diff options
Diffstat (limited to 'fs/fscache/volume.c')
| -rw-r--r-- | fs/fscache/volume.c | 520 |
1 files changed, 0 insertions, 520 deletions
diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c deleted file mode 100644 index cdf991bdd..000000000 --- a/fs/fscache/volume.c +++ /dev/null @@ -1,520 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0-or-later -/* Volume-level cache cookie handling. - * - * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. - * Written by David Howells (dhowells@redhat.com) - */ - -#define FSCACHE_DEBUG_LEVEL COOKIE -#include <linux/export.h> -#include <linux/slab.h> -#include "internal.h" - -#define fscache_volume_hash_shift 10 -static struct hlist_bl_head fscache_volume_hash[1 << fscache_volume_hash_shift]; -static atomic_t fscache_volume_debug_id; -static LIST_HEAD(fscache_volumes); - -static void fscache_create_volume_work(struct work_struct *work); - -struct fscache_volume *fscache_get_volume(struct fscache_volume *volume, - enum fscache_volume_trace where) -{ - int ref; - - __refcount_inc(&volume->ref, &ref); - trace_fscache_volume(volume->debug_id, ref + 1, where); - return volume; -} - -static void fscache_see_volume(struct fscache_volume *volume, - enum fscache_volume_trace where) -{ - int ref = refcount_read(&volume->ref); - - trace_fscache_volume(volume->debug_id, ref, where); -} - -/* - * Pin the cache behind a volume so that we can access it. - */ -static void __fscache_begin_volume_access(struct fscache_volume *volume, - struct fscache_cookie *cookie, - enum fscache_access_trace why) -{ - int n_accesses; - - n_accesses = atomic_inc_return(&volume->n_accesses); - smp_mb__after_atomic(); - trace_fscache_access_volume(volume->debug_id, cookie ? cookie->debug_id : 0, - refcount_read(&volume->ref), - n_accesses, why); -} - -/** - * fscache_begin_volume_access - Pin a cache so a volume can be accessed - * @volume: The volume cookie - * @cookie: A datafile cookie for a tracing reference (or NULL) - * @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 a volume 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 volume's n_accesses - * count and then recheck the cache liveness, ending the access if it - * ceased to be live. - * - * (3) When we end the access, we decrement the volume's n_accesses and wake - * up the any waiters if it reaches 0. - * - * (4) Whilst the cache is caching, the volume's 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, the volume's n_accesses is decremented and we wait for it to - * become 0. - * - * The datafile @cookie and the @why indicator are merely provided for tracing - * purposes. - */ -bool fscache_begin_volume_access(struct fscache_volume *volume, - struct fscache_cookie *cookie, - enum fscache_access_trace why) -{ - if (!fscache_cache_is_live(volume->cache)) - return false; - __fscache_begin_volume_access(volume, cookie, why); - if (!fscache_cache_is_live(volume->cache)) { - fscache_end_volume_access(volume, cookie, fscache_access_unlive); - return false; - } - return true; -} - -/** - * fscache_end_volume_access - Unpin a cache at the end of an access. - * @volume: The volume cookie - * @cookie: A datafile cookie for a tracing reference (or NULL) - * @why: An indication of the circumstances of the access for tracing - * - * Unpin a cache volume after we've accessed it. The datafile @cookie and the - * @why indicator are merely provided for tracing purposes. - */ -void fscache_end_volume_access(struct fscache_volume *volume, - struct fscache_cookie *cookie, - enum fscache_access_trace why) -{ - int n_accesses; - - smp_mb__before_atomic(); - n_accesses = atomic_dec_return(&volume->n_accesses); - trace_fscache_access_volume(volume->debug_id, cookie ? cookie->debug_id : 