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 Subject: [PATCH 11/64] fscache: Implement cache-level access helpers Date: Mon, 29 Nov 2021 14:25:32 +0000 [thread overview] Message-ID: <163819593239.215744.7537428720603638088.stgit@warthog.procyon.org.uk> (raw) In-Reply-To: <163819575444.215744.318477214576928110.stgit@warthog.procyon.org.uk> Add a pair of functions to pin/unpin a cache that we're wanting to do a high-level access to (such as creating or removing a volume): bool fscache_begin_cache_access(struct fscache_cache *cache, enum fscache_access_trace why); void fscache_end_cache_access(struct fscache_cache *cache, enum fscache_access_trace why); The way the access gate works/will work is: (1) If the cache tests as not live (state is not FSCACHE_CACHE_IS_ACTIVE), then we return false to indicate access was not permitted. (2) If the cache tests as live, then we increment the n_accesses count and then recheck the liveness, ending the access if it ceased to be live. (3) When we end the access, we decrement n_accesses and wake up the any waiters if it reaches 0. (4) Whilst the cache is caching, n_accesses is kept artificially incremented to prevent wakeups from happening. (5) When the cache is taken offline, the state is changed to prevent new accesses, n_accesses is decremented and we wait for n_accesses to become 0. Note that some of this is implemented in a later patch. Signed-off-by: David Howells <dhowells@redhat.com> cc: linux-cachefs@redhat.com --- fs/fscache/cache.c | 62 ++++++++++++++++++++++++++++++++++++++++ fs/fscache/internal.h | 2 + fs/fscache/main.c | 2 + include/trace/events/fscache.h | 41 ++++++++++++++++++++++++++ 4 files changed, 107 insertions(+) diff --git a/fs/fscache/cache.c b/fs/fscache/cache.c index 8db77bb9f8e2..e867cff53a70 100644 --- a/fs/fscache/cache.c +++ b/fs/fscache/cache.c @@ -216,6 +216,68 @@ void fscache_relinquish_cache(struct fscache_cache *cache) } EXPORT_SYMBOL(fscache_relinquish_cache); +/** + * fscache_begin_cache_access - Pin a cache so it can be accessed + * @cache: The cache-level cookie + * @why: An indication of the circumstances of the access for tracing + * + * Attempt to pin the cache to prevent it from going away whilst we're + * accessing it and returns true if successful. This works as follows: + * + * (1) If the cache tests as not live (state is not FSCACHE_CACHE_IS_ACTIVE), + * then we return false to indicate access was not permitted. + * + * (2) If the cache tests as live, then we increment the n_accesses count and + * then recheck the liveness, ending the access if it ceased to be live. + * + * (3) When we end the access, we decrement n_accesses and wake up the any + * waiters if it reaches 0. + * + * (4) Whilst the cache is caching, n_accesses is kept artificially + * incremented to prevent wakeups from happening. + * + * (5) When the cache is taken offline, the state is changed to prevent new + * accesses, n_accesses is decremented and we wait for n_accesses to + * become 0. + */ +bool fscache_begin_cache_access(struct fscache_cache *cache, enum fscache_access_trace why) +{ + int n_accesses; + + if (!fscache_cache_is_live(cache)) + return false; + + n_accesses = atomic_inc_return(&cache->n_accesses); + smp_mb__after_atomic(); /* Reread live flag after n_accesses */ + trace_fscache_access_cache(cache->debug_id, refcount_read(&cache->ref), + n_accesses, why); + if (!fscache_cache_is_live(cache)) { + fscache_end_cache_access(cache, fscache_access_unlive); + return