diff options
author | David Howells <dhowells@redhat.com> | 2021-10-20 15:26:17 +0100 |
---|---|---|
committer | David Howells <dhowells@redhat.com> | 2022-01-07 09:22:19 +0000 |
commit | e6acd3299badbfb5fb0231d42481d4f5dedf5599 (patch) | |
tree | f7152cfc6fc1c6375b66b7dec4b49a58109a7b2a /fs/fscache/internal.h | |
parent | 23e12e285a6ab7320a8bceead29cfe13190a6e3c (diff) |
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 'fs/fscache/internal.h')
-rw-r--r-- | fs/fscache/internal.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h index be29816b37ef..91a4ea08ec0b 100644 --- a/fs/fscache/internal.h +++ b/fs/fscache/internal.h @@ -130,6 +130,9 @@ struct fscache_volume *fscache_get_volume(struct fscache_volume *volume, enum fscache_volume_trace where); void fscache_put_volume(struct fscache_volume *volume, enum fscache_volume_trace where); +bool fscache_begin_volume_access(struct fscache_volume *volume, + struct fscache_cookie *cookie, + enum fscache_access_trace why); void fscache_create_volume(struct fscache_volume *volume, bool wait); |