[v2,18/53] fscache: Implement simple cookie state machine

Message ID	163492940195.1038219.17728963178964131703.stgit@warthog.procyon.org.uk (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-cifs-owner@kernel.org> Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH v2 18/53] fscache: Implement simple cookie state machine From: David Howells <dhowells@redhat.com> To: linux-cachefs@redhat.com Cc: dhowells@redhat.com, Trond Myklebust <trondmy@hammerspace.com>, Anna Schumaker <anna.schumaker@netapp.com>, Steve French <sfrench@samba.org>, Dominique Martinet <asmadeus@codewreck.org>, Jeff Layton <jlayton@kernel.com>, Matthew Wilcox <willy@infradead.org>, Alexander Viro <viro@zeniv.linux.org.uk>, Omar Sandoval <osandov@osandov.com>, Linus Torvalds <torvalds@linux-foundation.org>, 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, 22 Oct 2021 20:03:22 +0100 Message-ID: <163492940195.1038219.17728963178964131703.stgit@warthog.procyon.org.uk> In-Reply-To: <163492911924.1038219.13107463173777870713.stgit@warthog.procyon.org.uk> References: <163492911924.1038219.13107463173777870713.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk
Series	fscache: Rewrite index API and management system \| expand [v2,00/53] fscache: Rewrite index API and management system [v2,02/53] fscache_old: Rename CONFIG_FSCACHE* to CONFIG_FSCACHE_OLD* [v2,04/53] cachefiles_old: Rename CONFIG_CACHEFILES* to CONFIG_CACHEFILES_OLD* [v2,05/53] netfs: Display the netfs inode number in the netfs_read tracepoint [v2,06/53] netfs: Pass a flag to ->prepare_write() to say if there's no alloc'd space [v2,07/53] fscache: Introduce new driver [v2,08/53] fscache: Implement a hash function [v2,09/53] fscache: Implement cache registration [v2,10/53] fscache: Implement volume registration [v2,11/53] fscache: Implement cookie registration [v2,12/53] fscache: Implement cache-level access helpers [v2,13/53] fscache: Implement volume-level access helpers [v2,14/53] fscache: Implement cookie-level access helpers [v2,15/53] fscache: Implement functions add/remove a cache [v2,16/53] fscache: Provide and use cache methods to lookup/create/free a volume [v2,17/53] fscache: Add a function for a cache backend to note an I/O error [v2,18/53] fscache: Implement simple cookie state machine [v2,19/53] fscache: Implement cookie user counting and resource pinning [v2,20/53] fscache: Implement cookie invalidation [v2,21/53] fscache: Provide a means to begin an operation [v2,22/53] fscache: Provide read/write stat counters for the cache [v2,23/53] fscache: Provide a function to let the netfs update its coherency data [v2,24/53] fscache: Implement I/O interface [v2,25/53] fscache: Provide fallback I/O functions [v2,26/53] vfs, fscache: Implement pinning of cache usage for writeback [v2,27/53] fscache: Provide a function to note the release of a page [v2,28/53] fscache: Provide a function to resize a cookie [v2,29/53] cachefiles: Introduce new driver [v2,30/53] cachefiles: Add some error injection support [v2,31/53] cachefiles: Define structs [v2,32/53] cachefiles: Add a couple of tracepoints for logging errors [v2,33/53] cachefiles: Add I/O error reporting macros [v2,34/53] cachefiles: Provide a function to check how much space there is [v2,35/53] cachefiles: Implement a function to get/create a directory in the cache [v2,36/53] cachefiles: Implement daemon UAPI and cache registration [v2,37/53] cachefiles: Implement volume support [v2,38/53] cachefiles: Implement data storage object handling [v2,39/53] cachefiles: Implement begin and end I/O [v2,40/53] cachefiles: Implement the I/O routines [v2,41/53] afs: Handle len being extending over page end in write_begin/write_end [v2,42/53] afs: Fix afs_write_end() to handle len > page size [v2,43/53] afs: Make afs_write_begin() return the THP subpage [v2,44/53] afs: Convert afs to use the new fscache API [v2,45/53] afs: Copy local writes to the cache when writing to the server [v2,46/53] afs: Skip truncation on the server of data we haven't written yet [v2,47/53] afs: Add synchronous O_DIRECT support [v2,48/53] 9p: Use fscache indexing rewrite and reenable caching [v2,49/53] 9p: Copy local writes to the cache when writing to the server [v2,50/53] nfs: Convert to new fscache volume/cookie API [v2,51/53] cifs: Support fscache indexing rewrite (untested) [v2,52/53] fscache, cachefiles: Display stats of no-space events [v2,53/53] fscache, cachefiles: Display stat of culling events