false; + } + return true; +} + +/** + * fscache_end_cache_access - Unpin a cache at the end of an access. + * @cache: The cache-level cookie + * @why: An indication of the circumstances of the access for tracing + * + * Unpin a cache after we've accessed it. The @why indicator is merely + * provided for tracing purposes. + */ +void fscache_end_cache_access(struct fscache_cache *cache, enum fscache_access_trace why) +{ + int n_accesses; + + smp_mb__before_atomic(); + n_accesses = atomic_dec_return(&cache->n_accesses); + trace_fscache_access_cache(cache->debug_id, refcount_read(&cache->ref), + n_accesses, why); + if (n_accesses == 0) + wake_up_var(&cache->n_accesses); +} + #ifdef CONFIG_PROC_FS static const char fscache_cache_states[NR__FSCACHE_CACHE_STATE] = "-PAEW"; diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h index c9bd4bcd4485..ca035d6be7f9 100644 --- a/fs/fscache/internal.h +++ b/fs/fscache/internal.h @@ -23,6 +23,8 @@ #ifdef CONFIG_PROC_FS extern const struct seq_operations fscache_caches_seq_ops; #endif +bool fscache_begin_cache_access(struct fscache_cache *cache, enum fscache_access_trace why); +void fscache_end_cache_access(struct fscache_cache *cache, enum fscache_access_trace why); struct fscache_cache *fscache_lookup_cache(const char *name, bool is_cache); void fscache_put_cache(struct fscache_cache *cache, enum fscache_cache_trace where); diff --git a/fs/fscache/main.c b/fs/fscache/main.c index fad9c1933987..e1f14b29cff4 100644 --- a/fs/fscache/main.c +++ b/fs/fscache/main.c @@ -21,6 +21,8 @@ module_param_named(debug, fscache_debug, uint, MODULE_PARM_DESC(fscache_debug, "FS-Cache debugging mask"); +EXPORT_TRACEPOINT_SYMBOL(fscache_access_cache); + struct workqueue_struct *fscache_wq; EXPORT_SYMBOL(fscache_wq); diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h index 5121d1fb8ff2..0ce0bd88e2b4 100644 --- a/include/trace/events/fscache.h +++ b/include/trace/events/fscache.h @@ -62,6 +62,12 @@ enum fscache_cookie_trace { fscache_cookie_see_work, }; +enum fscache_access_trace { + fscache_access_cache_pin, + fscache_access_cache_unpin, + fscache_access_unlive, +}; + #endif /* @@ -107,6 +113,11 @@ enum fscache_cookie_trace { EM(fscache_cookie_see_withdraw, "- x-wth") \ E_(fscache_cookie_see_work, "- work ") +#define fscache_access_traces \ + EM(fscache_access_cache_pin, "PIN cache ") \ + EM(fscache_access_cache_unpin, "UNPIN cache ") \ + E_(fscache_access_unlive, "END unlive ") + /* * Export enum symbols via userspace. */ @@ -118,6 +129,7 @@ enum fscache_cookie_trace { fscache_cache_traces; fscache_volume_traces; fscache_cookie_traces; +fscache_access_traces; /* * Now redefine the EM() and E_() macros to map the enums to the strings that @@ -204,6 +216,35 @@ TRACE_EVENT(fscache_cookie, __entry->ref) ); +TRACE_EVENT(fscache_access_cache, + TP_PROTO(unsigned int cache_debug_id, + int ref, + int n_accesses, + enum fscache_access_trace why), + + TP_ARGS(cache_debug_id, ref, n_accesses, why), + + TP_STRUCT__entry( + __field(unsigned int, cache ) + __field(int, ref ) + __field(int, n_accesses ) + __field(enum fscache_access_trace, why ) + ), + + TP_fast_assign( + __entry->cache = cache_debug_id; + __entry->ref = ref; + __entry->n_accesses = n_accesses; + __entry->why = why; + ), + + TP_printk("C=%08x %s r=%d a=%d", + __entry->cache, + __print_symbolic(__entry->why, fscache_access_traces), + __entry->ref, + __entry->n_accesses) + ); + TRACE_EVENT(fscache_acquire, TP_PROTO(struct fscache_cookie *cookie),
