Provide a pair of functions to count the number of users of a cookie (open files, writeback, invalidation, resizing, reads, writes) and to pin cache resources for the whilst there are users. The first function gets a usage on a cookie: void fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify); The caller should indicate the cookie to use and whether or not the caller is in a context that may modify the cookie (e.g. a file open O_RDWR). If not already open, this will trigger lookup and/or creation of the backing store in the background and resources may be pinned to the cookie by the cache. The second function drops a usage on a cookie and, optionally, updates the coherency data: void fscache_unuse_cookie(struct fscache_cookie *cookie, const void *aux_data, const loff_t *object_size); If non-NULL, the aux_data buffer and/or the object_size will be saved into the cookie and will be set on the backing store when the object is committed. If this removes the last usage on a cookie, the cookie is placed onto an LRU list from which it will be removed and closed after a couple of seconds if it doesn't get reused. This prevents resource overload in the cache - in particular it prevents it from holding too many files open. Changes ======= ver #2: - Fix fscache_unuse_cookie() to use atomic_dec_and_lock() to avoid a potential race if the cookie gets reused before it completes the unusement. Signed-off-by: David Howells <dhowells@xxxxxxxxxx> cc: linux-cachefs@xxxxxxxxxx --- fs/fscache/cookie.c | 207 ++++++++++++++++++++++++++++++++++++++++ fs/fscache/internal.h | 5 + fs/fscache/stats.c | 12 ++ include/linux/fscache-cache.h | 14 +++ include/linux/fscache.h | 82 ++++++++++++++++ include/trace/events/fscache.h | 12 ++ 6 files changed, 331 insertions(+), 1 deletion(-) diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c index b7373ebcaf56..cf987756534c 100644 --- a/fs/fscache/cookie.c +++ b/fs/fscache/cookie.c @@ -15,6 +15,8 @@ struct kmem_cache *fscache_cookie_jar; +static void fscache_cookie_lru_timed_out(struct timer_list *timer); +static void fscache_cookie_lru_worker(struct work_struct *work); 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); @@ -23,7 +25,12 @@ static void fscache_lookup_cookie(struct fscache_cookie *cookie); static struct hlist_bl_head fscache_cookie_hash[1 << fscache_cookie_hash_shift]; static LIST_HEAD(fscache_cookies); static DEFINE_RWLOCK(fscache_cookies_lock); -static const char fscache_cookie_stages[FSCACHE_COOKIE_STAGE__NR] = "-LCAFWRD"; +static LIST_HEAD(fscache_cookie_lru); +static DEFINE_SPINLOCK(fscache_cookie_lru_lock); +DEFINE_TIMER(fscache_cookie_lru_timer, fscache_cookie_lru_timed_out); +static DECLARE_WORK(fscache_cookie_lru_work, fscache_cookie_lru_worker); +static const char fscache_cookie_stages[FSCACHE_COOKIE_STAGE__NR] = "-LCAFMWRD"; +unsigned int fscache_lru_cookie_timeout = 10 * HZ; void fscache_print_cookie(struct fscache_cookie *cookie, char prefix) { @@ -48,6 +55,13 @@ void fscache_print_cookie(struct fscache_cookie *cookie, char prefix) static void fscache_free_cookie(struct fscache_cookie *cookie) { + if (WARN_ON_ONCE(!list_empty(&cookie->commit_link))) { + spin_lock(&fscache_cookie_lru_lock); + list_del_init(&cookie->commit_link); + spin_unlock(&fscache_cookie_lru_lock); + fscache_stat_d(&fscache_n_cookies_lru); + fscache_stat(&fscache_n_cookies_lru_removed); + } write_lock(&fscache_cookies_lock); list_del(&cookie->proc_link); write_unlock(&fscache_cookies_lock); @@ -442,6 +456,122 @@ static void fscache_lookup_cookie(struct fscache_cookie *cookie) fscache_end_volume_access(cookie->volume, fscache_access_lookup_cookie_end); } +/* + * Start using the cookie for I/O. This prevents the backing object from being + * reaped by VM pressure. + */ +void __fscache_use_cookie(struct fscache_cookie *cookie, bool will_modify) +{ + enum fscache_cookie_stage