0, - refcount_read(&volume->ref), - n_accesses, why); - if (n_accesses == 0) - wake_up_var(&volume->n_accesses); -} -EXPORT_SYMBOL(fscache_end_volume_access); - -static bool fscache_volume_same(const struct fscache_volume *a, - const struct fscache_volume *b) -{ - size_t klen; - - if (a->key_hash != b->key_hash || - a->cache != b->cache || - a->key[0] != b->key[0]) - return false; - - klen = round_up(a->key[0] + 1, sizeof(__le32)); - return memcmp(a->key, b->key, klen) == 0; -} - -static bool fscache_is_acquire_pending(struct fscache_volume *volume) -{ - return test_bit(FSCACHE_VOLUME_ACQUIRE_PENDING, &volume->flags); -} - -static void fscache_wait_on_volume_collision(struct fscache_volume *candidate, - unsigned int collidee_debug_id) -{ - wait_on_bit_timeout(&candidate->flags, FSCACHE_VOLUME_ACQUIRE_PENDING, - TASK_UNINTERRUPTIBLE, 20 * HZ); - if (fscache_is_acquire_pending(candidate)) { - pr_notice("Potential volume collision new=%08x old=%08x", - candidate->debug_id, collidee_debug_id); - fscache_stat(&fscache_n_volumes_collision); - wait_on_bit(&candidate->flags, FSCACHE_VOLUME_ACQUIRE_PENDING, - TASK_UNINTERRUPTIBLE); - } -} - -/* - * Attempt to insert the new volume into the hash. If there's a collision, we - * wait for the old volume to complete if it's being relinquished and an error - * otherwise. - */ -static bool fscache_hash_volume(struct fscache_volume *candidate) -{ - struct fscache_volume *cursor; - struct hlist_bl_head *h; - struct hlist_bl_node *p; - unsigned int bucket, collidee_debug_id = 0; - - bucket = candidate->key_hash & (ARRAY_SIZE(fscache_volume_hash) - 1); - h = &fscache_volume_hash[bucket]; - - hlist_bl_lock(h); - hlist_bl_for_each_entry(cursor, p, h, hash_link) { - if (fscache_volume_same(candidate, cursor)) { - if (!test_bit(FSCACHE_VOLUME_RELINQUISHED, &cursor->flags)) - goto collision; - fscache_see_volume(cursor, fscache_volume_get_hash_collision); - set_bit(FSCACHE_VOLUME_COLLIDED_WITH, &cursor->flags); - set_bit(FSCACHE_VOLUME_ACQUIRE_PENDING, &candidate->flags); - collidee_debug_id = cursor->debug_id; - break; - } - } - - hlist_bl_add_head(&candidate->hash_link, h); - hlist_bl_unlock(h); - - if (fscache_is_acquire_pending(candidate)) - fscache_wait_on_volume_collision(candidate, collidee_debug_id); - return true; - -collision: - fscache_see_volume(cursor, fscache_volume_collision); - hlist_bl_unlock(h); - return false; -} - -/* - * Allocate and initialise a volume representation cookie. - */ -static struct fscache_volume *fscache_alloc_volume(const char *volume_key, - const char *cache_name, - const void *coherency_data, - size_t coherency_len) -{ - struct fscache_volume *volume; - struct fscache_cache *cache; - size_t klen, hlen; - u8 *key; - - klen = strlen(volume_key); - if (klen > NAME_MAX) - return NULL; - - if (!coherency_data) - coherency_len = 0; - - cache = fscache_lookup_cache(cache_name, false); - if (IS_ERR(cache)) - return NULL; - - volume = kzalloc(struct_size(volume, coherency, coherency_len), - GFP_KERNEL); - if (!volume) - goto err_cache; - - volume->cache = cache; - volume->coherency_len = coherency_len; - if (coherency_data) - memcpy(volume->coherency, coherency_data, coherency_len); - INIT_LIST_HEAD(&volume->proc_link); - INIT_WORK(&volume->work, fscache_create_volume_work); - refcount_set(&volume->ref, 1); - spin_lock_init(&volume->lock); - - /* Stick the length on the front of the key and pad it out to make - * hashing easier. - */ - hlen = round_up(1 + klen + 1, sizeof(__le32)); - key = kzalloc(hlen, GFP_KERNEL); - if (!key) - goto err_vol; - key[0] = klen; - memcpy(key + 1, volume_key, klen); - - volume->key = key; - volume->key_hash = fscache_hash(0, key, hlen); - - volume->debug_id = atomic_inc_return(&fscache_volume_debug_id); - down_write(&fscache_addremove_sem); - atomic_inc(&cache->n_volumes); - list_add_tail(&volume->proc_link, &fscache_volumes); - fscache_see_volume(volume, fscache_volume_new_acquire); - fscache_stat(&fscache_n_volumes); - up_write(&fscache_addremove_sem); - _leave(" = v=%x", volume->debug_id); - return volume; - -err_vol: - kfree(volume); -err_cache: - fscache_put_cache(cache, fscache_cache_put_alloc_volume); - fscache_stat(&fscache_n_volumes_nomem); - return NULL; -} - -/* - * Create a volume's representation on disk. Have a volume ref and a cache - * access we have to release. - */ -static void fscache_create_volume_work(struct work_struct *work) -{ - const struct fscache_cache_ops *ops; - struct fscache_volume *volume = - container_of(work, struct fscache_volume, work); - - fscache_see_volume(volume, fscache_volume_see_create_work); - - ops = volume->cache->ops; - if (ops->acquire_volume) - ops->acquire_volume(volume); - fscache_end_cache_access(volume->cache, - fscache_access_acquire_volume_end); - - clear_and_wake_up_bit(FSCACHE_VOLUME_CREATING, &volume->flags); - fscache_put_volume(volume, fscache_volume_put_create_work); -} - -/* - * Dispatch a worker thread to create a volume's representation on disk. - */ -void fscache_create_volume(struct fscache_volume *volume, bool wait) -{ - if (test_and_set_bit(FSCACHE_VOLUME_CREATING, &volume->flags)) - goto maybe_wait; - if (volume->cache_priv) - goto no_wait; /* We raced */ - if (!fscache_begin_cache_access(volume->cache, - fscache_access_acquire_volume)) - goto no_wait; - - fscache_get_volume(volume, fscache_volume_get_create_work); - if (!schedule_work(&volume->work)) - fscache_put_volume(volume, fscache_volume_put_create_work); - -maybe_wait: - if (wait) { - fscache_see_volume(volume, fscache_volume_wait_create_work); - wait_on_bit(&volume->flags, FSCACHE_VOLUME_CREATING, - TASK_UNINTERRUPTIBLE); - } - return; -no_wait: - clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags); - wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING); -} - -/* - * Acquire a volume representation cookie and link it to a (proposed) cache. - */ -struct fscache_volume *__fscache_acquire_volume(const char *volume_key, - const char *cache_name, - const void *coherency_data, - size_t coherency_len) -{ - struct fscache_volume *volume; - - volume = fscache_alloc_volume(volume_key, cache_name, - coherency_data, coherency_len); - if (!volume) - return ERR_PTR(-ENOMEM); - - if (!fscache_hash_volume(volume)) { - fscache_put_volume(volume, fscache_volume_put_hash_collision); - return ERR_PTR(-EBUSY); - } - - fscache_create_volume(volume, false); - return volume; -} -EXPORT_SYMBOL(__fscache_acquire_volume); - -static void fscache_wake_pending_volume(struct fscache_volume *volume, - struct hlist_bl_head *h) -{ - struct fscache_volume *cursor; - struct hlist_bl_node *p; - - hlist_bl_for_each_entry(cursor, p, h, hash_link) { - if (fscache_volume_same(cursor, volume)) { - fscache_see_volume(cursor, fscache_volume_see_hash_wake); - clear_and_wake_up_bit(FSCACHE_VOLUME_ACQUIRE_PENDING, - &cursor->flags); - return; - } - } -} - -/* - * Remove a volume cookie from the hash table. - */ -static void fscache_unhash_volume(struct fscache_volume *volume) -{ - struct hlist_bl_head *h; - unsigned int bucket; - - bucket = volume->key_hash & (ARRAY_SIZE(fscache_volume_hash) - 1); - h = &fscache_volume_hash[bucket]; - - hlist_bl_lock(h); - hlist_bl_del(&volume->hash_link); - if (test_bit(FSCACHE_VOLUME_COLLIDED_WITH, &volume->flags)) - fscache_wake_pending_volume(volume, h); - hlist_bl_unlock(h); -} - -/* - * Drop a cache's volume attachments. - */ -static void fscache_free_volume(struct fscache_volume *volume) -{ - struct fscache_cache *cache = volume->cache; - - if (volume->cache_priv) { - __fscache_begin_volume_access(volume, NULL, - fscache_access_relinquish_volume); - if (volume->cache_priv) - cache->ops->free_volume(volume); - fscache_end_volume_access(volume, NULL, - fscache_access_relinquish_volume_end); - } - - down_write(&fscache_addremove_sem); - list_del_init(&volume->proc_link); - atomic_dec(&volume->cache->n_volumes); - up_write(&fscache_addremove_sem); - - if (!hlist_bl_unhashed(&volume->hash_link)) - fscache_unhash_volume(volume); - - trace_fscache_volume(volume->debug_id, 0, fscache_volume_free); - kfree(volume->key); - kfree(volume); - fscache_stat_d(&fscache_n_volumes); - fscache_put_cache(cache, fscache_cache_put_volume); -} - -/* - * Drop a reference to a volume cookie. - */ -void fscache_put_volume(struct fscache_volume *volume, - enum fscache_volume_trace where) -{ - if (volume) { - unsigned int debug_id = volume->debug_id; - bool zero; - int ref; - - zero = __refcount_dec_and_test(&volume->ref, &ref); - trace_fscache_volume(debug_id, ref - 1, where); - if (zero) - fscache_free_volume(volume); - } -} - -/* - * Relinquish a volume representation cookie. - */ -void __fscache_relinquish_volume(struct fscache_volume *volume, - const void *coherency_data, - bool invalidate) -{ - if (WARN_ON(test_and_set_bit(FSCACHE_VOLUME_RELINQUISHED, &volume->flags))) - return; - - if (invalidate) { - set_bit(FSCACHE_VOLUME_INVALIDATE, &volume->flags); - } else if (coherency_data) { - memcpy(volume->coherency, coherency_data, volume->coherency_len); - } - - fscache_put_volume(volume, fscache_volume_put_relinquish); -} -EXPORT_SYMBOL(__fscache_relinquish_volume); - -/** - * fscache_withdraw_volume - Withdraw a volume from being cached - * @volume: Volume cookie - * - * Withdraw a cache volume from service, waiting for all accesses to complete - * before returning. - */ -void fscache_withdraw_volume(struct fscache_volume *volume) -{ - int n_accesses; - - _debug("withdraw V=%x", volume->debug_id); - - /* Allow wakeups on dec-to-0 */ - n_accesses = atomic_dec_return(&volume->n_accesses); - trace_fscache_access_volume(volume->debug_id, 0, - refcount_read(&volume->ref), - n_accesses, fscache_access_cache_unpin); - - wait_var_event(&volume->n_accesses, - atomic_read(&volume->n_accesses) == 0); -} -EXPORT_SYMBOL(fscache_withdraw_volume); - -#ifdef CONFIG_PROC_FS -/* - * Generate a list of volumes in /proc/fs/fscache/volumes - */ -static int fscache_volumes_seq_show(struct seq_file *m, void *v) -{ - struct fscache_volume *volume; - - if (v == &fscache_volumes) { - seq_puts(m, - "VOLUME REF nCOOK ACC FL CACHE KEY\n" - "======== ===== ===== === == =============== ================\n"); - return 0; - } - - volume = list_entry(v, struct fscache_volume, proc_link); - seq_printf(m, - "%08x %5d %5d %3d %02lx %-15.15s %s\n", - volume->debug_id, - refcount_read(&volume->ref), - atomic_read(&volume->n_cookies), - atomic_read(&volume->n_accesses), - volume->flags, - volume->cache->name ?: "-", - volume->key + 1); - return 0; -} - -static void *fscache_volumes_seq_start(struct seq_file *m, loff_t *_pos) - __acquires(&fscache_addremove_sem) -{ - down_read(&fscache_addremove_sem); - return seq_list_start_head(&fscache_volumes, *_pos); -} - -static void *fscache_volumes_seq_next(struct seq_file *m, void *v, loff_t *_pos) -{ - return seq_list_next(v, &fscache_volumes, _pos); -} - -static void fscache_volumes_seq_stop(struct seq_file *m, void *v) - __releases(&fscache_addremove_sem) -{ - up_read(&fscache_addremove_sem); -} - -const struct seq_operations fscache_volumes_seq_ops = { - .start = fscache_volumes_seq_start, - .next = fscache_volumes_seq_next, - .stop = fscache_volumes_seq_stop, - .show = fscache_volumes_seq_show, -}; -#endif /* CONFIG_PROC_FS */ |