_in_use(NULL, subdir)) + goto mark_error; + + inode_unlock(d_inode(subdir)); + + /* we need to make sure the subdir is a directory */ + ASSERT(d_backing_inode(subdir)); + + if (!d_can_lookup(subdir)) { + pr_err("%s is not a directory\n", dirname); + ret = -EIO; + goto check_error; + } + + ret = -EPERM; + if (!(d_backing_inode(subdir)->i_opflags & IOP_XATTR) || + !d_backing_inode(subdir)->i_op->lookup || + !d_backing_inode(subdir)->i_op->rename || + !d_backing_inode(subdir)->i_op->rmdir || + !d_backing_inode(subdir)->i_op->unlink) + goto check_error; + + _leave(" = [%lu]", d_backing_inode(subdir)->i_ino); + return subdir; + +check_error: + erofscache_put_directory(subdir); + _leave(" = %d [check]", ret); + return ERR_PTR(ret); + +mark_error: + inode_unlock(d_inode(subdir)); + dput(subdir); + return ERR_PTR(-EBUSY); + +enoent: + inode_unlock(d_inode(dir)); + dput(subdir); + pr_err("No such directory %s\n", dirname); + return ERR_PTR(-ENOENT); + +lookup_error: + inode_unlock(d_inode(dir)); + ret = PTR_ERR(subdir); + pr_err("Lookup %s failed with error %d\n", dirname, ret); + return ERR_PTR(ret); + +nomem_d_alloc: + inode_unlock(d_inode(dir)); + _leave(" = -ENOMEM"); + return ERR_PTR(-ENOMEM); +} + +/* + * Put a subdirectory. + */ +void erofscache_put_directory(struct dentry *dir) +{ + if (dir) { + inode_lock(dir->d_inode); + __erofscache_unmark_inode_in_use(NULL, dir); + inode_unlock(dir->d_inode); + dput(dir); + } +} + +/* + * Remove a regular file from the cache. + */ +static int erofscache_unlink(struct erofscache_cache *cache, + struct erofscache_object *object, + struct dentry *dir, struct dentry *dentry, + enum fscache_why_object_killed why) +{ + struct path path = { + .mnt = cache->mnt, + .dentry = dir, + }; + int ret; + + trace_erofscache_unlink(object, d_inode(dentry)->i_ino, why); + ret = security_path_unlink(&path, dentry); + if (ret < 0) { + erofscache_io_error(cache, "Unlink security error"); + return ret; + } + + ret = erofscache_inject_remove_error(); + if (ret == 0) { + ret = vfs_unlink(&init_user_ns, d_backing_inode(dir), dentry, NULL); + if (ret == -EIO) + erofscache_io_error(cache, "Unlink failed"); + } + if (ret != 0) + trace_erofscache_vfs_error(object, d_backing_inode(dir), ret, + erofscache_trace_unlink_error); + return ret; +} + +/* + * Delete an object representation from the cache + * - File backed objects are unlinked + * - Directory backed objects are stuffed into the graveyard for userspace to + * delete + */ +int erofscache_bury_object(struct erofscache_cache *cache, + struct erofscache_object *object, + struct dentry *dir, + struct dentry *rep, + enum fscache_why_object_killed why) +{ + struct dentry *grave, *trap; + struct path path, path_to_graveyard; + char nbuffer[8 + 8 + 1]; + int ret; + + _enter(",'%pd','%pd'", dir, rep); + + if (rep->d_parent != dir) { + inode_unlock(d_inode(dir)); + _leave(" = -ESTALE"); + return -ESTALE; + } + + /* non-directories can just be unlinked */ + if (!d_is_dir(rep)) { + dget(rep); /* Stop the dentry being negated if it's only pinned + * by a file struct. + */ + ret = erofscache_unlink(cache, object, dir, rep, why); + dput(rep); + + inode_unlock(d_inode(dir)); + _leave(" = %d", ret); + return ret; + } + + /* directories have to be moved to the graveyard */ + _debug("move stale object to graveyard"); + inode_unlock(d_inode(dir)); + +try_again: + /* first step is to make up a grave dentry in the graveyard */ + sprintf(nbuffer, "%08x%08x", + (uint32_t) ktime_get_real_seconds(), + (uint32_t) atomic_inc_return(&cache->gravecounter)); + + /* do the multiway lock magic */ + trap = lock_rename(cache->graveyard, dir); + + /* do some checks before getting the grave dentry */ + if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) { + /* the entry was probably culled when we dropped the parent dir + * lock */ + unlock_rename(cache->graveyard, dir); + _leave(" = 0 [culled?]"); + return 0; + } + + if (!d_can_lookup(cache->graveyard)) { + unlock_rename(cache->graveyard, dir); + erofscache_io_error(cache, "Graveyard no longer a directory"); + return -EIO; + } + + if (trap == rep) { + unlock_rename(cache->graveyard, dir); + erofscache_io_error(cache, "May not make directory loop"); + return -EIO; + } + + if (d_mountpoint(rep)) { + unlock_rename(cache->graveyard, dir); + erofscache_io_error(cache, "Mountpoint in cache"); + return -EIO; + } + + grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer)); + if (IS_ERR(grave)) { + unlock_rename(cache->graveyard, dir); + trace_erofscache_vfs_error(object, d_inode(cache->graveyard), + PTR_ERR(grave), + erofscache_trace_lookup_error); + + if (PTR_ERR(grave) == -ENOMEM) { + _leave(" = -ENOMEM"); + return -ENOMEM; + } + + erofscache_io_error(cache, "Lookup error %ld", PTR_ERR(grave)); + return -EIO; + } + + if (d_is_positive(grave)) { + unlock_rename(cache->graveyard, dir); + dput(grave); + grave = NULL; + cond_resched(); + goto try_again; + } + + if (d_mountpoint(grave)) { + unlock_rename(cache->graveyard, dir); + dput(grave); + erofscache_io_error(cache, "Mountpoint in graveyard"); + return -EIO; + } + + /* target should not be an ancestor of source */ + if (trap == grave) { + unlock_rename(cache->graveyard, dir); + dput(grave); + erofscache_io_error(cache, "May not make directory loop"); + return -EIO; + } + + /* attempt the rename */ + path.mnt = cache->mnt; + path.dentry = dir; + path_to_graveyard.mnt = cache->mnt; + path_to_graveyard.dentry = cache->graveyard; + ret = security_path_rename(&path, rep, &path_to_graveyard, grave, 0); + if (ret < 0) { + erofscache_io_error(cache, "Rename security error %d", ret); + } else { + struct renamedata rd = { + .old_mnt_userns = &init_user_ns, + .old_dir = d_inode(dir), + .old_dentry = rep, + .new_mnt_userns = &init_user_ns, + .new_dir = d_inode(cache->graveyard), + .new_dentry = grave, + }; + trace_erofscache_rename(object, d_inode(rep)->i_ino, why); + ret = erofscache_inject_read_error(); + if (ret == 0) + ret = vfs_rename(&rd); + if (ret != 0) + trace_erofscache_vfs_error(object, d_inode(dir), ret, + erofscache_trace_rename_error); + if (ret != 0 && ret != -ENOMEM) + erofscache_io_error(cache, + "Rename failed with error %d", ret); + } + + __erofscache_unmark_inode_in_use(object, rep); + unlock_rename(cache->graveyard, dir); + dput(grave); + _leave(" = 0"); + return 0; +} + +/* + * Delete a cache file. + */ +int erofscache_delete_object(struct erofscache_object *object, + enum fscache_why_object_killed why) +{ + struct erofscache_volume *volume = object->volume; + struct dentry *dentry = object->file->f_path.dentry; + struct dentry *fan = volume->fanout[(u8)object->cookie->key_hash]; + int ret; + + _enter(",OBJ%x{%pD}", object->debug_id, object->file); + + /* Stop the dentry being negated if it's only pinned by a file struct. */ + dget(dentry); + + inode_lock_nested(d_backing_inode(fan), I_MUTEX_PARENT); + ret = erofscache_unlink(volume->cache, object, fan, dentry, why); + inode_unlock(d_backing_inode(fan)); + dput(dentry); + return ret; +} + +/* + * Open an existing file, checking its attributes and replacing it if it is + * stale. + */ +static bool erofscache_open_file(struct erofscache_object *object, + struct dentry *dentry) +{ + struct erofscache_cache *cache = object->volume->cache; + struct file *file; + struct path path; + int ret; + + _enter("%pd", dentry); + + if (!erofscache_mark_inode_in_use(object, dentry)) + return false; + + /* We need to open a file interface onto a data file now as we can't do + * it on demand because writeback called from do_exit() sees + * current->fs == NULL - which breaks d_path() called from ext4 open. + */ + path.mnt = cache->mnt; + path.dentry = dentry; + file = open_with_fake_path(&path, O_RDONLY | O_LARGEFILE | O_DIRECT, + d_backing_inode(dentry), cache->cache_cred); + if (IS_ERR(file)) { + trace_erofscache_vfs_error(object, d_backing_inode(dentry), + PTR_ERR(file), + erofscache_trace_open_error); + goto error; + } + + if (unlikely(!file->f_op->read_iter)) { + pr_notice("Cache does not support read_iter\n"); + goto error_fput; + } + _debug("file -> %pd positive", dentry); + + ret = erofscache_check_auxdata(object, file); + if (ret < 0) + goto check_failed; + + object->file = file; + + /* Always update the atime on an object we've just looked up (this is + * used to keep track of culling, and atimes are only updated by read, + * write and readdir but not lookup or open). + */ + touch_atime(&file->f_path); + dput(dentry); + return true; + +check_failed: + fscache_cookie_lookup_negative(object->cookie); + erofscache_unmark_inode_in_use(object, file); + if (ret == -ESTALE) { + fput(file); + dput(dentry); + // TODO: Do on-demand load + return false; + } +error_fput: + fput(file); +error: + dput(dentry); + return false; +} + +/* + * walk from the parent object to the child object through the backing + * filesystem, creating directories as we go + */ +bool erofscache_look_up_object(struct erofscache_object *object) +{ + struct erofscache_volume *volume = object->volume; + struct dentry *dentry, *fan = volume->fanout[(u8)object->cookie->key_hash]; + int ret; + + _enter("OBJ%x,%s,", object->debug_id, object->d_name); + + /* Look up path "cache/vol/fanout/file". */ + ret = erofscache_inject_read_error(); + if (ret == 0) + dentry = lookup_positive_unlocked(object->d_name, fan, + object->d_name_len); + else + dentry = ERR_PTR(ret); + trace_erofscache_lookup(object, fan, dentry); + if (IS_ERR(dentry)) { + if (dentry == ERR_PTR(-ENOENT)) + goto new_file; + if (dentry == ERR_PTR(-EIO)) + erofscache_io_error_obj(object, "Lookup failed"); + return false; + } + + if (!d_is_reg(dentry)) { + pr_err("%pd is not a file\n", dentry); + inode_lock_nested(d_inode(fan), I_MUTEX_PARENT); + ret = erofscache_bury_object(volume->cache, object, fan, dentry, + FSCACHE_OBJECT_IS_WEIRD); + dput(dentry); + if (ret < 0) + return false; + goto new_file; + } + + if (!erofscache_open_file(object, dentry)) + return false; + + _leave(" = t [%lu]", file_inode(object->file)->i_ino); + return true; + +new_file: + fscache_cookie_lookup_negative(object->cookie); + return false; // TODO: Trigger on-demand file creation +} + +/* + * Look up an inode to be checked or culled. Return -EBUSY if the inode is + * marked in use. + */ +static struct dentry *erofscache_lookup_for_cull(struct erofscache_cache *cache, + struct dentry *dir, + char *filename) +{ + struct dentry *victim; + int ret = -ENOENT; + + inode_lock_nested(d_inode(dir), I_MUTEX_PARENT); + + victim = lookup_one_len(filename, dir, strlen(filename)); + if (IS_ERR(victim)) + goto lookup_error; + if (d_is_negative(victim)) + goto lookup_put; + if (d_inode(victim)->i_flags & S_KERNEL_FILE) + goto lookup_busy; + return victim; + +lookup_busy: + ret = -EBUSY; +lookup_put: + inode_unlock(d_inode(dir)); + dput(victim); + return ERR_PTR(ret); + +lookup_error: + inode_unlock(d_inode(dir)); + ret = PTR_ERR(victim); + if (ret == -ENOENT) + return ERR_PTR(-ESTALE); /* Probably got retired by the netfs */ + + if (ret == -EIO) { + erofscache_io_error(cache, "Lookup failed"); + } else if (ret != -ENOMEM) { + pr_err("Internal error: %d\n", ret); + ret = -EIO; + } + + return ERR_PTR(ret); +} + +/* + * Cull an object if it's not in use + * - called only by cache manager daemon + */ +int erofscache_cull(struct erofscache_cache *cache, struct dentry *dir, + char *filename) +{ + struct dentry *victim; + struct inode *inode; + int ret; + + _enter(",%pd/,%s", dir, filename); + + victim = erofscache_lookup_for_cull(cache, dir, filename); + if (IS_ERR(victim)) + return PTR_ERR(victim); + + /* check to see if someone is using this object */ + inode = d_inode(victim); + inode_lock(inode); + if (inode->i_flags & S_KERNEL_FILE) { + ret = -EBUSY; + } else { + /* Stop the cache from picking it back up */ + inode->i_flags |= S_KERNEL_FILE; + ret = 0; + } + inode_unlock(inode); + if (ret < 0) + goto error_unlock; + + ret = erofscache_bury_object(cache, NULL, dir, victim, + FSCACHE_OBJECT_WAS_CULLED); + if (ret < 0) + goto error; + + fscache_count_culled(); + dput(victim); + _leave(" = 0"); + return 0; + +error_unlock: + inode_unlock(d_inode(dir)); +error: + dput(victim); + if (ret == -ENOENT) + return -ESTALE; /* Probably got retired by the netfs */ + + if (ret != -ENOMEM) { + pr_err("Internal error: %d\n", ret); + ret = -EIO; + } + + _leave(" = %d", ret); + return ret; +} + +/* + * Find out if an object is in use or not + * - called only by cache manager daemon + * - returns -EBUSY or 0 to indicate whether an object is in use or not + */ +int erofscache_check_in_use(struct erofscache_cache *cache, struct dentry *dir, + char *filename) +{ + struct dentry *victim; + int ret = 0; + + victim = erofscache_lookup_for_cull(cache, dir, filename); + if (IS_ERR(victim)) + return PTR_ERR(victim); + + inode_unlock(d_inode(dir)); + dput(victim); + return ret; +} diff --git a/fs/erofscache/security.c b/fs/erofscache/security.c new file mode 100644 index 000000000000..b642f106e761 --- /dev/null +++ b/fs/erofscache/security.c @@ -0,0 +1,85 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Erofscache security management + * + * Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/fs.h> +#include <linux/cred.h> +#include "internal.h" + +/* + * determine the security context within which we access the cache from within + * the kernel + */ +int erofscache_get_security_ID(struct erofscache_cache *cache) +{ + struct cred *new; + int ret; + + _enter("{%s}", cache->secctx); + + new = prepare_kernel_cred(current); + if (!new) { + ret = -ENOMEM; + goto error; + } + + if (cache->secctx) { + ret = set_security_override_from_ctx(new, cache->secctx); + if (ret < 0) { + put_cred(new); + pr_err("Security denies permission to nominate security context: error %d\n", + ret); + goto error; + } + } + + cache->cache_cred = new; + ret = 0; +error: + _leave(" = %d", ret); + return ret; +} + +/* + * check the security details of the on-disk cache + * - must be called with security override in force + * - must return with a security override in force - even in the case of an + * error + */ +int erofscache_determine_cache_security(struct erofscache_cache *cache, + struct dentry *root, + const struct cred **_saved_cred) +{ + struct cred *new; + int ret; + + _enter(""); + + /* duplicate the cache creds for COW (the override is currently in + * force, so we can use prepare_creds() to do this) */ + new = prepare_creds(); + if (!new) + return -ENOMEM; + + erofscache_end_secure(cache, *_saved_cred); + + /* use the cache root dir's security context as the basis with + * which create files */ + ret = set_create_files_as(new, d_backing_inode(root)); + if (ret < 0) { + abort_creds(new); + erofscache_begin_secure(cache, _saved_cred); + _leave(" = %d [cfa]", ret); + return ret; + } + + put_cred(cache->cache_cred); + cache->cache_cred = new; + + erofscache_begin_secure(cache, _saved_cred); + _leave(" = %d", ret); + return ret; +} diff --git a/fs/erofscache/volume.c b/fs/erofscache/volume.c new file mode 100644 index 000000000000..8c18281b02fe --- /dev/null +++ b/fs/erofscache/volume.c @@ -0,0 +1,129 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Volume handling. + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/fs.h> +#include <linux/slab.h> +#include "internal.h" +#include <trace/events/fscache.h> + +/* + * Allocate and set up a volume representation. We make sure all the fanout + * directories are created and pinned. + */ +void erofscache_acquire_volume(struct fscache_volume *vcookie) +{ + struct erofscache_volume *volume; + struct erofscache_cache *cache = vcookie->cache->cache_priv; + const struct cred *saved_cred; + struct dentry *vdentry, *fan; + size_t len; + char *name; + int ret, n_accesses, i; + + _enter(""); + + volume = kzalloc(sizeof(struct erofscache_volume), GFP_KERNEL); + if (!volume) + return; + volume->vcookie = vcookie; + volume->cache = cache; + INIT_LIST_HEAD(&volume->cache_link); + + erofscache_begin_secure(cache, &saved_cred); + + len = vcookie->key[0]; + name = kmalloc(len + 3, GFP_NOFS); + if (!name) + goto error_vol; + name[0] = 'I'; + memcpy(name + 1, vcookie->key + 1, len); + name[len + 1] = 0; + + vdentry = erofscache_get_directory(cache, cache->store, name); + if (IS_ERR(vdentry)) + goto error_name; + volume->dentry = vdentry; + + ret = erofscache_check_volume_xattr(volume); + if (ret < 0) { + if (ret != -ESTALE) + goto error_dir; + inode_lock_nested(d_inode(cache->store), I_MUTEX_PARENT); + erofscache_bury_object(cache, NULL, cache->store, vdentry, + FSCACHE_VOLUME_IS_WEIRD); + goto error_dir; + } + + for (i = 0; i < 256; i++) { + sprintf(name, "@%02x", i); + fan = erofscache_get_directory(cache, vdentry, name); + if (IS_ERR(fan)) + goto error_fan; + volume->fanout[i] = fan; + } + + erofscache_end_secure(cache, saved_cred); + + vcookie->cache_priv = volume; + n_accesses = atomic_inc_return(&vcookie->n_accesses); /* Stop wakeups on dec-to-0 */ + trace_fscache_access_volume(vcookie->debug_id, 0, + refcount_read(&vcookie->ref), + n_accesses, fscache_access_cache_pin); + + spin_lock(&cache->object_list_lock); + list_add(&volume->cache_link, &volume->cache->volumes); + spin_unlock(&cache->object_list_lock); + + kfree(name); + return; + +error_fan: + for (i = 0; i < 256; i++) + erofscache_put_directory(volume->fanout[i]); +error_dir: + erofscache_put_directory(volume->dentry); +error_name: + kfree(name); +error_vol: + kfree(volume); + erofscache_end_secure(cache, saved_cred); +} + +/* + * Release a volume representation. + */ +static void __erofscache_free_volume(struct erofscache_volume *volume) +{ + int i; + + _enter(""); + + volume->vcookie->cache_priv = NULL; + + for (i = 0; i < 256; i++) + erofscache_put_directory(volume->fanout[i]); + erofscache_put_directory(volume->dentry); + kfree(volume); +} + +void erofscache_free_volume(struct fscache_volume *vcookie) +{ + struct erofscache_volume *volume = vcookie->cache_priv; + + if (volume) { + spin_lock(&volume->cache->object_list_lock); + list_del_init(&volume->cache_link); + spin_unlock(&volume->cache->object_list_lock); + __erofscache_free_volume(volume); + } +} + +void erofscache_withdraw_volume(struct erofscache_volume *volume) +{ + fscache_withdraw_volume(volume->vcookie); + __erofscache_free_volume(volume); +} diff --git a/fs/erofscache/xattr.c b/fs/erofscache/xattr.c new file mode 100644 index 000000000000..1f2408131c9e --- /dev/null +++ b/fs/erofscache/xattr.c @@ -0,0 +1,146 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Erofscache extended attribute management + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include <linux/module.h> +#include <linux/sched.h> +#include <linux/file.h> +#include <linux/fs.h> +#include <linux/fsnotify.h> +#include <linux/quotaops.h> +#include <linux/xattr.h> +#include <linux/slab.h> +#include "internal.h" + +#define EROFSCACHE_COOKIE_TYPE_DATA 1 + +struct erofscache_xattr { + __be64 object_size; /* Actual size of the object */ + __u8 type; /* Type of object */ + __u8 data[]; /* netfs coherency data */ +} __packed; + +static const char erofscache_xattr_cache[] = + XATTR_USER_PREFIX "Erofscache.cache"; + +/* + * check the consistency between the backing cache and the FS-Cache cookie + */ +int erofscache_check_auxdata(struct erofscache_object *object, struct file *file) +{ + struct erofscache_xattr *buf; + struct dentry *dentry = file->f_path.dentry; + unsigned int len = object->cookie->aux_len, tlen; + const void *p = fscache_get_aux(object->cookie); + enum erofscache_coherency_trace why; + ssize_t xlen; + int ret = -ESTALE; + + tlen = sizeof(struct erofscache_xattr) + len; + buf = kmalloc(tlen, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + xlen = erofscache_inject_read_error(); + if (xlen == 0) + xlen = vfs_getxattr(&init_user_ns, dentry, erofscache_xattr_cache, buf, tlen); + if (xlen != tlen) { + if (xlen < 0) + trace_erofscache_vfs_error(object, file_inode(file), xlen, + erofscache_trace_getxattr_error); + if (xlen == -EIO) + erofscache_io_error_obj( + object, + "Failed to read aux with error %zd", xlen); + why = erofscache_coherency_check_xattr; + } else if (buf->type != EROFSCACHE_COOKIE_TYPE_DATA) { + why = erofscache_coherency_check_type; + } else if (memcmp(buf->data, p, len) != 0) { + why = erofscache_coherency_check_aux; + } else if (be64_to_cpu(buf->object_size) != object->cookie->object_size) { + why = erofscache_coherency_check_objsize; + } else { + why = erofscache_coherency_check_ok; + ret = 0; + } + + trace_erofscache_coherency(object, file_inode(file)->i_ino, why); + kfree(buf); + return ret; +} + +/* + * remove the object's xattr to mark it stale + */ +int erofscache_remove_object_xattr(struct erofscache_cache *cache, + struct erofscache_object *object, + struct dentry *dentry) +{ + int ret; + + ret = erofscache_inject_remove_error(); + if (ret == 0) + ret = vfs_removexattr(&init_user_ns, dentry, erofscache_xattr_cache); + if (ret < 0) { + trace_erofscache_vfs_error(object, d_inode(dentry), ret, + erofscache_trace_remxattr_error); + if (ret == -ENOENT || ret == -ENODATA) + ret = 0; + else if (ret != -ENOMEM) + erofscache_io_error(cache, + "Can't remove xattr from %lu" + " (error %d)", + d_backing_inode(dentry)->i_ino, -ret); + } + + _leave(" = %d", ret); + return ret; +} + +/* + * Check the consistency between the backing cache and the volume cookie. + */ +int erofscache_check_volume_xattr(struct erofscache_volume *volume) +{ + struct erofscache_xattr *buf; + struct dentry *dentry = volume->dentry; + unsigned int len = volume->vcookie->coherency_len; + const void *p = volume->vcookie->coherency; + enum erofscache_coherency_trace why; + ssize_t xlen; + int ret = -ESTALE; + + _enter(""); + + buf = kmalloc(len, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + xlen = erofscache_inject_read_error(); + if (xlen == 0) + xlen = vfs_getxattr(&init_user_ns, dentry, erofscache_xattr_cache, buf, len); + if (xlen != len) { + if (xlen < 0) { + trace_erofscache_vfs_error(NULL, d_inode(dentry), xlen, + erofscache_trace_getxattr_error); + if (xlen == -EIO) + erofscache_io_error( + volume->cache, + "Failed to read xattr with error %zd", xlen); + } + why = erofscache_coherency_vol_check_xattr; + } else if (memcmp(buf->data, p, len) != 0) { + why = erofscache_coherency_vol_check_cmp; + } else { + why = erofscache_coherency_vol_check_ok; + ret = 0; + } + + trace_erofscache_vol_coherency(volume, d_inode(dentry)->i_ino, why); + kfree(buf); + _leave(" = %d", ret); + return