stage; + bool changed_stage = false, queue = false; + + _enter("c=%08x", cookie->debug_id); + + if (WARN(test_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags), + "Trying to use relinquished cookie\n")) + return; + + spin_lock(&cookie->lock); + + atomic_inc(&cookie->n_active); + +again: + stage = cookie->stage; + switch (stage) { + case FSCACHE_COOKIE_STAGE_QUIESCENT: + if (will_modify) { + set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags); + set_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags); + } + if (!fscache_begin_volume_access(cookie->volume, + fscache_access_lookup_cookie)) + break; + + __fscache_begin_cookie_access(cookie, fscache_access_lookup_cookie); + __fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_LOOKING_UP); + smp_mb__before_atomic(); /* Set stage before is-caching + * vs __fscache_begin_cookie_access() + */ + set_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags); + set_bit(FSCACHE_COOKIE_HAS_BEEN_CACHED, &cookie->flags); + changed_stage = true; + queue = true; + break; + + case FSCACHE_COOKIE_STAGE_LOOKING_UP: + case FSCACHE_COOKIE_STAGE_CREATING: + if (will_modify) + set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags); + break; + case FSCACHE_COOKIE_STAGE_ACTIVE: + if (will_modify && + !test_and_set_bit(FSCACHE_COOKIE_LOCAL_WRITE, &cookie->flags)) { + set_bit(FSCACHE_COOKIE_DO_PREP_TO_WRITE, &cookie->flags); + queue = true; + } + break; + + case FSCACHE_COOKIE_STAGE_FAILED: + case FSCACHE_COOKIE_STAGE_WITHDRAWING: + break; + + case FSCACHE_COOKIE_STAGE_COMMITTING: + spin_unlock(&cookie->lock); + wait_var_event(&cookie->stage, + READ_ONCE(cookie->stage) != FSCACHE_COOKIE_STAGE_COMMITTING); + spin_lock(&cookie->lock); + goto again; + + case FSCACHE_COOKIE_STAGE_DROPPED: + case FSCACHE_COOKIE_STAGE_RELINQUISHING: + WARN(1, "Can't use cookie in stage %u\n", cookie->stage); + break; + } + + spin_unlock(&cookie->lock); + if (changed_stage) + wake_up_cookie_stage(cookie); + if (queue) + fscache_queue_cookie(cookie, fscache_cookie_get_use_work); + _leave(""); +} +EXPORT_SYMBOL(__fscache_use_cookie); + +static void fscache_unuse_cookie_locked(struct fscache_cookie *cookie) +{ + clear_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags); + if (!test_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags)) + return; + + cookie->unused_at = jiffies; + spin_lock(&fscache_cookie_lru_lock); + if (list_empty(&cookie->commit_link)) { + fscache_get_cookie(cookie, fscache_cookie_get_lru); + fscache_stat(&fscache_n_cookies_lru); + } + list_move_tail(&cookie->commit_link, &fscache_cookie_lru); + + spin_unlock(&fscache_cookie_lru_lock); + timer_reduce(&fscache_cookie_lru_timer, + jiffies + fscache_lru_cookie_timeout); +} + +/* + * Stop using the cookie for I/O. + */ +void __fscache_unuse_cookie(struct fscache_cookie *cookie, + const void *aux_data, const loff_t *object_size) +{ + if (aux_data || object_size) + __fscache_update_cookie(cookie, aux_data, object_size); + + if (atomic_dec_and_lock(&cookie->n_active, &cookie->lock)) { + fscache_unuse_cookie_locked(cookie); + spin_unlock(&cookie->lock); + } +} +EXPORT_SYMBOL(__fscache_unuse_cookie); + /* * Perform work upon the cookie, such as committing its cache state, * relinquishing it or withdrawing the backing cache. We're protected from the @@ -471,6 +601,7 @@ static void __fscache_cookie_worker(struct fscache_cookie *cookie) case FSCACHE_COOKIE_STAGE_FAILED: break; + case FSCACHE_COOKIE_STAGE_COMMITTING: case FSCACHE_COOKIE_STAGE_RELINQUISHING: case FSCACHE_COOKIE_STAGE_WITHDRAWING: if (test_and_clear_bit(FSCACHE_COOKIE_IS_CACHING, &cookie->flags) && @@ -480,6 +611,8 @@ static void __fscache_cookie_worker(struct fscache_cookie *cookie) fscache_see_cookie(cookie, fscache_cookie_see_relinquish); fscache_drop_cookie(cookie); break; + } else if (cookie->stage == FSCACHE_COOKIE_STAGE_COMMITTING) { + fscache_see_cookie(cookie, fscache_cookie_see_committing); } else { fscache_see_cookie(cookie, fscache_cookie_see_withdraw); } @@ -519,6 +652,77 @@ static void __fscache_withdraw_cookie(struct fscache_cookie *cookie) __fscache_end_cookie_access(cookie); } +static void fscache_cookie_lru_do_one(struct fscache_cookie *cookie) +{ + fscache_see_cookie(cookie, fscache_cookie_see_lru_do_one); + + spin_lock(&cookie->lock); + if (cookie->stage != FSCACHE_COOKIE_STAGE_ACTIVE || + time_before(jiffies, cookie->unused_at + fscache_lru_cookie_timeout) || + atomic_read(&cookie->n_active) > 0) { + spin_unlock(&cookie->lock); + fscache_stat(&fscache_n_cookies_lru_removed); + } else { + __fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_COMMITTING); + set_bit(FSCACHE_COOKIE_DO_COMMIT, &cookie->flags); + spin_unlock(&cookie->lock); + fscache_stat(&fscache_n_cookies_lru_expired); + _debug("lru c=%x", cookie->debug_id); + __fscache_withdraw_cookie(cookie); + } + + fscache_put_cookie(cookie, fscache_cookie_put_lru); +} + +static void fscache_cookie_lru_worker(struct work_struct *work) +{ + struct fscache_cookie *cookie; + unsigned long unused_at; + + spin_lock(&fscache_cookie_lru_lock); + + while (!list_empty(&fscache_cookie_lru)) { + cookie = list_first_entry(&fscache_cookie_lru, + struct fscache_cookie, commit_link); + unused_at = cookie->unused_at + fscache_lru_cookie_timeout; + if (time_before(jiffies, unused_at)) { + timer_reduce(&fscache_cookie_lru_timer, unused_at); + break; + } + + list_del_init(&cookie->commit_link); + fscache_stat_d(&fscache_n_cookies_lru); + spin_unlock(&fscache_cookie_lru_lock); + fscache_cookie_lru_do_one(cookie); + spin_lock(&fscache_cookie_lru_lock); + } + + spin_unlock(&fscache_cookie_lru_lock); +} + +static void fscache_cookie_lru_timed_out(struct timer_list *timer) +{ + queue_work(fscache_wq, &fscache_cookie_lru_work); +} + +static void fscache_cookie_drop_from_lru(struct fscache_cookie *cookie) +{ + bool need_put = false; + + if (!list_empty(&cookie->commit_link)) { + spin_lock(&fscache_cookie_lru_lock); + if (!list_empty(&cookie->commit_link)) { + list_del_init(&cookie->commit_link); + fscache_stat_d(&fscache_n_cookies_lru); + fscache_stat(&fscache_n_cookies_lru_dropped); + need_put = true; + } + spin_unlock(&fscache_cookie_lru_lock); + if (need_put) + fscache_put_cookie(cookie, fscache_cookie_put_lru); + } +} + /* * Remove a cookie from the hash table. */ @@ -551,6 +755,7 @@ static void fscache_drop_cookie(struct fscache_cookie *cookie) static void fscache_drop_withdraw_cookie(struct fscache_cookie *cookie) { + fscache_cookie_drop_from_lru(cookie); __fscache_withdraw_cookie(cookie); } diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h index 5669ba4bc8a9..5aff9c143616 100644 --- a/fs/fscache/internal.h +++ b/fs/fscache/internal.h @@ -32,6 +32,7 @@ struct fscache_cache *fscache_lookup_cache(const char *name, bool is_cache); */ extern struct kmem_cache *fscache_cookie_jar; extern const struct seq_operations fscache_cookies_seq_ops; +extern struct timer_list fscache_cookie_lru_timer; extern void fscache_print_cookie(struct fscache_cookie *cookie, char prefix); extern bool fscache_begin_cookie_access(struct fscache_cookie *cookie, @@ -70,6 +71,10 @@ extern atomic_t fscache_n_volumes; extern atomic_t fscache_n_volumes_collision; extern atomic_t fscache_n_volumes_nomem; extern atomic_t fscache_n_cookies; +extern atomic_t fscache_n_cookies_lru; +extern atomic_t fscache_n_cookies_lru_expired; +extern atomic_t fscache_n_cookies_lru_removed; +extern atomic_t fscache_n_cookies_lru_dropped; extern atomic_t fscache_n_acquires; extern atomic_t fscache_n_acquires_null; diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c index fd2bd08c1ecb..17bf57374595 100644 --- a/fs/fscache/stats.c +++ b/fs/fscache/stats.c @@ -17,6 +17,10 @@ atomic_t fscache_n_volumes; atomic_t