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authorDavid Howells <dhowells@redhat.com>2021-10-20 15:26:17 +0100
committerDavid Howells <dhowells@redhat.com>2022-01-07 09:22:19 +0000
commite6acd3299badbfb5fb0231d42481d4f5dedf5599 (patch)
treef7152cfc6fc1c6375b66b7dec4b49a58109a7b2a /fs/fscache/internal.h
parent23e12e285a6ab7320a8bceead29cfe13190a6e3c (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.h3
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);