ret; +} diff --git a/include/trace/events/erofscache.h b/include/trace/events/erofscache.h new file mode 100644 index 000000000000..96974fd097f0 --- /dev/null +++ b/include/trace/events/erofscache.h @@ -0,0 +1,515 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* Erofscache tracepoints + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM erofscache + +#if !defined(_TRACE_EROFSCACHE_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_EROFSCACHE_H + +#include <linux/tracepoint.h> + +/* + * Define enums for tracing information. + */ +#ifndef __EROFSCACHE_DECLARE_TRACE_ENUMS_ONCE_ONLY +#define __EROFSCACHE_DECLARE_TRACE_ENUMS_ONCE_ONLY + +enum erofscache_obj_ref_trace { + erofscache_obj_get_ioreq, + erofscache_obj_new, + erofscache_obj_put_alloc_fail, + erofscache_obj_put_detach, + erofscache_obj_put_ioreq, + erofscache_obj_see_clean_commit, + erofscache_obj_see_clean_delete, + erofscache_obj_see_clean_drop_tmp, + erofscache_obj_see_lookup_cookie, + erofscache_obj_see_lookup_failed, + erofscache_obj_see_withdraw_cookie, + erofscache_obj_see_withdrawal, +}; + +enum fscache_why_object_killed { + FSCACHE_OBJECT_IS_STALE, + FSCACHE_OBJECT_IS_WEIRD, + FSCACHE_OBJECT_INVALIDATED, + FSCACHE_OBJECT_NO_SPACE, + FSCACHE_OBJECT_WAS_RETIRED, + FSCACHE_OBJECT_WAS_CULLED, + FSCACHE_VOLUME_IS_WEIRD, +}; + +enum erofscache_coherency_trace { + erofscache_coherency_check_aux, + erofscache_coherency_check_content, + erofscache_coherency_check_dirty, + erofscache_coherency_check_len, + erofscache_coherency_check_objsize, + erofscache_coherency_check_ok, + erofscache_coherency_check_type, + erofscache_coherency_check_xattr, + erofscache_coherency_vol_check_cmp, + erofscache_coherency_vol_check_ok, + erofscache_coherency_vol_check_xattr, +}; + +enum erofscache_prepare_read_trace { + erofscache_trace_read_after_eof, + erofscache_trace_read_found_hole, + erofscache_trace_read_found_part, + erofscache_trace_read_have_data, + erofscache_trace_read_no_data, + erofscache_trace_read_no_file, + erofscache_trace_read_seek_error, + erofscache_trace_read_seek_nxio, +}; + +enum erofscache_error_trace { + erofscache_trace_getxattr_error, + erofscache_trace_link_error, + erofscache_trace_lookup_error, + erofscache_trace_open_error, + erofscache_trace_read_error, + erofscache_trace_remxattr_error, + erofscache_trace_rename_error, + erofscache_trace_seek_error, + erofscache_trace_unlink_error, +}; + +#endif + +/* + * Define enum -> string mappings for display. + */ +#define erofscache_obj_kill_traces \ + EM(FSCACHE_OBJECT_IS_STALE, "stale") \ + EM(FSCACHE_OBJECT_IS_WEIRD, "weird") \ + EM(FSCACHE_OBJECT_INVALIDATED, "inval") \ + EM(FSCACHE_OBJECT_NO_SPACE, "no_space") \ + EM(FSCACHE_OBJECT_WAS_RETIRED, "was_retired") \ + EM(FSCACHE_OBJECT_WAS_CULLED, "was_culled") \ + E_(FSCACHE_VOLUME_IS_WEIRD, "volume_weird") + +#define erofscache_obj_ref_traces \ + EM(erofscache_obj_get_ioreq, "GET ioreq") \ + EM(erofscache_obj_new, "NEW obj") \ + EM(erofscache_obj_put_alloc_fail, "PUT alloc_fail") \ + EM(erofscache_obj_put_detach, "PUT detach") \ + EM(erofscache_obj_put_ioreq, "PUT ioreq") \ + EM(erofscache_obj_see_clean_commit, "SEE clean_commit") \ + EM(erofscache_obj_see_clean_delete, "SEE clean_delete") \ + EM(erofscache_obj_see_clean_drop_tmp, "SEE clean_drop_tmp") \ + EM(erofscache_obj_see_lookup_cookie, "SEE lookup_cookie") \ + EM(erofscache_obj_see_lookup_failed, "SEE lookup_failed") \ + EM(erofscache_obj_see_withdraw_cookie, "SEE withdraw_cookie") \ + E_(erofscache_obj_see_withdrawal, "SEE withdrawal") + +#define erofscache_coherency_traces \ + EM(erofscache_coherency_check_aux, "BAD aux ") \ + EM(erofscache_coherency_check_content, "BAD cont") \ + EM(erofscache_coherency_check_dirty, "BAD dirt") \ + EM(erofscache_coherency_check_len, "BAD len ") \ + EM(erofscache_coherency_check_objsize, "BAD osiz") \ + EM(erofscache_coherency_check_ok, "OK ") \ + EM(erofscache_coherency_check_type, "BAD type") \ + EM(erofscache_coherency_check_xattr, "BAD xatt") \ + EM(erofscache_coherency_vol_check_cmp, "VOL BAD cmp ") \ + EM(erofscache_coherency_vol_check_ok, "VOL OK ") \ + E_(erofscache_coherency_vol_check_xattr,"VOL BAD xatt") + +#define erofscache_prepare_read_traces \ + EM(erofscache_trace_read_after_eof, "after-eof ") \ + EM(erofscache_trace_read_found_hole, "found-hole") \ + EM(erofscache_trace_read_found_part, "found-part") \ + EM(erofscache_trace_read_have_data, "have-data ") \ + EM(erofscache_trace_read_no_data, "no-data ") \ + EM(erofscache_trace_read_no_file, "no-file ") \ + EM(erofscache_trace_read_seek_error, "seek-error") \ + E_(erofscache_trace_read_seek_nxio, "seek-enxio") + +#define erofscache_error_traces \ + EM(erofscache_trace_getxattr_error, "getxattr") \ + EM(erofscache_trace_lookup_error, "lookup") \ + EM(erofscache_trace_open_error, "open") \ + EM(erofscache_trace_read_error, "read") \ + EM(erofscache_trace_remxattr_error, "remxattr") \ + EM(erofscache_trace_rename_error, "rename") \ + EM(erofscache_trace_seek_error, "seek") \ + E_(erofscache_trace_unlink_error, "unlink") + + +/* + * Export enum symbols via userspace. + */ +#undef EM +#undef E_ +#define EM(a, b) TRACE_DEFINE_ENUM(a); +#define E_(a, b) TRACE_DEFINE_ENUM(a); + +erofscache_obj_kill_traces; +erofscache_obj_ref_traces; +erofscache_coherency_traces; +erofscache_prepare_read_traces; +erofscache_error_traces; + +/* + * Now redefine the EM() and E_() macros to map the enums to the strings that + * will be printed in the output. + */ +#undef EM +#undef E_ +#define EM(a, b) { a, b }, +#define E_(a, b) { a, b } + + +TRACE_EVENT(erofscache_ref, + TP_PROTO(unsigned int