| Message ID | 20250118-vfs-netfs-ba988c7b2167@brauner (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [GIT,PULL] vfs netfs | expand |
diff --cc fs/netfs/direct_write.c index f9421f3e6d37,eded8afaa60b..000000000000 --- a/fs/netfs/direct_write.c diff --cc fs/netfs/read_retry.c index 16b676c68dcd,bf6f26525b0d..000000000000 --- a/fs/netfs/read_retry.c
Hey Linus, /* Summary */ This contains read performance improvements and support for monolithic single-blob objects that have to be read/written as such (e.g. AFS directory contents). The implementation of the two parts is interwoven as each makes the other possible. - Read performance improvements The read performance improvements are intended to speed up some loss of performance detected in cifs and to a lesser extend in afs. The problem is that we queue too many work items during the collection of read results: each individual subrequest is collected by its own work item, and then they have to interact with each other when a series of subrequests don't exactly align with the pattern of folios that are being read by the overall request. Whilst the processing of the pages covered by individual subrequests as they complete potentially allows folios to be woken in parallel and with minimum delay, it can shuffle wakeups for sequential reads out of order - and that is the most common I/O pattern. The final assessment and cleanup of an operation is then held up until the last I/O completes - and for a synchronous sequential operation, this means the bouncing around of work items just adds latency. Two changes have been made to make this work: (1) All collection is now done in a single "work item" that works progressively through the subrequests as they complete (and also dispatches retries as necessary). (2) For readahead and AIO, this work item be done on a workqueue and can run in parallel with the ultimate consumer of the data; for synchronous direct or unbuffered reads, the collection is run in the application thread and not offloaded. Functions such as smb2_readv_callback() then just tell netfslib that the subrequest has terminated; netfslib does a minimal bit of processing on the spot - stat counting and tracing mostly - and then queues/wakes up the worker. This simplifies the logic as the collector just walks sequentially through the subrequests as they complete and walks through the folios, if buffered, unlocking them as it goes. It also keeps to a minimum the amount of latency injected into the filesystem's low-level I/O handling The way netfs supports filesystems using the deprecated PG_private_2 flag is changed: folios are flagged and added to a write request as they complete and that takes care of scheduling the writes to the cache. The originating read request can then just unlock the pages whatever happens. - Single-blob object support Single-blob objects are files for which the content of the file must be read from or written to the server in a single operation because reading them in parts may yield inconsistent results. AFS directories are an example of this as there exists the possibility that the contents are generated on the fly and would differ between reads or might change due to third party interference. Such objects will be written to and retrieved from the cache if one is present, though we allow/may need to propose multiple subrequests to do so. The important part is that read from/write to the *server* is monolithic. Single blob reading is, for the moment, fully synchronous and does result collection in the application thread and, also for the moment, the API is supplied the buffer in the form of a folio_queue chain rather than using the pagecache. - Related afs changes This series makes a number of changes to the kafs filesystem, primarily in the area of directory handling: - AFS's FetchData RPC reply processing is made partially asynchronous which allows the netfs_io_request's outstanding operation counter to be removed as part of reducing the collection to a single work item. - Directory and symlink reading are plumbed through netfslib using the single-blob object API and are now cacheable with fscache. This also allows the afs_read struct to be eliminated and netfs_io_subrequest to be used directly instead. - Directory and symlink content are now stored in a folio_queue buffer rather than in the pagecache. This means we don't require the RCU read lock and xarray iteration to access it, and folios won't randomly disappear under us because the VM wants them back. - The