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Registered in England and Wales under Company Registration No. 3798903 Subject: [RFC PATCH 53/76] fscache: Implement "will_modify" parameter on fscache_use_cookie() From: David Howells To: Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet Cc: dhowells@redhat.com, Jeff Layton , Matthew Wilcox , Alexander Viro , linux-cachefs@redhat.com, linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 20 Nov 2020 15:13:55 +0000 Message-ID: <160588523556.3465195.5875233390723322661.stgit@warthog.procyon.org.uk> In-Reply-To: <160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk> References: <160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org Implement the "will_modify" parameter passed to fscache_use_cookie(). Setting this to true will henceforth cause the affected object to be marked as dirty on disk, subject to conflict resolution in the event that power failure or a crash occurs or the filesystem operates in disconnected mode. The dirty flag is removed when the fscache_object is discarded from memory. A cache hook is provided to prepare for writing - and this can be used to mark the object on disk. Signed-off-by: David Howells --- fs/cachefiles/interface.c | 68 +++++++++++++++++++++++++++++++++++++++++ fs/cachefiles/internal.h | 2 + fs/cachefiles/xattr.c | 27 ++++++++++++++++ fs/fscache/cookie.c | 15 ++++++++- fs/fscache/internal.h | 1 + fs/fscache/obj.c | 28 ++++++++++++++--- include/linux/fscache-cache.h | 4 ++ 7 files changed, 137 insertions(+), 8 deletions(-) diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c index 4da10640611c..56ae8d956174 100644 --- a/fs/cachefiles/interface.c +++ b/fs/cachefiles/interface.c @@ -208,14 +208,81 @@ static void cachefiles_update_object(struct fscache_object *_object) _leave(""); } +/* + * Shorten the backing object to discard any dirty data and free up + * any unused granules. + */ +static bool cachefiles_shorten_object(struct cachefiles_object *object, loff_t new_size) +{ + struct cachefiles_cache *cache; + struct inode *inode; + struct path path; + loff_t i_size; + int ret; + + cache = container_of(object->fscache.cache, + struct cachefiles_cache, cache); + path.mnt = cache->mnt; + path.dentry = object->dentry; + + inode = d_inode(object->dentry); + trace_cachefiles_trunc(object, inode, i_size_read(inode), new_size); + ret = vfs_truncate(&path, new_size); + if (ret < 0) { + cachefiles_io_error_obj(object, "Trunc-to-size failed %d", ret); + cachefiles_remove_object_xattr(cache, object->dentry); + return false; + } + + new_size = round_up(new_size, CACHEFILES_DIO_BLOCK_SIZE); + i_size = i_size_read(inode); + if (i_size < new_size) { + trace_cachefiles_trunc(object, inode, i_size, new_size); + ret = vfs_truncate(&path, new_size); + if (ret < 0) { + cachefiles_io_error_obj(object, "Trunc-to-dio-size failed %d", ret); + cachefiles_remove_object_xattr(cache, object->dentry); + return false; + } + } + + return true; +} + +/* + * Trim excess stored data off of an object. + */ +static bool cachefiles_trim_object(struct cachefiles_object *object) +{ + loff_t object_size; + + _enter("{OBJ%x}", object->fscache.debug_id); + + object_size = object->fscache.cookie->object_size; + if (i_size_read(d_inode(object->dentry)) <= object_size) + return true; + + return cachefiles_shorten_object(object, object_size); +} + /* * Commit changes to the object as we drop it. */ static bool cachefiles_commit_object(struct cachefiles_object *object, struct cachefiles_cache *cache) { + bool update = false; + if (object->content_map_changed) cachefiles_save_content_map(object); + if (test_and_clear_bit(FSCACHE_OBJECT_LOCAL_WRITE, &object->fscache.flags)) + update = true; + if (test_and_clear_bit(FSCACHE_OBJECT_NEEDS_UPDATE, &object->fscache.flags)) + update = true; + if (update) { + if (cachefiles_trim_object(object)) + cachefiles_set_object_xattr(object); + } if (test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) return cachefiles_commit_tmpfile(cache, object); @@ -591,5 +658,6 @@ const struct fscache_cache_ops cachefiles_cache_ops = { .get_object_usage = cachefiles_get_object_usage, .sync_cache = cachefiles_sync_cache, .begin_operation = cachefiles_begin_operation, + .prepare_to_write = cachefiles_prepare_to_write, .display_object = cachefiles_display_object, }; diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h index af68564598d5..e2d06c0860a2 100644 --- a/fs/cachefiles/internal.h +++ b/fs/cachefiles/internal.h @@ -258,7 +258,7 @@ extern int cachefiles_set_object_xattr(struct cachefiles_object *object); extern int cachefiles_check_auxdata(struct cachefiles_object *object); extern int cachefiles_remove_object_xattr(struct cachefiles_cache *cache, struct dentry *dentry); - +extern int cachefiles_prepare_to_write(struct fscache_object *object); /* * error handling diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c index 991ecda1f140..2f8623a7b864 100644 --- a/fs/cachefiles/xattr.c +++ b/fs/cachefiles/xattr.c @@ -124,6 +124,8 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object) buf->zero_point = cpu_to_be64(object->fscache.cookie->zero_point); buf->type = object->fscache.cookie->type; buf->content = object->content_info; + if (test_bit(FSCACHE_OBJECT_LOCAL_WRITE, &object->fscache.flags)) + buf->content = CACHEFILES_CONTENT_DIRTY; if (len > 0) memcpy(buf->data, fscache_get_aux(object->fscache.cookie), len); @@ -184,6 +186,10 @@ int cachefiles_check_auxdata(struct cachefiles_object *object) why = cachefiles_coherency_check_aux; } else if (be64_to_cpu(buf->object_size) != object->fscache.cookie->object_size) { why = cachefiles_coherency_check_objsize; + } else if (buf->content == CACHEFILES_CONTENT_DIRTY) { + // TODO: Begin conflict resolution + pr_warn("Dirty object in cache\n"); + why = cachefiles_coherency_check_dirty; } else { object->fscache.cookie->zero_point = be64_to_cpu(buf->zero_point); object->content_info = buf->content; @@ -219,3 +225,24 @@ int cachefiles_remove_object_xattr(struct cachefiles_cache *cache, _leave(" = %d", ret); return ret; } + +/* + * Stick a marker on the cache object to indicate that it's dirty. + */ +int cachefiles_prepare_to_write(struct fscache_object *_object) +{ + int ret; + const struct cred *saved_cred; + struct cachefiles_object *object = + container_of(_object, struct cachefiles_object, fscache); + struct cachefiles_cache *cache = + container_of(_object->cache, struct cachefiles_cache, cache); + + _enter("c=%08x", object->fscache.cookie->debug_id); + + cachefiles_begin_secure(cache, &saved_cred); + ret = cachefiles_set_object_xattr(object); + cachefiles_end_secure(cache, saved_cred); + + return ret; +} diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c index d20028535a86..bfea035af06d 100644 --- a/fs/fscache/cookie.c +++ b/fs/fscache/cookie.c @@ -363,6 +363,8 @@ EXPORT_SYMBOL(__fscache_acquire_cookie); void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify) { enum fscache_cookie_stage stage; + struct fscache_object *object; + bool write_set; _enter("c=%08x", cookie->debug_id); @@ -398,8 +400,17 @@ void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify) case FSCACHE_COOKIE_STAGE_NO_DATA_YET: case FSCACHE_COOKIE_STAGE_ACTIVE: case FSCACHE_COOKIE_STAGE_INVALIDATING: - // TODO: Handle will_modify - spin_unlock(&cookie->lock); + if (will_modify) { + object = hlist_entry(cookie->backing_objects.first, + struct fscache_object, cookie_link); + write_set = test_and_set_bit(FSCACHE_OBJECT_LOCAL_WRITE, + &object->flags); + spin_unlock(&cookie->lock); + if (!write_set) + fscache_dispatch(cookie, object, 0, fscache_prepare_to_write); + } else { + spin_unlock(&cookie->lock); + } break; case FSCACHE_COOKIE_STAGE_FAILED: diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h index 73568e84fe3d..3c408da2c837 100644 --- a/fs/fscache/internal.h +++ b/fs/fscache/internal.h @@ -152,6 +152,7 @@ extern void fscache_lookup_object(struct fscache_cookie *, struct fscache_object extern void fscache_invalidate_object(struct fscache_cookie *, struct