forked from Minki/linux
fscache: Provide and use cache methods to lookup/create/free a volume
Add cache methods to lookup, create and remove a volume. Looking up or creating the volume requires the cache pinning for access; freeing the volume requires the volume pinning for access. The ->acquire_volume() method is used to ask the cache backend to lookup and, if necessary, create a volume; the ->free_volume() method is used to free the resources for a volume. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/163819597821.215744.5225318658134989949.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906898645.143852.8537799955945956818.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967099771.1823006.1455197910571061835.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021507345.640689.4073511598838843040.stgit@warthog.procyon.org.uk/ # v4
This commit is contained in:
David Howells
parent
2e0c76aee2
commit
bfa22da3ed
@ -15,6 +15,8 @@ static struct hlist_bl_head fscache_volume_hash[1 << fscache_volume_hash_shift];
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static atomic_t fscache_volume_debug_id;
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static LIST_HEAD(fscache_volumes);
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static void fscache_create_volume_work(struct work_struct *work);
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struct fscache_volume *fscache_get_volume(struct fscache_volume *volume,
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enum fscache_volume_trace where)
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{
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@ -213,7 +215,7 @@ static struct fscache_volume *fscache_alloc_volume(const char *volume_key,
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volume->cache = cache;
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INIT_LIST_HEAD(&volume->proc_link);
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INIT_WORK(&volume->work, NULL /* PLACEHOLDER */);
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INIT_WORK(&volume->work, fscache_create_volume_work);
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refcount_set(&volume->ref, 1);
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spin_lock_init(&volume->lock);
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@ -249,6 +251,58 @@ err_cache:
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return NULL;
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}
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/*
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* Create a volume's representation on disk. Have a volume ref and a cache
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* access we have to release.
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*/
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static void fscache_create_volume_work(struct work_struct *work)
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{
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const struct fscache_cache_ops *ops;
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struct fscache_volume *volume =
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container_of(work, struct fscache_volume, work);
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fscache_see_volume(volume, fscache_volume_see_create_work);
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ops = volume->cache->ops;
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if (ops->acquire_volume)
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ops->acquire_volume(volume);
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fscache_end_cache_access(volume->cache,
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fscache_access_acquire_volume_end);
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clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags);
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wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING);
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fscache_put_volume(volume, fscache_volume_put_create_work);
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}
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/*
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* Dispatch a worker thread to create a volume's representation on disk.
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*/
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void fscache_create_volume(struct fscache_volume *volume, bool wait)
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{
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if (test_and_set_bit(FSCACHE_VOLUME_CREATING, &volume->flags))
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goto maybe_wait;
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if (volume->cache_priv)
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goto no_wait; /* We raced */
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if (!fscache_begin_cache_access(volume->cache,
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fscache_access_acquire_volume))
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goto no_wait;
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fscache_get_volume(volume, fscache_volume_get_create_work);
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if (!schedule_work(&volume->work))
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fscache_put_volume(volume, fscache_volume_put_create_work);
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maybe_wait:
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if (wait) {
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fscache_see_volume(volume, fscache_volume_wait_create_work);
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wait_on_bit(&volume->flags, FSCACHE_VOLUME_CREATING,
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TASK_UNINTERRUPTIBLE);
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}
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return;
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no_wait:
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clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags);
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wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING);
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}
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/*
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* Acquire a volume representation cookie and link it to a (proposed) cache.