vnode operation lock is changed from a mutex struct to a private lock implementation. The problem is that the lock now needs to be dropped in a separate thread and mutexes don't permit that. - When a new directory or symlink is created, we now initialise it locally and mark it valid rather than downloading it (we know what it's likely to look like). - We now use the in-directory hashtable to reduce the number of entries we need to scan when doing a lookup. The edit routines have to maintain the hash chains. - Cancellation (e.g. by signal) of an async call after the rxrpc_call has been set up is now offloaded to the worker thread as there will be a notification from rxrpc upon completion. This avoids a double cleanup. - A "rolling buffer" implementation is created to abstract out the two separate folio_queue chaining implementations I had (one for read and one for write). - Functions are provided to create/extend a buffer in a folio_queue chain and tear it down again. This is used to handle AFS directories, but could also be used to create bounce buffers for content crypto and transport crypto. - The was_async argument is dropped from netfs_read_subreq_terminated(). Instead we wake the read collection work item by either queuing it or waking up the app thread. - We don't need to use BH-excluding locks when communicating between the issuing thread and the collection thread as neither of them now run in BH context. - Also included are a number of new tracepoints; a split of the netfslib write collection code to put retrying into its own file (it gets more complicated with content encryption). - There are also some minor fixes AFS included, including fixing the AFS directory format struct layout, reducing some directory over-invalidation and making afs_mkdir() translate EEXIST to ENOTEMPY (which is not available on all systems the servers support). - Finally, there's a patch to try and detect entry into the folio unlock function with no folio_queue structs in the buffer (which isn't allowed in the cases that can get there). This is a debugging patch, but should be minimal overhead. /* Testing */ gcc version 14.2.0 (Debian 14.2.0-6) Debian clang version 16.0.6 (27+b1) No build failures or warnings were observed. /* Conflicts */ Merge conflicts with mainline ============================= There's a merge conflict that can be resolved as follows: +++ b/fs/netfs/direct_write.c @@@ -67,8 -67,8 +67,8 @@@ ssize_t netfs_unbuffered_write_iter_loc * allocate a sufficiently large bvec array and may shorten the * request. */ - if (async || user_backed_iter(iter)) { + if (user_backed_iter(iter)) { - n = netfs_extract_user_iter(iter, len, &wreq->iter, 0); + n = netfs_extract_user_iter(iter, len, &wreq->buffer.iter, 0); if (n < 0) { ret = n; goto out; @@@ -77,15 -77,8 +77,13 @@@ wreq->direct_bv_count = n; wreq->direct_bv_unpin = iov_iter_extract_will_pin(iter); } else { + /* If this is a kernel-generated async DIO request, + * assume that any resources the iterator points to + * (eg. a bio_vec array) will persist till the end of + * the op. + */ - wreq->iter = *iter; + wreq->buffer.iter = *iter; } - - wreq->io_iter = wreq->iter; } __set_bit(NETFS_RREQ_USE_IO_ITER, &wreq->flags); +++ b/fs/netfs/read_retry.c @@@ -142,25 -125,19 +125,20 @@@ static void netfs_retry_read_subrequest __clear_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags); subreq->retry_count++; - spin_lock_bh(&rreq->lock); - list_add_tail(&subreq->rreq_link, &rreq->subrequests); - subreq->prev_donated += rreq->prev_donated; - rreq->prev_donated = 0; trace_netfs_sreq(subreq, netfs_sreq_trace_retry); - spin_unlock_bh(&rreq->lock); - - BUG_ON(!len); /* Renegotiate max_len (rsize) */ + stream->sreq_max_len = subreq->len; - if (rreq->netfs_ops->prepare_read(subreq) < 0) { + if (rreq->netfs_ops->prepare_read && + rreq->netfs_ops->prepare_read(subreq) < 0) { trace_netfs_sreq(subreq, netfs_sreq_trace_reprep_failed); __set_bit(NETFS_SREQ_FAILED, &subreq->flags); + goto abandon; } - part = umin(len, stream0->sreq_max_len); - if (unlikely(rreq->io_streams[0].sreq_max_segs)) - part = netfs_limit_iter(&source, 0, part, stream0->sreq_max_segs); + part = umin(len, stream->sreq_max_len); + if (unlikely(stream->sreq_max_segs)) + part = netfs_limit_iter(&source, 0, part, stream->sreq_max_segs); subreq->len = subreq->transferred + part; subreq->io_iter = source; iov_iter_truncate(&subreq->io_iter, part); Merge conflicts with other trees ================================ No known conflicts. The following changes