object_debug_id, + unsigned int cookie_debug_id, + int usage, + enum erofscache_obj_ref_trace why), + + TP_ARGS(object_debug_id, cookie_debug_id, usage, why), + + /* Note that obj may be NULL */ + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(unsigned int, cookie ) + __field(enum erofscache_obj_ref_trace, why ) + __field(int, usage ) + ), + + TP_fast_assign( + __entry->obj = object_debug_id; + __entry->cookie = cookie_debug_id; + __entry->usage = usage; + __entry->why = why; + ), + + TP_printk("c=%08x o=%08x u=%d %s", + __entry->cookie, __entry->obj, __entry->usage, + __print_symbolic(__entry->why, erofscache_obj_ref_traces)) + ); + +TRACE_EVENT(erofscache_lookup, + TP_PROTO(struct erofscache_object *obj, + struct dentry *dir, + struct dentry *de), + + TP_ARGS(obj, dir, de), + + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(short, error ) + __field(unsigned long, dino ) + __field(unsigned long, ino ) + ), + + TP_fast_assign( + __entry->obj = obj ? obj->debug_id : 0; + __entry->dino = d_backing_inode(dir)->i_ino; + __entry->ino = (!IS_ERR(de) && d_backing_inode(de) ? + d_backing_inode(de)->i_ino : 0); + __entry->error = IS_ERR(de) ? PTR_ERR(de) : 0; + ), + + TP_printk("o=%08x dB=%lx B=%lx e=%d", + __entry->obj, __entry->dino, __entry->ino, __entry->error) + ); + +TRACE_EVENT(erofscache_unlink, + TP_PROTO(struct erofscache_object *obj, + ino_t ino, + enum fscache_why_object_killed why), + + TP_ARGS(obj, ino, why), + + /* Note that obj may be NULL */ + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(unsigned int, ino ) + __field(enum fscache_why_object_killed, why ) + ), + + TP_fast_assign( + __entry->obj = obj ? obj->debug_id : UINT_MAX; + __entry->ino = ino; + __entry->why = why; + ), + + TP_printk("o=%08x B=%x w=%s", + __entry->obj, __entry->ino, + __print_symbolic(__entry->why, erofscache_obj_kill_traces)) + ); + +TRACE_EVENT(erofscache_rename, + TP_PROTO(struct erofscache_object *obj, + ino_t ino, + enum fscache_why_object_killed why), + + TP_ARGS(obj, ino, why), + + /* Note that obj may be NULL */ + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(unsigned int, ino ) + __field(enum fscache_why_object_killed, why ) + ), + + TP_fast_assign( + __entry->obj = obj ? obj->debug_id : UINT_MAX; + __entry->ino = ino; + __entry->why = why; + ), + + TP_printk("o=%08x B=%x w=%s", + __entry->obj, __entry->ino, + __print_symbolic(__entry->why, erofscache_obj_kill_traces)) + ); + +TRACE_EVENT(erofscache_coherency, + TP_PROTO(struct erofscache_object *obj, + ino_t ino, + enum erofscache_coherency_trace why), + + TP_ARGS(obj, ino, why), + + /* Note that obj may be NULL */ + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(enum erofscache_coherency_trace, why ) + __field(u64, ino ) + ), + + TP_fast_assign( + __entry->obj = obj->debug_id; + __entry->why = why; + __entry->ino = ino; + ), + + TP_printk("o=%08x %s B=%llx", + __entry->obj, + __print_symbolic(__entry->why, erofscache_coherency_traces), + __entry->ino) + ); + +TRACE_EVENT(erofscache_vol_coherency, + TP_PROTO(struct erofscache_volume *volume, + ino_t ino, + enum erofscache_coherency_trace why), + + TP_ARGS(volume, ino, why), + + /* Note that obj may be NULL */ + TP_STRUCT__entry( + __field(unsigned int, vol ) + __field(enum erofscache_coherency_trace, why ) + __field(u64, ino ) + ), + + TP_fast_assign( + __entry->vol = volume->vcookie->debug_id; + __entry->why = why; + __entry->ino = ino; + ), + + TP_printk("V=%08x %s B=%llx", + __entry->vol, + __print_symbolic(__entry->why, erofscache_coherency_traces), + __entry->ino) + ); + +TRACE_EVENT(erofscache_prep_read, + TP_PROTO(struct netfs_read_subrequest *sreq, + enum netfs_read_source source, + enum erofscache_prepare_read_trace why, + ino_t cache_inode), + + TP_ARGS(sreq, source, why, cache_inode), + + TP_STRUCT__entry( + __field(unsigned int, rreq ) + __field(unsigned short, index ) + __field(unsigned short, flags ) + __field(enum netfs_read_source, source ) + __field(enum erofscache_prepare_read_trace, why ) + __field(size_t, len ) + __field(loff_t, start ) + __field(unsigned int, netfs_inode ) + __field(unsigned int, cache_inode ) + ), + + TP_fast_assign( + __entry->rreq = sreq->rreq->debug_id; + __entry->index = sreq->debug_index; + __entry->flags = sreq->flags; + __entry->source = source; + __entry->why = why; + __entry->len = sreq->len; + __entry->start = sreq->start; + __entry->netfs_inode = sreq->rreq->inode->i_ino; + __entry->cache_inode = cache_inode; + ), + + TP_printk("R=%08x[%u] %s %s f=%02x s=%llx %zx ni=%x B=%x", + __entry->rreq, __entry->index, + __print_symbolic(__entry->source, netfs_sreq_sources), + __print_symbolic(__entry->why, erofscache_prepare_read_traces), + __entry->flags, + __entry->start, __entry->len, + __entry->netfs_inode, __entry->cache_inode) + ); + +TRACE_EVENT(erofscache_read, + TP_PROTO(struct erofscache_object *obj, + struct inode *backer, + loff_t start, + size_t len), + + TP_ARGS(obj, backer, start, len), + + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(unsigned int, backer ) + __field(size_t, len ) + __field(loff_t, start ) + ), + + TP_fast_assign( + __entry->obj = obj->debug_id; + __entry->backer = backer->i_ino; + __entry->start = start; + __entry->len = len; + ), + + TP_printk("o=%08x B=%x s=%llx l=%zx", + __entry->obj, + __entry->backer, + __entry->start, + __entry->len) + ); + +TRACE_EVENT(erofscache_mark_active, + TP_PROTO(struct erofscache_object *obj, + struct inode *inode), + + TP_ARGS(obj, inode), + + /* Note that obj may be NULL */ + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(ino_t, inode ) + ), + + TP_fast_assign( + __entry->obj = obj ? obj->debug_id : 0; + __entry->inode = inode->i_ino; + ), + + TP_printk("o=%08x B=%lx", + __entry->obj, __entry->inode) + ); + +TRACE_EVENT(erofscache_mark_failed, + TP_PROTO(struct erofscache_object *obj, + struct inode *inode), + + TP_ARGS(obj, inode), + + /* Note that obj may be NULL */ + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(ino_t, inode ) + ), + + TP_fast_assign( + __entry->obj = obj ? obj->debug_id : 0; + __entry->inode = inode->i_ino; + ), + + TP_printk("o=%08x B=%lx", + __entry->obj, __entry->inode) + ); + +TRACE_EVENT(erofscache_mark_inactive, + TP_PROTO(struct erofscache_object *obj, + struct inode *inode), + + TP_ARGS(obj, inode), + + /* Note that obj may be NULL */ + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(ino_t, inode ) + ), + + TP_fast_assign( + __entry->obj = obj ? obj->debug_id : 0; + __entry->inode = inode->i_ino; + ), + + TP_printk("o=%08x B=%lx", + __entry->obj, __entry->inode) + ); + +TRACE_EVENT(erofscache_vfs_error, + TP_PROTO(struct erofscache_object *obj, struct inode *backer, + int error, enum erofscache_error_trace where), + + TP_ARGS(obj, backer, error, where), + + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(unsigned int, backer ) + __field(enum erofscache_error_trace, where ) + __field(short, error ) + ), + + TP_fast_assign( + __entry->obj = obj ? obj->debug_id : 0; + __entry->backer = backer->i_ino; + __entry->error = error; + __entry->where = where; + ), + + TP_printk("o=%08x B=%x %s e=%d", + __entry->obj, + __entry->backer, + __print_symbolic(__entry->where, erofscache_error_traces), + __entry->error) + ); + +TRACE_EVENT(erofscache_io_error, + TP_PROTO(struct erofscache_object *obj, struct inode *backer, + int error, enum erofscache_error_trace where), + + TP_ARGS(obj, backer, error, where), + + TP_STRUCT__entry( + __field(unsigned int, obj ) + __field(unsigned int, backer ) + __field(enum erofscache_error_trace, where ) + __field(short, error ) + ), + + TP_fast_assign( + __entry->obj = obj ? obj->debug_id : 0; + __entry->backer = backer->i_ino; + __entry->error = error; + __entry->where = where; + ), + + TP_printk("o=%08x B=%x %s e=%d", + __entry->obj, + __entry->backer, + __print_symbolic(__entry->where, erofscache_error_traces), + __entry->error) + ); + +#endif /* _TRACE_EROFSCACHE_H */ + +/* This part must be outside protection */ +#include <trace/define_trace.h>
On 1/26/22 4:27 AM, David Howells wrote: > David Howells <dhowells@redhat.com> wrote: > >> (1) Duplicate the cachefiles backend. You can discard a lot of it, since a >> much of it is concerned with managing local modifications - which you're >> not going to do since you have a R/O filesystem and you're looking at >> importing files into the cache externally to the kernel. > > Take the attached as a start. It's completely untested. I've stripped out > anything to do with writing to the cache, making directories, etc. as that can > probably be delegated to the on-demand creation. You could drive on-demand > creation from the points where it would create files. I've put some "TODO" > comments in there as markers. Thanks for your inspiring work. Some questions below. > > You could also strip out everything to do with invalidation and also make it > just fail if it encounters a file type that it doesn't like or a file that is > not correctly labelled for a coherency attribute. > > Also, since you aren't intending to write anything or create new files here, > there's no need to do the space checking - so I've got rid of all that too. > > I've also made it open the backing files read only and got rid of the trimming > to I/O blocksize for DIO purposes. The userspace side can take care of that - > and, besides, you want to have multiple files within a backing file, right? > > You might want to stop it from marking cache *files* in use (but only mark > directories). It doesn't matter so much as you aren't going to get coherency > issues from having multiple writers to the same file. > > You then need to add a file offset member to the erofscache_object struct, set > that when the backing file is looked up and add it to the file position in > erofscache_read(). You also need to look at erofscache_prepare_read(). If > your files are contiguous complete blobs, that can be a lot simpler. To be honest, I'm not sure if I get your points correctly. Do you mean each file in erofs has only one chunk (and thus corresponds to only one backing blob file), so that netfs lib can work well while given the only cookie associated with the netfs file? By the way, let me explain the blob mapping in erofs further. To implement deduplication, one erofs file can be divided into multiple chunks, while these chunks can be distributed over several backing blob files quite randomly (rather than a round-robin style). Each erofs file maintains an on-disk map describing the mapping relationship between chunks and backing blob files. Something like the extent map. Thus there's a multi-to-multi relationship between erofs file and backing blob file. Thus each erofs file can correspond to multiple cookies in this way, i.e. one 'struct netfs_i_context' can correspond to multiple cookies. Besides, the mapping relationship between chunks and backing blob files is totally implemented in upper fs (i.e. erofs), I have no idea how we can "do the blob mapping in the backend" [1]. So I don't think we can use netfs lib **directly** even with this R/O fscache backend implemented. Please correct me if I misunderstand it. [1] https://lore.kernel.org/lkml/Yeeye2AUZITDsdh8@B-P7TQMD6M-0146.local/T/#mfbb2053476760d8fac723c57dad529192a5084c6 Besides, IMHO it may suffer great challenges when implementing a new R/O backend, since there's quite many code duplication. I know it's just a starting version from scratch, but I'm not sure if it's worth it.