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c index 9b6ddbc01825..b7373ebcaf56 100644 --- a/fs/fscache/cookie.c +++ b/fs/fscache/cookie.c @@ -15,7 +15,9 @@ struct kmem_cache *fscache_cookie_jar; +static void fscache_cookie_worker(struct work_struct *work); static void fscache_drop_cookie(struct fscache_cookie *cookie); +static void fscache_lookup_cookie(struct fscache_cookie *cookie); #define fscache_cookie_hash_shift 15 static struct hlist_bl_head fscache_cookie_hash[1 << fscache_cookie_hash_shift]; @@ -57,13 +59,26 @@ static void fscache_free_cookie(struct fscache_cookie *cookie) kmem_cache_free(fscache_cookie_jar, cookie); } +static void __fscache_queue_cookie(struct fscache_cookie *cookie) +{ + if (!queue_work(fscache_wq, &cookie->work)) + fscache_put_cookie(cookie, fscache_cookie_put_over_queued); +} + +static void fscache_queue_cookie(struct fscache_cookie *cookie, + enum fscache_cookie_trace where) +{ + fscache_get_cookie(cookie, where); + __fscache_queue_cookie(cookie); +} + static void __fscache_end_cookie_access(struct fscache_cookie *cookie) { if (test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_RELINQUISHING); else if (test_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags)) fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_WITHDRAWING); - // PLACEHOLDER: Schedule cookie cleanup + fscache_queue_cookie(cookie, fscache_cookie_get_end_access); } /* @@ -252,7 +267,7 @@ static struct fscache_cookie *fscache_alloc_cookie( cookie->stage = FSCACHE_COOKIE_STAGE_QUIESCENT; spin_lock_init(&cookie->lock); INIT_LIST_HEAD(&cookie->commit_link); - INIT_WORK(&cookie->work, NULL /* PLACEHOLDER */); + INIT_WORK(&cookie->work, fscache_cookie_worker); write_lock(&fscache_cookies_lock); list_add_tail(&cookie->proc_link, &fscache_cookies); @@ -374,6 +389,136 @@ struct fscache_cookie *__fscache_acquire_cookie( } EXPORT_SYMBOL(__fscache_acquire_cookie); +/* + * Prepare a cache object to be written to. + */ +static void fscache_prepare_to_write(struct fscache_cookie *cookie) +{ + cookie->volume->cache->ops->prepare_to_write(cookie); +} + +/* + * Look up a cookie to the cache. + */ +static void fscache_lookup_cookie(struct fscache_cookie *cookie) +{ + bool changed_stage = false, need_withdraw = false, prep_write = false; + + _enter(""); + + if (!cookie->volume->cache_priv) { + fscache_create_volume(cookie->volume, true); + if (!cookie->volume->cache_priv) { + fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_QUIESCENT); + goto out; + } + } + + if (!cookie->volume->cache->ops->lookup_cookie(cookie)) { + if (cookie->stage != FSCACHE_COOKIE_STAGE_FAILED) + fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_QUIESCENT); + need_withdraw = true; + _leave(" [fail]"); + goto out; + } + + spin_lock(&cookie->lock); + if (cookie->stage != FSCACHE_COOKIE_STAGE_RELINQUISHING) { + prep_write = test_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags); + __fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_ACTIVE); + fscache_see_cookie(cookie, fscache_cookie_see_active); + changed_stage = true; + } + spin_unlock(&cookie->lock); + if (changed_stage) + wake_up_cookie_stage(cookie); + if (prep_write) + fscache_prepare_to_write(cookie); + +out: + fscache_end_cookie_access(cookie, fscache_access_lookup_cookie_end); + if (need_withdraw) + fscache_withdraw_cookie(cookie); + fscache_end_volume_access(cookie->volume, fscache_access_lookup_cookie_end); +} + +/* + * Perform work upon the cookie, such as committing its cache state, + * relinquishing it or withdrawing the backing cache. We're protected from the + * cache going away under us as object withdrawal must come through this + * non-reentrant work item. + */ +static void __fscache_cookie_worker(struct fscache_cookie *cookie) +{ + _enter("c=%x", cookie->debug_id); + +again: + switch (READ_ONCE(cookie->stage)) { + case FSCACHE_COOKIE_STAGE_ACTIVE: + if (test_and_clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags)) + fscache_prepare_to_write(cookie); + break; + + case FSCACHE_COOKIE_STAGE_LOOKING_UP: + fscache_lookup_cookie(cookie); + goto again; + + case FSCACHE_COOKIE_STAGE_CREATING: + WARN_ONCE(1, "Cookie %x in unexpected stage %u\n", + cookie->debug_id, cookie->stage); + break; + + case FSCACHE_COOKIE_STAGE_FAILED: + break; + + case FSCACHE_COOKIE_STAGE_RELINQUISHING: + case FSCACHE_COOKIE_STAGE_WITHDRAWING: + if (test_and_clear_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags) && + cookie->cache_priv) + cookie->volume->cache->ops->withdraw_cookie(cookie); + if (cookie->stage == FSCACHE_COOKIE_STAGE_RELINQUISHING) { + fscache_see_cookie(cookie, fscache_cookie_see_relinquish); + fscache_drop_cookie(cookie); + break; + } else { + fscache_see_cookie(cookie, fscache_cookie_see_withdraw); + } + fallthrough; + + case FSCACHE_COOKIE_STAGE_QUIESCENT: + case FSCACHE_COOKIE_STAGE_DROPPED: + clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags); + clear_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags); + clear_bit(FSCACHE_COOKIE_DO_COMMIT, &cookie->flags); + clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags); + set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags); + fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_QUIESCENT); + break; + } + _leave(""); +} + +static void fscache_cookie_worker(struct work_struct *work) +{ + struct fscache_cookie *cookie = container_of(work, struct fscache_cookie, work); + + fscache_see_cookie(cookie, fscache_cookie_see_work); + __fscache_cookie_worker(cookie); + fscache_put_cookie(cookie, fscache_cookie_put_work); +} + +/* + * Wait for the object to become inactive. The cookie's work item will be + * scheduled when someone transitions n_accesses to 0. + */ +static void __fscache_withdraw_cookie(struct fscache_cookie *cookie) +{ + if (test_and_clear_bit(FSCACHE_COOKIE_NACC_ELEVATED, &cookie->flags)) + fscache_end_cookie_access(cookie, fscache_access_cache_unpin); + else + __fscache_end_cookie_access(cookie); +} + /* * Remove a cookie from the hash table. */ @@ -404,6 +549,25 @@ static void fscache_drop_cookie(struct fscache_cookie *cookie) fscache_stat(&fscache_n_relinquishes_dropped); } +static void fscache_drop_withdraw_cookie(struct fscache_cookie *cookie) +{ + __fscache_withdraw_cookie(cookie); +} + +/** + * fscache_withdraw_cookie - Mark a cookie for withdrawal + * @cookie: The cookie to be withdrawn. + * + * Allow the cache backend to withdraw the backing for a cookie for its own + * reasons, even if that cookie is in active use. + */ +void fscache_withdraw_cookie(struct fscache_cookie *cookie) +{ + set_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags); + fscache_drop_withdraw_cookie(cookie); +} +EXPORT_SYMBOL(fscache_withdraw_cookie); + /* * Allow the netfs to release a cookie back to the cache. * - the object will be marked as recyclable on disk if retire is true @@ -432,7 +596,7 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire) set_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags); if (test_bit(FSCACHE_COOKIE_HAS_BEEN_CACHED, &cookie->flags)) - ; // PLACEHOLDER: Do something here if the cookie was cached + fscache_drop_withdraw_cookie(cookie); else fscache_drop_cookie(cookie); fscache_put_cookie(cookie, fscache_cookie_put_relinquish); diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h index dfecabfd4a0e..f6d63dc0ffa9 100644 --- a/include/linux/fscache-cache.h +++ b/include/linux/fscache-cache.h @@ -59,6 +59,15 @@ struct fscache_cache_ops { /* Free the cache's data attached to a volume */ void (*free_volume)(struct fscache_volume *volume); + + /* Look up a cookie in the cache */ + bool (*lookup_cookie)(struct fscache_cookie *cookie); + + /* Withdraw an object without any cookie access counts held */ + void (*withdraw_cookie)(struct fscache_cookie *cookie); + + /* Prepare to write to a live cache object */ + void (*prepare_to_write)(struct fscache_cookie *cookie); }; static inline enum fscache_cache_state fscache_cache_state(const struct fscache_cache *cache) @@ -96,6 +105,7 @@ extern int fscache_add_cache(struct fscache_cache *cache, extern void fscache_put_cache(struct fscache_cache *cache, enum fscache_cache_trace where); extern void fscache_withdraw_cache(struct fscache_cache *cache); +extern void fscache_withdraw_cookie(struct fscache_cookie *cookie); extern void fscache_io_error(struct fscache_cache *cache); diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h index 3476cc7fdb25..00ffe0f8e6d3 100644 --- a/include/trace/events/fscache.h +++ b/include/trace/events/fscache.h @@ -67,6 +67,7 @@ enum fscache_access_trace { fscache_access_acquire_volume_end, fscache_access_cache_pin, fscache_access_cache_unpin, + fscache_access_lookup_cookie_end, fscache_access_relinquish_volume, fscache_access_relinquish_volume_end, fscache_access_unlive, @@ -122,6 +123,7 @@ enum fscache_access_trace { EM(fscache_access_acquire_volume_end, "END acq_vol") \ EM(fscache_access_cache_pin, "PIN cache ") \ EM(fscache_access_cache_unpin, "UNPIN cache ") \ + EM(fscache_access_lookup_cookie_end, "END lookup ") \ EM(fscache_access_relinquish_volume, "BEGIN rlq_vol") \ EM(fscache_access_relinquish_volume_end,"END rlq_vol") \ E_(fscache_access_unlive, "END unlive ")

[v2,18/53] fscache: Implement simple cookie state machine

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