since commit 5fe85a5c513344161cde33b79f8badc81b8aa8d3: Merge patch series "netfs, ceph, nfs, cachefiles: Miscellaneous fixes/changes" (2024-12-20 22:08:16 +0100) are available in the Git repository at: git@gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs tags/vfs-6.14-rc1.netfs for you to fetch changes up to 7a47db23a9f003614e15c687d2a5425c175a9ca8: Merge patch series "netfs: Read performance improvements and "single-blob" support" (2024-12-20 22:34:18 +0100) Please consider pulling these changes from the signed vfs-6.14-rc1.netfs tag. Thanks! Christian ---------------------------------------------------------------- vfs-6.14-rc1.netfs ---------------------------------------------------------------- Christian Brauner (1): Merge patch series "netfs: Read performance improvements and "single-blob" support" David Howells (31): netfs: Clean up some whitespace in trace header cachefiles: Clean up some whitespace in trace header netfs: Use a folio_queue allocation and free functions netfs: Add a tracepoint to log the lifespan of folio_queue structs netfs: Abstract out a rolling folio buffer implementation netfs: Make netfs_advance_write() return size_t netfs: Split retry code out of fs/netfs/write_collect.c netfs: Drop the error arg from netfs_read_subreq_terminated() netfs: Drop the was_async arg from netfs_read_subreq_terminated() netfs: Don't use bh spinlock afs: Don't use mutex for I/O operation lock afs: Fix EEXIST error returned from afs_rmdir() to be ENOTEMPTY afs: Fix directory format encoding struct netfs: Remove some extraneous directory invalidations cachefiles: Add some subrequest tracepoints cachefiles: Add auxiliary data trace afs: Add more tracepoints to do with tracking validity netfs: Add functions to build/clean a buffer in a folio_queue netfs: Add support for caching single monolithic objects such as AFS dirs afs: Make afs_init_request() get a key if not given a file afs: Use netfslib for directories afs: Use netfslib for symlinks, allowing them to be cached afs: Eliminate afs_read afs: Fix cleanup of immediately failed async calls afs: Make {Y,}FS.FetchData an asynchronous operation netfs: Change the read result collector to only use one work item afs: Make afs_mkdir() locally initialise a new directory's content afs: Use the contained hashtable to search a directory afs: Locally initialise the contents of a new symlink on creation afs: Add a tracepoint for afs_read_receive() netfs: Report on NULL folioq in netfs_writeback_unlock_folios() fs/9p/vfs_addr.c | 6 +- fs/afs/Makefile | 1 + fs/afs/callback.c | 4 +- fs/afs/dir.c | 809 ++++++++++++++++++++------------------ fs/afs/dir_edit.c | 383 ++++++++++-------- fs/afs/dir_search.c | 227 +++++++++++ fs/afs/file.c | 260 ++++++------ fs/afs/fs_operation.c | 113 +++++- fs/afs/fsclient.c | 62 +-- fs/afs/inode.c | 140 ++++++- fs/afs/internal.h | 143 +++++-- fs/afs/main.c | 2 +- fs/afs/mntpt.c | 22 +- fs/afs/rotate.c | 4 +- fs/afs/rxrpc.c | 37 +- fs/afs/super.c | 4 +- fs/afs/validation.c | 31 +- fs/afs/vlclient.c | 1 + fs/afs/write.c | 16 +- fs/afs/xdr_fs.h | 2 +- fs/afs/yfsclient.c | 49 +-- fs/cachefiles/io.c | 4 + fs/cachefiles/xattr.c | 9 +- fs/ceph/addr.c | 22 +- fs/netfs/Makefile | 5 +- fs/netfs/buffered_read.c | 290 +++++--------- fs/netfs/direct_read.c | 78 ++-- fs/netfs/direct_write.c | 10 +- fs/netfs/internal.h | 41 +- fs/netfs/main.c | 6 +- fs/netfs/misc.c | 164 ++++---- fs/netfs/objects.c | 21 +- fs/netfs/read_collect.c | 761 +++++++++++++++++++++-------------- fs/netfs/read_pgpriv2.c | 207 ++++------ fs/netfs/read_retry.c | 209 +++++----- fs/netfs/read_single.c | 195 +++++++++ fs/netfs/rolling_buffer.c | 226 +++++++++++ fs/netfs/stats.c | 4 +- fs/netfs/write_collect.c | 281 +++---------- fs/netfs/write_issue.c | 241 +++++++++++- fs/netfs/write_retry.c | 232 +++++++++++ fs/nfs/fscache.c | 6 +- fs/nfs/fscache.h | 3 +- fs/smb/client/cifssmb.c | 12 +- fs/smb/client/file.c | 3 +- fs/smb/client/smb2ops.c | 2 +- fs/smb/client/smb2pdu.c | 15 +- include/linux/folio_queue.h | 12 +- include/linux/netfs.h | 54 ++- include/linux/rolling_buffer.h | 61 +++ include/trace/events/afs.h | 210 +++++++++- include/trace/events/cachefiles.h | 185 ++++----- include/trace/events/netfs.h | 229 +++++------ lib/kunit_iov_iter.c | 4 +- 54 files changed, 3911 insertions(+), 2207 deletions(-) create mode 100644 fs/afs/dir_search.c create mode 100644 fs/netfs/read_single.c create mode 100644 fs/netfs/rolling_buffer.c create mode 100644 fs/netfs/write_retry.c create mode 100644 include/linux/rolling_buffer.h