diff options
author | David Howells <dhowells@redhat.com> | 2021-10-20 17:53:34 +0300 |
---|---|---|
committer | David Howells <dhowells@redhat.com> | 2022-01-07 12:22:19 +0300 |
commit | 5d00e426f95e7ea036fec2a0aceb3f71d6dbdf92 (patch) | |
tree | b2808eb5f988c3c62f68310d1e58c265d0e91660 /include/linux/fscache-cache.h | |
parent | 29f18e79fe7c5f8011befeda9be6b220a350f947 (diff) | |
download | linux-5d00e426f95e7ea036fec2a0aceb3f71d6dbdf92.tar.xz |
fscache: Implement simple cookie state machine
Implement a very simple cookie state machine to handle lookup,
invalidation, withdrawal, relinquishment and, to be added later, commit on
LRU discard.
Three cache methods are provided: ->lookup_cookie() to look up and, if
necessary, create a data storage object; ->withdraw_cookie() to free the
resources associated with that object and potentially delete it; and
->prepare_to_write(), to do prepare for changes to the cached data to be
modified locally.
Changes
=======
ver #3:
- Fix a race between LRU discard and relinquishment whereby the former
would override the latter and thus the latter would never happen[1].
ver #2:
- Don't hold n_accesses elevated whilst cache is bound to a cookie, but
rather add a flag that prevents the state machine from being queued when
n_accesses reaches 0.
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/599331.1639410068@warthog.procyon.org.uk/ [1]
Link: https://lore.kernel.org/r/163819599657.215744.15799615296912341745.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906903925.143852.1805855338154353867.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967105456.1823006.14730395299835841776.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021510706.640689.7961423370243272583.stgit@warthog.procyon.org.uk/ # v4
Diffstat (limited to 'include/linux/fscache-cache.h')
-rw-r--r-- | include/linux/fscache-cache.h | 27 |
1 files changed, 25 insertions, 2 deletions
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 |