fscache_n_volumes_collision; atomic_t fscache_n_volumes_nomem; atomic_t fscache_n_cookies; +atomic_t fscache_n_cookies_lru; +atomic_t fscache_n_cookies_lru_expired; +atomic_t fscache_n_cookies_lru_removed; +atomic_t fscache_n_cookies_lru_dropped; atomic_t fscache_n_acquires; atomic_t fscache_n_acquires_null; @@ -51,6 +55,14 @@ int fscache_stats_show(struct seq_file *m, void *v) atomic_read(&fscache_n_acquires_ok), atomic_read(&fscache_n_acquires_oom)); + seq_printf(m, "LRU : n=%u exp=%u rmv=%u drp=%u at=%ld\n", + atomic_read(&fscache_n_cookies_lru), + atomic_read(&fscache_n_cookies_lru_expired), + atomic_read(&fscache_n_cookies_lru_removed), + atomic_read(&fscache_n_cookies_lru_dropped), + timer_pending(&fscache_cookie_lru_timer) ? + fscache_cookie_lru_timer.expires - jiffies : 0); + seq_printf(m, "Updates: n=%u\n", atomic_read(&fscache_n_updates)); diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h index f6d63dc0ffa9..a67c29207ad5 100644 --- a/include/linux/fscache-cache.h +++ b/include/linux/fscache-cache.h @@ -132,6 +132,20 @@ static inline void *fscache_get_key(struct fscache_cookie *cookie) return cookie->key; } +/** + * 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. + */ +static inline void fscache_cookie_lookup_negative(struct fscache_cookie *cookie) +{ + set_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags); + fscache_set_cookie_stage(cookie, FSCACHE_COOKIE_STAGE_CREATING); +} + extern struct workqueue_struct *fscache_wq; #endif /* _LINUX_FSCACHE_CACHE_H */ diff --git a/include/linux/fscache.h b/include/linux/fscache.h index ebdc0fd1f309..df985507fa5e 100644 --- a/include/linux/fscache.h +++ b/include/linux/fscache.h @@ -27,11 +27,15 @@ #define fscache_available() (1) #define fscache_volume_valid(volume) (volume) #define fscache_cookie_valid(cookie) (cookie) +#define fscache_resources_valid(cres) ((cres)->cache_priv) +#define fscache_cookie_enabled(cookie) (cookie && !test_bit(FSCACHE_COOKIE_DISABLED, &cookie->flags)) #else #define __fscache_available (0) #define fscache_available() (0) #define fscache_volume_valid(volume) (0) #define fscache_cookie_valid(cookie) (0) +#define fscache_resources_valid(cres) (false) +#define fscache_cookie_enabled(cookie) (0) #endif struct fscache_cookie; @@ -50,6 +54,7 @@ enum fscache_cookie_stage { FSCACHE_COOKIE_STAGE_CREATING, /* The cache object is being created */ FSCACHE_COOKIE_STAGE_ACTIVE, /* The cache is active, readable and writable */ FSCACHE_COOKIE_STAGE_FAILED, /* The cache failed, withdraw to clear */ + FSCACHE_COOKIE_STAGE_COMMITTING, /* The cookie is being committed */ FSCACHE_COOKIE_STAGE_WITHDRAWING, /* The cookie is being withdrawn */ FSCACHE_COOKIE_STAGE_RELINQUISHING, /* The cookie is being relinquished */ FSCACHE_COOKIE_STAGE_DROPPED, /* The cookie has been dropped */ @@ -150,6 +155,8 @@ extern struct fscache_cookie *__fscache_acquire_cookie( const void *, size_t, const void *, size_t, loff_t); +extern void __fscache_use_cookie(struct fscache_cookie *, bool); +extern void __fscache_unuse_cookie(struct fscache_cookie *, const void *, const loff_t *); extern void __fscache_relinquish_cookie(struct fscache_cookie *, bool); /** @@ -224,6 +231,39 @@ struct fscache_cookie *fscache_acquire_cookie(struct fscache_volume *volume, object_size); } +/** + * fscache_use_cookie - Request usage of cookie attached to an object + * @object: Object description + * @will_modify: If cache is expected to be modified locally + * + * Request usage of the cookie attached to an object. The caller should tell + * the cache if the object's contents are about to be modified locally and then + * the cache can apply the policy that has been set to handle this case. + */ +static inline void fscache_use_cookie(struct fscache_cookie *cookie, + bool will_modify) +{ + if (fscache_cookie_valid(cookie)) + __fscache_use_cookie(cookie, will_modify); +} + +/** + * fscache_unuse_cookie - Cease usage of cookie attached to an object + * @object: Object description + * @aux_data: Updated auxiliary data (or NULL) + * @object_size: Revised size of the object (or NULL) + * + * Cease usage of the cookie attached to an object. When the users count + * reaches zero then the cookie relinquishment will be permitted to proceed. + */ +static inline void fscache_unuse_cookie(struct fscache_cookie *cookie, + const void *aux_data, + const loff_t *object_size) +{ + if (fscache_cookie_valid(cookie)) + __fscache_unuse_cookie(cookie, aux_data, object_size); +} + /** * fscache_relinquish_cookie - Return the cookie to the cache, maybe discarding * it @@ -243,4 +283,46 @@ void fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire) __fscache_relinquish_cookie(cookie, retire); } +/* + * Find the auxiliary data on a cookie. + */ +static inline void *fscache_get_aux(struct fscache_cookie *cookie) +{ + if (cookie->aux_len <= sizeof(cookie->inline_aux)) + return cookie->inline_aux; + else + return cookie->aux; +} + +/* + * Update the auxiliary data on a cookie. + */ +static inline +void fscache_update_aux(struct fscache_cookie *cookie, + const void *aux_data, const loff_t *object_size) +{ + void *p = fscache_get_aux(cookie); + + if (aux_data && p) + memcpy(p, aux_data, cookie->aux_len); + if (object_size) + cookie->object_size = *object_size; +} + +#ifdef CONFIG_FSCACHE_STATS +extern atomic_t fscache_n_updates; +#endif + +static inline +void __fscache_update_cookie(struct fscache_cookie *cookie, const void *aux_data, + const loff_t *object_size) +{ +#ifdef CONFIG_FSCACHE_STATS + atomic_inc(&fscache_n_updates); +#endif + fscache_update_aux(cookie, aux_data, object_size); + smp_wmb(); + set_bit(FSCACHE_COOKIE_NEEDS_UPDATE, &cookie->flags); +} + #endif /* _LINUX_FSCACHE_H */ diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h index 00ffe0f8e6d3..2b31ef34efa2 100644 --- a/include/trace/events/fscache.h +++ b/include/trace/events/fscache.h @@ -50,13 +50,18 @@ enum fscache_cookie_trace { fscache_cookie_discard, fscache_cookie_get_end_access, fscache_cookie_get_hash_collision, + fscache_cookie_get_lru, + fscache_cookie_get_use_work, fscache_cookie_new_acquire, fscache_cookie_put_hash_collision, + fscache_cookie_put_lru, fscache_cookie_put_over_queued, fscache_cookie_put_relinquish, fscache_cookie_put_withdrawn, fscache_cookie_put_work, fscache_cookie_see_active, + fscache_cookie_see_lru_do_one, + fscache_cookie_see_committing, fscache_cookie_see_relinquish, fscache_cookie_see_withdraw, fscache_cookie_see_work, @@ -67,6 +72,7 @@ enum fscache_access_trace { fscache_access_acquire_volume_end, fscache_access_cache_pin, fscache_access_cache_unpin, + fscache_access_lookup_cookie, fscache_access_lookup_cookie_end, fscache_access_relinquish_volume, fscache_access_relinquish_volume_end, @@ -107,13 +113,18 @@ enum fscache_access_trace { EM(fscache_cookie_discard, "DISCARD ") \ EM(fscache_cookie_get_hash_collision, "GET hcoll") \ EM(fscache_cookie_get_end_access, "GQ endac") \ + EM(fscache_cookie_get_lru, "GET lru ") \ + EM(fscache_cookie_get_use_work, "GQ use ") \ EM(fscache_cookie_new_acquire, "NEW acq ") \ EM(fscache_cookie_put_hash_collision, "PUT hcoll") \ + EM(fscache_cookie_put_lru, "PUT lru ") \ EM(fscache_cookie_put_over_queued, "PQ overq") \ EM(fscache_cookie_put_relinquish, "PUT relnq") \ EM(fscache_cookie_put_withdrawn, "PUT wthdn") \ EM(fscache_cookie_put_work, "PQ work ") \ EM(fscache_cookie_see_active, "- active") \ + EM(fscache_cookie_see_lru_do_one, "- lrudo") \ + EM(fscache_cookie_see_committing, "- x-cmt") \ EM(fscache_cookie_see_relinquish, "- x-rlq") \ EM(fscache_cookie_see_withdraw, "- x-wth") \ E_(fscache_cookie_see_work, "- work ") @@ -123,6 +134,7 @@ 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, "BEGIN lookup ") \ 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") \