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| author | David Howells <dhowells@redhat.com> | 2021-10-20 17:26:17 +0300 |
|---|---|---|
| committer | David Howells <dhowells@redhat.com> | 2022-01-07 12:22:19 +0300 |
| commit | e6acd3299badbfb5fb0231d42481d4f5dedf5599 (patch) | |
| tree | f7152cfc6fc1c6375b66b7dec4b49a58109a7b2a /include/linux/fscache-cache.h | |
| parent | 23e12e285a6ab7320a8bceead29cfe13190a6e3c (diff) | |
| download | linux-e6acd3299badbfb5fb0231d42481d4f5dedf5599.tar.xz | |
fscache: Implement volume-level access helpers
Add a pair of helper functions to manage access to a volume, pinning the
volume in place for the duration to prevent cache withdrawal from removing
it:
bool fscache_begin_volume_access(struct fscache_volume *volume,
enum fscache_access_trace why);
void fscache_end_volume_access(struct fscache_volume *volume,
enum fscache_access_trace why);
The way the access gate on the volume 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 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.
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/163819594158.215744.8285859817391683254.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906894315.143852.5454793807544710479.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967095028.1823006.9173132503876627466.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021501546.640689.9631510472149608443.stgit@warthog.procyon.org.uk/ # v4
Diffstat (limited to 'include/linux/fscache-cache.h')
| -rw-r--r-- | include/linux/fscache-cache.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h index c4355b888c91..fbbd8a2afe12 100644 --- a/include/linux/fscache-cache.h +++ b/include/linux/fscache-cache.h @@ -53,6 +53,10 @@ extern struct rw_semaphore fscache_addremove_sem; extern struct fscache_cache *fscache_acquire_cache(const char *name); extern void fscache_relinquish_cache(struct fscache_cache *cache); +extern void fscache_end_volume_access(struct fscache_volume *volume, + struct fscache_cookie *cookie, + enum fscache_access_trace why); + extern struct fscache_cookie *fscache_get_cookie(struct fscache_cookie *cookie, enum fscache_cookie_trace where); extern void fscache_put_cookie(struct fscache_cookie *cookie, |