[17/64] fscache: Implement simple cookie state machine

Message ID	163819599657.215744.15799615296912341745.stgit@warthog.procyon.org.uk (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-nfs-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 17/64] 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.org>, 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: Mon, 29 Nov 2021 14:26:36 +0000 Message-ID: <163819599657.215744.15799615296912341745.stgit@warthog.procyon.org.uk> In-Reply-To: <163819575444.215744.318477214576928110.stgit@warthog.procyon.org.uk> References: <163819575444.215744.318477214576928110.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, cachefiles: Rewrite \| expand [00/64] fscache, cachefiles: Rewrite [01/64] fscache, cachefiles: Disable configuration [04/64] netfs: Display the netfs inode number in the netfs_read tracepoint [05/64] netfs: Pass a flag to ->prepare_write() to say if there's no alloc'd space [06/64] fscache: Introduce new driver [07/64] fscache: Implement a hash function [08/64] fscache: Implement cache registration [09/64] fscache: Implement volume registration [10/64] fscache: Implement cookie registration [11/64] fscache: Implement cache-level access helpers [12/64] fscache: Implement volume-level access helpers [13/64] fscache: Implement cookie-level access helpers [14/64] fscache: Implement functions add/remove a cache [15/64] fscache: Provide and use cache methods to lookup/create/free a volume [16/64] fscache: Add a function for a cache backend to note an I/O error [17/64] fscache: Implement simple cookie state machine [18/64] fscache: Implement cookie user counting and resource pinning [19/64] fscache: Implement cookie invalidation [20/64] fscache: Provide a means to begin an operation [21/64] fscache: Count data storage objects in a cache [22/64] fscache: Provide read/write stat counters for the cache [23/64] fscache: Provide a function to let the netfs update its coherency data [24/64] netfs: Pass more information on how to deal with a hole in the cache [25/64] fscache: Implement raw I/O interface [26/64] fscache: Implement higher-level write I/O interface [27/64] vfs, fscache: Implement pinning of cache usage for writeback [28/64] fscache: Provide a function to note the release of a page [29/64] fscache: Provide a function to resize a cookie [30/64] cachefiles: Introduce rewritten driver [31/64] cachefiles: Define structs [32/64] cachefiles: Add some error injection support [33/64] cachefiles: Add a couple of tracepoints for logging errors [34/64] cachefiles: Add cache error reporting macro [35/64] cachefiles: Add security derivation [36/64] cachefiles: Register a miscdev and parse commands over it [37/64] cachefiles: Provide a function to check how much space there is [38/64] vfs, cachefiles: Mark a backing file in use with an inode flag [39/64] cachefiles: Implement a function to get/create a directory in the cache [40/64] cachefiles: Implement cache registration and withdrawal [41/64] cachefiles: Implement volume support [42/64] cachefiles: Add tracepoints for calls to the VFS [43/64] cachefiles: Implement object lifecycle funcs [44/64] cachefiles: Implement key to filename encoding [45/64] cachefiles: Implement metadata/coherency data storage in xattrs [46/64] cachefiles: Mark a backing file in use with an inode flag [47/64] cachefiles: Implement culling daemon commands [48/64] cachefiles: Implement backing file wrangling [49/64] cachefiles: Implement begin and end I/O operation [50/64] cachefiles: Implement cookie resize for truncate [51/64] cachefiles: Implement the I/O routines [52/64] cachefiles: Allow cachefiles to actually function [53/64] fscache, cachefiles: Display stats of no-space events [54/64] fscache, cachefiles: Display stat of culling events [55/64] afs: Handle len being extending over page end in write_begin/write_end [56/64] afs: Fix afs_write_end() to handle len > page size [57/64] afs: Convert afs to use the new fscache API [58/64] afs: Copy local writes to the cache when writing to the server [59/64] afs: Skip truncation on the server of data we haven't written yet [60/64] 9p: Use fscache indexing rewrite and reenable caching [61/64] 9p: Copy local writes to the cache when writing to the server [62/64] nfs: Convert to new fscache volume/cookie API [63/64] cifs: Support fscache indexing rewrite (untested)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c index 3dd150182d97..51bf52ea712c 