next prev parent reply other threads:[~2021-11-29 14:27 UTC|newest] Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-11-29 14:22 [PATCH 00/64] fscache, cachefiles: Rewrite David Howells 2021-11-29 14:22 ` [PATCH 01/64] fscache, cachefiles: Disable configuration David Howells 2021-11-29 14:22 ` [PATCH 02/64] cachefiles: Delete the cachefiles driver pending rewrite David Howells 2021-11-29 14:23 ` [PATCH 03/64] fscache: Remove the contents of the fscache driver, " David Howells 2021-11-29 14:23 ` [PATCH 04/64] netfs: Display the netfs inode number in the netfs_read tracepoint David Howells 2021-11-29 14:23 ` [PATCH 05/64] netfs: Pass a flag to ->prepare_write() to say if there's no alloc'd space David Howells 2021-11-29 14:24 ` [PATCH 06/64] fscache: Introduce new driver David Howells 2021-11-29 14:24 ` [PATCH 07/64] fscache: Implement a hash function David Howells 2021-11-29 14:24 ` [PATCH 08/64] fscache: Implement cache registration David Howells 2021-11-29 14:24 ` [PATCH 09/64] fscache: Implement volume registration David Howells 2021-11-29 14:25 ` [PATCH 10/64] fscache: Implement cookie registration David Howells 2021-11-29 14:25 ` David Howells [this message] 2021-11-29 14:25 ` [PATCH 12/64] fscache: Implement volume-level access helpers David Howells 2021-11-29 14:25 ` [PATCH 13/64] fscache: Implement cookie-level " David Howells 2021-11-29 14:26 ` [PATCH 14/64] fscache: Implement functions add/remove a cache David Howells 2021-11-29 14:26 ` [PATCH 15/64] fscache: Provide and use cache methods to lookup/create/free a volume David Howells 2021-11-29 14:26 ` [PATCH 16/64] fscache: Add a function for a cache backend to note an I/O error David Howells 2021-11-29 14:26 ` [PATCH 17/64] fscache: Implement simple cookie state machine David Howells 2021-11-29 14:26 ` [PATCH 18/64] fscache: Implement cookie user counting and resource pinning David Howells 2021-11-29 14:27 ` [PATCH 19/64] fscache: Implement cookie invalidation David Howells 2021-11-29 14:27 ` [PATCH 20/64] fscache: Provide a means to begin an operation David Howells 2021-11-29 14:28 ` [PATCH 21/64] fscache: Count data storage objects in a cache David Howells 2021-11-29 14:28 ` [PATCH 22/64] fscache: Provide read/write stat counters for the cache David Howells 2021-11-29 14:28 ` [PATCH 23/64] fscache: Provide a function to let the netfs update its coherency data David Howells 2021-11-29 14:28 ` [PATCH 24/64] netfs: Pass more information on how to deal with a hole in the cache David Howells 2021-12-06 11:42 ` JeffleXu 2021-12-09 16:49 ` David Howells 2021-11-29 14:28 ` [PATCH 25/64] fscache: Implement raw I/O interface David Howells 2021-11-29 14:29 ` [PATCH 26/64] fscache: Implement higher-level write " David Howells 2021-11-29 14:29 ` [PATCH 27/64] vfs, fscache: Implement pinning of cache usage for writeback David Howells 2021-11-29 14:29 ` [PATCH 28/64] fscache: Provide a function to note the release of a page David Howells 2021-11-29 14:30 ` [PATCH 29/64] fscache: Provide a function to resize a cookie David Howells 2021-11-29 14:30 ` [PATCH 30/64] cachefiles: Introduce rewritten driver David Howells 2021-11-29 14:30 ` [PATCH 31/64] cachefiles: Define structs David Howells 2021-11-29 14:30 ` [PATCH 32/64] cachefiles: Add some error injection support David Howells 2021-11-29 14:30 ` [PATCH 33/64] cachefiles: Add a couple of tracepoints