fscache_object *, int); extern void fscache_drop_object(struct fscache_cookie *, struct fscache_object *, bool); extern void fscache_relinquish_objects(struct fscache_cookie *, struct fscache_object *, int); +extern void fscache_prepare_to_write(struct fscache_cookie *, struct fscache_object *, int); /* * object-list.c diff --git a/fs/fscache/obj.c b/fs/fscache/obj.c index 60c70c0e474d..a36de6af2182 100644 --- a/fs/fscache/obj.c +++ b/fs/fscache/obj.c @@ -117,7 +117,8 @@ static bool fscache_wrangle_object(struct fscache_cookie *cookie, * Create an object chain, making sure that the index chain is fully created. */ static struct fscache_object *fscache_lookup_object_chain(struct fscache_cookie *cookie, - struct fscache_cache *cache) + struct fscache_cache *cache, + bool will_modify) { struct fscache_object *object = NULL, *parent, *xobject; @@ -131,7 +132,7 @@ static struct fscache_object *fscache_lookup_object_chain(struct fscache_cookie spin_unlock(&cookie->lock); /* Recurse to look up/create the parent index. */ - parent = fscache_lookup_object_chain(cookie->parent, cache); + parent = fscache_lookup_object_chain(cookie->parent, cache, false); if (!parent) goto error; @@ -146,6 +147,9 @@ static struct fscache_object *fscache_lookup_object_chain(struct fscache_cookie if (!object) goto error; + if (will_modify) + __set_bit(FSCACHE_OBJECT_LOCAL_WRITE, &object->flags); + xobject = fscache_attach_object(cookie, object); if (xobject != object) { fscache_do_put_object(object, fscache_obj_put_alloc_dup); @@ -207,7 +211,8 @@ static struct fscache_object *fscache_lookup_object_chain(struct fscache_cookie * - this must make sure the index chain is instantiated and instantiate the * object representation too */ -static void fscache_lookup_object_locked(struct fscache_cookie *cookie) +static void fscache_lookup_object_locked(struct fscache_cookie *cookie, + bool will_modify) { struct fscache_object *object; struct fscache_cache *cache; @@ -225,12 +230,16 @@ static void fscache_lookup_object_locked(struct fscache_cookie *cookie) _debug("cache %s", cache->tag->name); - object = fscache_lookup_object_chain(cookie, cache); + object = fscache_lookup_object_chain(cookie, cache, will_modify); if (!object) { _leave(" [fail]"); return; } + if (will_modify && + test_and_set_bit(FSCACHE_OBJECT_LOCAL_WRITE, &object->flags)) + fscache_prepare_to_write(cookie, object, 0); + fscache_do_put_object(object, fscache_obj_put); _leave(" [done]"); } @@ -239,7 +248,7 @@ void fscache_lookup_object(struct fscache_cookie *cookie, struct fscache_object *object, int param) { down_read(&fscache_addremove_sem); - fscache_lookup_object_locked(cookie); + fscache_lookup_object_locked(cookie, param); up_read(&fscache_addremove_sem); __fscache_unuse_cookie(cookie, NULL, NULL); } @@ -354,3 +363,12 @@ void fscache_relinquish_objects(struct fscache_cookie *cookie, fscache_drop_cookie(cookie); } + +/* + * Prepare a cache object to be written to. + */ +void fscache_prepare_to_write(struct fscache_cookie *cookie, + struct fscache_object *object, int param) +{ + object->cache->ops->prepare_to_write(object); +} diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h index a0bb526735b5..eb303deb39c1 100644 --- a/include/linux/fscache-cache.h +++ b/include/linux/fscache-cache.h @@ -142,6 +142,9 @@ struct fscache_cache_ops { /* Begin an operation on a cache object */ void (*begin_operation)(struct fscache_op_resources *opr); + /* Prepare to write to a live cache object */ + int (*prepare_to_write)(struct fscache_object *object); + /* Display object info in /proc/fs/fscache/objects */ int (*display_object)(struct seq_file *m, struct fscache_object *object); }; @@ -170,6 +173,7 @@ struct fscache_object { spinlock_t lock; /* state and operations lock */ unsigned long flags; +#define FSCACHE_OBJECT_LOCAL_WRITE 1 /* T if the object is being modified locally */ #define FSCACHE_OBJECT_NEEDS_INVAL 8 /* T if object needs invalidation */ #define FSCACHE_OBJECT_NEEDS_UPDATE 9 /* T if object attrs need writing to disk */