100644 --- a/fs/fscache/cookie.c +++ b/fs/fscache/cookie.c @@ -15,7 +15,8 @@ struct kmem_cache *fscache_cookie_jar; -static void fscache_drop_cookie(struct fscache_cookie *cookie); +static void fscache_cookie_worker(struct work_struct *work); +static void fscache_unhash_cookie(struct fscache_cookie *cookie); #define fscache_cookie_hash_shift 15 static struct hlist_bl_head fscache_cookie_hash[1 << fscache_cookie_hash_shift]; @@ -57,6 +58,19 @@ 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); +} + /* * Initialise the access gate on a cookie by keeping its n_accesses counter * raised by 1. This will prevent end-access from transitioning it to 0 until @@ -72,15 +86,6 @@ static void fscache_init_access_gate(struct fscache_cookie *cookie) set_bit(FSCACHE_COOKIE_NACC_ELEVATED, &cookie->flags); } -static void __fscache_end_cookie_access(struct fscache_cookie *cookie) -{ - if (test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) - fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_RELINQUISHING); - else if (test_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags)) - fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_WITHDRAWING); - // PLACEHOLDER: Schedule cookie cleanup -} - /** * fscache_end_cookie_access - Unpin a cache at the end of an access. * @cookie: A data file cookie @@ -101,7 +106,7 @@ void fscache_end_cookie_access(struct fscache_cookie *cookie, trace_fscache_access(cookie->debug_id, refcount_read(&cookie->ref), n_accesses, why); if (n_accesses == 0) - __fscache_end_cookie_access(cookie); + fscache_queue_cookie(cookie, fscache_cookie_get_end_access); } EXPORT_SYMBOL(fscache_end_cookie_access); @@ -172,35 +177,58 @@ static inline void wake_up_cookie_state(struct fscache_cookie *cookie) wake_up_var(&cookie->state); } +/* + * Change the state a cookie is at and wake up anyone waiting for that. Impose + * an ordering between the stuff stored in the cookie and the state member. + * Paired with fscache_cookie_state(). + */ static void __fscache_set_cookie_state(struct fscache_cookie *cookie, enum fscache_cookie_state state) { - cookie->state = state; + smp_store_release(&cookie->state, state); } -/* - * Change the state a cookie is at and wake up anyone waiting for that - but - * only if the cookie isn't already marked as being in a cleanup state. - */ -void fscache_set_cookie_state(struct fscache_cookie *cookie, - enum fscache_cookie_state state) +static void fscache_set_cookie_state(struct fscache_cookie *cookie, + enum fscache_cookie_state state) { - bool changed = false; - spin_lock(&cookie->lock); - switch (cookie->state) { - case FSCACHE_COOKIE_STATE_RELINQUISHING: - break; - default: - __fscache_set_cookie_state(cookie, state); - changed = true; - break; - } + __fscache_set_cookie_state(cookie, state); spin_unlock(&cookie->lock); - if (changed) - wake_up_cookie_state(cookie); + wake_up_cookie_state(cookie); +} + +/** + * fscache_cookie_lookup_negative - Note negative lookup + * @cookie: The cookie that was being looked up + * + * Note that some part of the metadata path in the cache doesn't exist and so + * we can release any waiting readers in the certain knowledge that there's + * nothing for them to actually read. + * + * This function uses no locking and must only be called from the state machine. + */ +void fscache_cookie_lookup_negative(struct fscache_cookie *cookie) +{ + set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags); + fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_CREATING); } -EXPORT_SYMBOL(fscache_set_cookie_state); +EXPORT_SYMBOL(fscache_cookie_lookup_negative); + +/** + * fscache_caching_failed - Report that a failure stopped caching on a cookie + * @cookie: The cookie that was affected + * + * Tell fscache that caching on a cookie needs to be stopped due to some sort + * of failure. + * + * This function uses no locking and must only be called from the state machine. + */ +void fscache_caching_failed(struct fscache_cookie *cookie) +{ + clear_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags); + fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_FAILED); +} +EXPORT_SYMBOL(fscache_caching_failed); /* * Set the index key in a cookie. The cookie struct has space for a 16-byte @@ -293,10 +321,10 @@ static struct fscache_cookie *fscache_alloc_cookie( refcount_set(&cookie->ref, 1); cookie->debug_id = atomic_inc_return(&fscache_cookie_debug_id); - cookie->state = FSCACHE_COOKIE_STATE_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); + __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT); write_lock(&fscache_cookies_lock); list_add_tail(&cookie->proc_link, &fscache_cookies); @@ -418,6 +446,184 @@ 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 in the cache. + */ +static void fscache_perform_lookup(struct fscache_cookie *cookie) +{ + enum fscache_access_trace trace = fscache_access_lookup_cookie_end_failed; + bool need_withdraw = false; + + _enter(""); + + if (!cookie->volume->cache_priv) { + fscache_create_volume(cookie->volume, true); + if (!cookie->volume->cache_priv) { + fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT); + goto out; + } + } + + if (!cookie->volume->cache->ops->lookup_cookie(cookie)) { + if (cookie->state != FSCACHE_COOKIE_STATE_FAILED) + fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT); + need_withdraw = true; + _leave(" [fail]"); + goto out; + } + + fscache_see_cookie(cookie, fscache_cookie_see_active); + fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_ACTIVE); + trace = fscache_access_lookup_cookie_end; + +out: + fscache_end_cookie_access(cookie, trace); + if (need_withdraw) + fscache_withdraw_cookie(cookie); + fscache_end_volume_access(cookie->volume, cookie, trace); +} + +/* + * 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_state_machine(struct fscache_cookie *cookie) +{ + enum fscache_cookie_state state; + bool wake = false; + + _enter("c=%x", cookie->debug_id); + +again: + spin_lock(&cookie->lock); +again_locked: + state = cookie->state; + switch (state) { + case FSCACHE_COOKIE_STATE_QUIESCENT: + /* The QUIESCENT state is jumped to the LOOKING_UP state by + * fscache_use_cookie(). + */ + + if (atomic_read(&cookie->n_accesses) == 0 && + test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) { + __fscache_set_cookie_state(cookie, + FSCACHE_COOKIE_STATE_RELINQUISHING); + wake = true; + goto again_locked; + } + break; + + case FSCACHE_COOKIE_STATE_LOOKING_UP: + spin_unlock(&cookie->lock); + fscache_init_access_gate(cookie); + fscache_perform_lookup(cookie); + goto again; + + case FSCACHE_COOKIE_STATE_ACTIVE: + if (test_and_clear_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags)) { + spin_unlock(&cookie->lock); + fscache_prepare_to_write(cookie); + spin_lock(&cookie->lock); + } + fallthrough; + + case FSCACHE_COOKIE_STATE_FAILED: + if (atomic_read(&cookie->n_accesses) != 0) + break; + if (test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) { + __fscache_set_cookie_state(cookie, + FSCACHE_COOKIE_STATE_RELINQUISHING); + wake = true; + goto again_locked; + } + if (test_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags)) { + __fscache_set_cookie_state(cookie, + FSCACHE_COOKIE_STATE_WITHDRAWING); + wake = true; + goto again_locked; + } + break; + + case FSCACHE_COOKIE_STATE_RELINQUISHING: + case FSCACHE_COOKIE_STATE_WITHDRAWING: + if (cookie->cache_priv) { + spin_unlock(&cookie->lock); + cookie->volume->cache->ops->withdraw_cookie(cookie); + spin_lock(&cookie->lock); + } + + switch (state) { + case FSCACHE_COOKIE_STATE_RELINQUISHING: + fscache_see_cookie(cookie, fscache_cookie_see_relinquish); + fscache_unhash_cookie(cookie); + __fscache_set_cookie_state(cookie, + FSCACHE_COOKIE_STATE_DROPPED); + wake = true; + goto out; + case FSCACHE_COOKIE_STATE_WITHDRAWING: + fscache_see_cookie(cookie, fscache_cookie_see_withdraw); + break; + default: + BUG(); + } + + clear_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags); + clear_bit(FSCACHE_COOKIE_DO_WITHDRAW, &cookie->flags); + clear_bit(FSCACHE_COOKIE_DO_LRU_DISCARD, &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_state(cookie, FSCACHE_COOKIE_STATE_QUIESCENT); + wake = true; + break; + + case FSCACHE_COOKIE_STATE_DROPPED: + break; + + default: + WARN_ONCE(1, "Cookie %x in unexpected state %u\n", + cookie->debug_id, state); + break; + } + +out: + spin_unlock(&cookie->lock); + if (wake) + wake_up_cookie_state(cookie); + _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_state_machine(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 - but if someone's + * already done that, schedule it anyway. + */ +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_queue_cookie(cookie, fscache_cookie_get_end_access); +} + /* * Remove a cookie from the hash table. */ @@ -432,21 +638,27 @@ static void fscache_unhash_cookie(struct fscache_cookie *cookie) hlist_bl_lock(h); hlist_bl_del(&cookie->hash_link); hlist_bl_unlock(h); + fscache_stat(&fscache_n_relinquishes_dropped); } -/* - * Finalise