On 1/26/22 12:15 AM, David Howells wrote: > Jeffle Xu <jefflexu@linux.alibaba.com> wrote: > >> The following issues still need further discussion. Thanks for your time >> and patience. >> >> 1. I noticed that there's refactoring of netfs library[1], >> ... >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=netfs-lib > > Yes. I'm working towards getting netfslib to do handling writes and dio as > well as reads, along with content crypto/compression, and the idea I'm aiming > towards is that you just point your address_space_ops at netfs directly if > possible - but it's going to require its own context now to manage pending > writes. > > See my netfs-experimental branch for more of that - it's still a work in > progress, though. Got it. > > Btw, you could set rreq->netfs_priv in ->init_rreq() rather than passing it in > to netfs_readpage(). > >> 2. The current implementation will severely conflict with the >> refactoring of netfs library[1][2]. The assumption of 'struct >> netfs_i_context' [2] is that, every file in the upper netfs will >> correspond to only one backing file. While in our scenario, one file in >> erofs can correspond to multiple backing files. That is, the content of >> one file can be divided into multiple chunks, and are distrubuted over >> multiple blob files, i.e. multiple backing files. Currently I have no >> good idea solving this conflic. > > I can think of a couple of options to explore: > > (1) Duplicate the cachefiles backend. You can discard a lot of it, since a > much of it is concerned with managing local modifications - which you're > not going to do since you have a R/O filesystem and you're looking at > importing files into the cache externally to the kernel. > > I would suggest looking to see if you can do the blob mapping in the > backend rather than passing the offset down. Maybe make the cookie index > key hold the index too, e.g. "/path/to/file+offset". Have been discussed in [1]. [1] https://lore.kernel.org/lkml/Yeeye2AUZITDsdh8@B-P7TQMD6M-0146.local/T/#m25b1229f96bf24929fb73746a07e9996e8222ac6 "/path/to/file+offset" ^ Besides, what does the 'offset' mean? > > Btw, do you still need cachefilesd for its culling duties? Yes we still need cache management in this on-demand scenario, in case of backing files exhausting the available blocks. (Though these backing files are prepared by daemon in advance, these files can all be sparse files.) And similarly the actual culling work should be done under protection of S_KERNEL_FILE, so that the culled backing file can't be picked back up. > > (2) Do you actually need to go through netfslib? Might it be easier to call > fscache_read() directly? Have a look at fs/nfs/fscache.c It would be great if we can use fscache_read() directly. > >> Besides there are still two quetions: >> - What's the plan of [1]? When is it planned to be merged? > > Hopefully next merge window, but that's going to depend on a number of things. > >> - It seems that all upper fs using fscache is going to use netfs API, >> while the APIs like fscache_read_or_alloc_page() are deprecated. Is >> that true? > > fscache_read_or_alloc_page() is gone completely. > > You don't have to use the netfs API. You can talk to fscache directly, > doing DIO from the cache to an xarray-class iov_iter constructed from your > inode's pagecache. > > netfslib provides/will provide a number of services, such as multipage > folios, transparent caching, crypto, compression and hiding the existence of > pages/folios from the filesystem as entirely as possible. However, you > already have some of these implemented on top of iomap for the blockdev > interface, it would appear. > Got it. In summary, 1) I prefer option 2, i.e. calling fscache_read() directly, as the one at hand. In this case, the conflict with the netfs lib refactoring can be avoided. Besides, there will be less modification needed to cachefiles/netfs. Patch 1~3 are no longer required, while patch 4~6 are still needed, which mainly introduce the new devnode. 2) Later we can change to option 1, i.e. calling netfs lib and also a potential new R/O backend, if the issues in [1] can be clarified or solved. [1] https://lore.kernel.org/lkml/Yeeye2AUZITDsdh8@B-P7TQMD6M-0146.local/T/#m25b1229f96bf24929fb73746a07e9996e8222ac6
JeffleXu <jefflexu@linux.alibaba.com> wrote: > "/path/to/file+offset" > ^ > > Besides, what does the 'offset' mean? Assuming you're storing multiple erofs files within the same backend file, you need to tell the the cache backend how to find the data. Assuming the erofs data is arranged such that each erofs file is a single contiguous region, then you need a pathname and a file offset to find one of them. David
On 1/26/22 4:51 PM, David Howells wrote: > JeffleXu <jefflexu@linux.alibaba.com> wrote: > >> "/path/to/file+offset" >> ^ >> >> Besides, what does the 'offset' mean? > > Assuming you're storing multiple erofs files within the same backend file, you > need to tell the the cache backend how to find the data. Assuming the erofs > data is arranged such that each erofs file is a single contiguous region, then > you need a pathname and a file offset to find one of them. > Alright. In fact one erofs file can contain multiple chunks, which can correspond to different backing blob files. Thus currently I will use fscache_read() directly, to push this feature forward. Thanks a lot.