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*/
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@ -269,7 +323,7 @@ struct fscache_volume *__fscache_acquire_volume(const char *volume_key,
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return ERR_PTR(-EBUSY);
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}
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// PLACEHOLDER: Create the volume if we have a cache available
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fscache_create_volume(volume, false);
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return volume;
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}
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EXPORT_SYMBOL(__fscache_acquire_volume);
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@ -316,7 +370,12 @@ static void fscache_free_volume(struct fscache_volume *volume)
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struct fscache_cache *cache = volume->cache;
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if (volume->cache_priv) {
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// PLACEHOLDER: Detach any attached cache
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__fscache_begin_volume_access(volume, NULL,
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fscache_access_relinquish_volume);
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if (volume->cache_priv)
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cache->ops->free_volume(volume);
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fscache_end_volume_access(volume, NULL,
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fscache_access_relinquish_volume_end);
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}
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down_write(&fscache_addremove_sem);
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@ -369,6 +428,30 @@ void __fscache_relinquish_volume(struct fscache_volume *volume,
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}
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EXPORT_SYMBOL(__fscache_relinquish_volume);
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/**
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* fscache_withdraw_volume - Withdraw a volume from being cached
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* @volume: Volume cookie
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*
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* Withdraw a cache volume from service, waiting for all accesses to complete
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* before returning.
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*/
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void fscache_withdraw_volume(struct fscache_volume *volume)
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{
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int n_accesses;
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_debug("withdraw V=%x", volume->debug_id);
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/* Allow wakeups on dec-to-0 */
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n_accesses = atomic_dec_return(&volume->n_accesses);
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trace_fscache_access_volume(volume->debug_id, 0,
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refcount_read(&volume->ref),
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n_accesses, fscache_access_cache_unpin);
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wait_var_event(&volume->n_accesses,
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atomic_read(&volume->n_accesses) == 0);
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}
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EXPORT_SYMBOL(fscache_withdraw_volume);
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#ifdef CONFIG_PROC_FS
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/*
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* Generate a list of volumes in /proc/fs/fscache/volumes
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@ -51,6 +51,12 @@ struct fscache_cache {
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struct fscache_cache_ops {
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/* name of cache provider */
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const char *name;
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/* Acquire a volume */
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void (*acquire_volume)(struct fscache_volume *volume);
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/* Free the cache's data attached to a volume */
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void (*free_volume)(struct fscache_volume *volume);
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};
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extern struct workqueue_struct *fscache_wq;
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@ -65,6 +71,7 @@ extern int fscache_add_cache(struct fscache_cache *cache,
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const struct fscache_cache_ops *ops,
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void *cache_priv);
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extern void fscache_withdraw_cache(struct fscache_cache *cache);
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extern void fscache_withdraw_volume(struct fscache_volume *volume);
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extern void fscache_end_volume_access(struct fscache_volume *volume,
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struct fscache_cookie *cookie,
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@ -64,8 +64,12 @@ enum fscache_cookie_trace {
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};
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enum fscache_access_trace {
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fscache_access_acquire_volume,
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fscache_access_acquire_volume_end,
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fscache_access_cache_pin,
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fscache_access_cache_unpin,
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fscache_access_relinquish_volume,
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fscache_access_relinquish_volume_end,
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fscache_access_unlive,
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};
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@ -96,7 +100,8 @@ enum fscache_access_trace {
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EM(fscache_volume_put_hash_collision, "PUT hcoll") \
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EM(fscache_volume_put_relinquish, "PUT relnq") \
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EM(fscache_volume_see_create_work, "SEE creat") \
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E_(fscache_volume_see_hash_wake, "SEE hwake")
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EM(fscache_volume_see_hash_wake, "SEE hwake") \
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E_(fscache_volume_wait_create_work, "WAIT crea")
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#define fscache_cookie_traces \
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EM(fscache_cookie_collision, "*COLLIDE*") \
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@ -115,8 +120,12 @@ enum fscache_access_trace {
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E_(fscache_cookie_see_work, "- work ")
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#define fscache_access_traces \
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EM(fscache_access_acquire_volume, "BEGIN acq_vol") \
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EM(fscache_access_acquire_volume_end, "END acq_vol") \
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EM(fscache_access_cache_pin, "PIN cache ") \
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EM(fscache_access_cache_unpin, "UNPIN cache ") \
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EM(fscache_access_relinquish_volume, "BEGIN rlq_vol") \
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EM(fscache_access_relinquish_volume_end,"END rlq_vol") \
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E_(fscache_access_unlive, "END unlive ")
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/*
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