for logging errors David Howells 2021-11-29 14:31 ` [PATCH 34/64] cachefiles: Add cache error reporting macro David Howells 2021-11-29 14:31 ` [PATCH 35/64] cachefiles: Add security derivation David Howells 2021-11-29 14:31 ` [PATCH 36/64] cachefiles: Register a miscdev and parse commands over it David Howells 2021-11-29 14:31 ` [PATCH 37/64] cachefiles: Provide a function to check how much space there is David Howells 2021-11-29 14:31 ` [PATCH 38/64] vfs, cachefiles: Mark a backing file in use with an inode flag David Howells 2021-11-29 14:31 ` [PATCH 39/64] cachefiles: Implement a function to get/create a directory in the cache David Howells 2021-11-29 14:32 ` [PATCH 40/64] cachefiles: Implement cache registration and withdrawal David Howells 2021-11-29 14:32 ` [PATCH 41/64] cachefiles: Implement volume support David Howells 2021-11-29 14:33 ` [PATCH 42/64] cachefiles: Add tracepoints for calls to the VFS David Howells 2021-11-29 14:33 ` [PATCH 43/64] cachefiles: Implement object lifecycle funcs David Howells 2021-11-29 14:33 ` [PATCH 44/64] cachefiles: Implement key to filename encoding David Howells 2021-12-01 5:46 ` JeffleXu 2021-12-01 8:29 ` David Howells 2021-11-29 14:33 ` [PATCH 45/64] cachefiles: Implement metadata/coherency data storage in xattrs David Howells 2021-11-29 14:33 ` [PATCH 46/64] cachefiles: Mark a backing file in use with an inode flag David Howells 2021-11-29 14:33 ` [PATCH 47/64] cachefiles: Implement culling daemon commands David Howells 2021-11-29 14:34 ` [PATCH 48/64] cachefiles: Implement backing file wrangling David Howells 2021-11-29 14:34 ` [PATCH 49/64] cachefiles: Implement begin and end I/O operation David Howells 2021-11-29 14:34 ` [PATCH 50/64] cachefiles: Implement cookie resize for truncate David Howells 2021-11-29 14:34 ` [PATCH 51/64] cachefiles: Implement the I/O routines David Howells 2021-11-30 16:15 ` Nathan Chancellor 2021-11-30 21:05 ` David Howells 2021-11-29 14:34 ` [PATCH 52/64] cachefiles: Allow cachefiles to actually function David Howells 2021-11-29 14:35 ` [PATCH 53/64] fscache, cachefiles: Display stats of no-space events David Howells 2021-11-29 14:35 ` [PATCH 54/64] fscache, cachefiles: Display stat of culling events David Howells 2021-11-29 14:36 ` [PATCH 55/64] afs: Handle len being extending over page end in write_begin/write_end David Howells 2021-11-29 14:36 ` [PATCH 56/64] afs: Fix afs_write_end() to handle len > page size David Howells 2021-11-29 14:36 ` [PATCH 57/64] afs: Convert afs to use the new fscache API David Howells 2021-11-29 14:37 ` [PATCH 58/64] afs: Copy local writes to the cache when writing to the server David Howells 2021-11-29 14:37 ` [PATCH 59/64] afs: Skip truncation on the server of data we haven't written yet David Howells 2021-11-29 14:37 ` [PATCH 60/64] 9p: Use fscache indexing rewrite and reenable caching David Howells 2021-11-29 14:37 ` [PATCH 61/64] 9p: Copy local writes to the cache when writing to the server David Howells 2021-11-29 14:38 ` [PATCH 62/64] nfs: Convert to new fscache volume/cookie API David Howells 2021-11-29 14:38 ` [PATCH 63/64] cifs: Support fscache indexing rewrite (untested) David Howells 2021-11-29 14:38 ` [PATCH 64/64] fscache: Rewrite documentation David Howells 2021-11-29 18:12 ` [PATCH 00/64] fscache, cachefiles: Rewrite Linus Torvalds 2021-11-29 21:40 ` [PATCH 35/64] cachefiles: Add security derivation David Howells
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