a cookie after all its resources have been disposed of. - */ -static void fscache_drop_cookie(struct fscache_cookie *cookie) +static void fscache_drop_withdraw_cookie(struct fscache_cookie *cookie) { - spin_lock(&cookie->lock); - __fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_DROPPED); - spin_unlock(&cookie->lock); - wake_up_cookie_state(cookie); + __fscache_withdraw_cookie(cookie); +} - fscache_unhash_cookie(cookie); - fscache_stat(&fscache_n_relinquishes_dropped); +/** + * 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. @@ -473,12 +685,13 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire) ASSERTCMP(atomic_read(&cookie->volume->n_cookies), >, 0); atomic_dec(&cookie->volume->n_cookies); - 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 - else - fscache_drop_cookie(cookie); + if (test_bit(FSCACHE_COOKIE_HAS_BEEN_CACHED, &cookie->flags)) { + set_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags); + fscache_drop_withdraw_cookie(cookie); + } else { + fscache_set_cookie_state(cookie, FSCACHE_COOKIE_STATE_DROPPED); + fscache_unhash_cookie(cookie); + } fscache_put_cookie(cookie, fscache_cookie_put_relinquish); } EXPORT_SYMBOL(__fscache_relinquish_cookie); diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h index 936ef731bbc7..ae6a75976450 100644 --- a/include/linux/fscache-cache.h +++ b/include/linux/fscache-cache.h @@ -57,6 +57,15 @@ 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); }; extern struct workqueue_struct *fscache_wq; @@ -72,6 +81,7 @@ extern int fscache_add_cache(struct fscache_cache *cache, void *cache_priv); extern void fscache_withdraw_cache(struct fscache_cache *cache); extern void fscache_withdraw_volume(struct fscache_volume *volume); +extern void fscache_withdraw_cookie(struct fscache_cookie *cookie); extern void fscache_io_error(struct fscache_cache *cache); @@ -85,8 +95,21 @@ extern void fscache_put_cookie(struct fscache_cookie *cookie, enum fscache_cookie_trace where); extern void fscache_end_cookie_access(struct fscache_cookie *cookie, enum fscache_access_trace why); -extern void fscache_set_cookie_state(struct fscache_cookie *cookie, - enum fscache_cookie_state state); +extern void fscache_cookie_lookup_negative(struct fscache_cookie *cookie); +extern void fscache_caching_failed(struct fscache_cookie *cookie); + +/** + * fscache_cookie_state - Read the state of a cookie + * @cookie: The cookie to query + * + * Get the state of a cookie, imposing an ordering between the cookie contents + * and the state value. Paired with fscache_set_cookie_state(). + */ +static inline +enum fscache_cookie_state fscache_cookie_state(struct fscache_cookie *cookie) +{ + return smp_load_acquire(&cookie->state); +} /** * fscache_get_key - Get a pointer to the cookie key diff --git a/include/linux/fscache.h b/include/linux/fscache.h index e25e1b8bb91b..0568414bd392 100644 --- a/include/linux/fscache.h +++ b/include/linux/fscache.h @@ -111,7 +111,7 @@ struct fscache_cookie { #define FSCACHE_COOKIE_NACC_ELEVATED 8 /* T if n_accesses is incremented */ #define FSCACHE_COOKIE_DO_RELINQUISH 9 /* T if this cookie needs relinquishment */ #define FSCACHE_COOKIE_DO_WITHDRAW 10 /* T if this cookie needs withdrawing */ -#define FSCACHE_COOKIE_DO_COMMIT 11 /* T if this cookie needs committing */ +#define FSCACHE_COOKIE_DO_LRU_DISCARD 11 /* T if this cookie needs LRU discard */ #define FSCACHE_COOKIE_DO_PREP_TO_WRITE 12 /* T if cookie needs write preparation */ #define FSCACHE_COOKIE_HAVE_DATA 13 /* T if this cookie has data stored */ diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h index c16b2ca4bf3f..8b3594de9d2c 100644 --- a/include/trace/events/fscache.h +++ b/include/trace/events/fscache.h @@ -68,6 +68,8 @@ enum fscache_access_trace { fscache_access_acquire_volume_end, fscache_access_cache_pin, fscache_access_cache_unpin, + fscache_access_lookup_cookie_end, + fscache_access_lookup_cookie_end_failed, fscache_access_relinquish_volume, fscache_access_relinquish_volume_end, fscache_access_unlive, @@ -124,6 +126,8 @@ 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_lookup_cookie_end_failed,"END lookupf") \ EM(fscache_access_relinquish_volume, "BEGIN rlq_vol") \ EM(fscache_access_relinquish_volume_end,"END rlq_vol") \ E_(fscache_access_unlive, "END unlive ")

[17/64] fscache: Implement simple cookie state machine

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