FS-Cache: Count culled objects and objects rejected due to lack of space

Count the number of objects that get culled by the cache backend and the
number of objects that the cache backend declines to instantiate due to lack
of space in the cache.

These numbers are made available through /proc/fs/fscache/stats

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Steve Dickson <steved@redhat.com>
Acked-by: Jeff Layton <jeff.layton@primarydata.com>

2 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/filesystems/caching/backend-api.txt b/Documentation/filesystems/caching/backend-api.txt
index 277d1e810670..c0bd5677271b 100644
--- a/Documentation/filesystems/caching/backend-api.txt
+++ b/Documentation/filesystems/caching/backend-api.txt
@@ -676,6 +676,29 @@ FS-Cache provides some utilities that a cache backend may make use of:
      as possible.
 
 
+ (*) Indicate that a stale object was found and discarded:
+
+        void fscache_object_retrying_stale(struct fscache_object *object);
+
+     This is called to indicate that the lookup procedure found an object in
+     the cache that the netfs decided was stale.  The object has been
+     discarded from the cache and the lookup will be performed again.
+
+
+ (*) Indicate that the caching backend killed an object:
+
+        void fscache_object_mark_killed(struct fscache_object *object,
+                                        enum fscache_why_object_killed why);
+
+     This is called to indicate that the cache backend preemptively killed an
+     object.  The why parameter should be set to indicate the reason:
+
+        FSCACHE_OBJECT_IS_STALE - the object was stale and needs discarding.
+        FSCACHE_OBJECT_NO_SPACE - there was insufficient cache space
+        FSCACHE_OBJECT_WAS_RETIRED - the object was retired when relinquished.
+        FSCACHE_OBJECT_WAS_CULLED - the object was culled to make space.
+
+
  (*) Get and release references on a retrieval record:
 
         void fscache_get_retrieval(struct fscache_retrieval *op);
diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt
index 770267af5b3e..66fa7fbccfa4 100644
--- a/Documentation/filesystems/caching/fscache.txt
+++ b/Documentation/filesystems/caching/fscache.txt
@@ -303,6 +303,10 @@ proc files.
                 wrp=N   Number of in-progress write_page() cache ops
                 ucp=N   Number of in-progress uncache_page() cache ops
                 dsp=N   Number of in-progress dissociate_pages() cache ops
+        CacheEv nsp=N   Number of object lookups/creations rejected due to lack of space
+                stl=N   Number of stale objects deleted
+                rtr=N   Number of objects retired when relinquished
+                cul=N   Number of objects culled
 
 
  (*) /proc/fs/fscache/histogram