[PATCH v4 55/68] fscache, cachefiles: Display stat of culling events

[David Howells]

Add a stat counter of culling events whereby the cache backend culls a file
to make space (when asked by cachefilesd in this case) and display in
/proc/fs/fscache/stats.

Signed-off-by: David Howells <dhowells at redhat.com>
cc: linux-cachefs at redhat.com
Link: https://lore.kernel.org/r/163819654165.215744.3797804661644212436.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906961387.143852.9291157239960289090.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967168266.1823006.14436200166581605746.stgit@warthog.procyon.org.uk/ # v3
---

 fs/cachefiles/namei.c         |    1 +
 fs/fscache/stats.c            |    7 +++++--
 include/linux/fscache-cache.h |    3 +++
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index ab3ca598acac..9bd692870617 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -805,6 +805,7 @@ int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
 	if (ret < 0)
 		goto error;
 
+	fscache_count_culled();
 	dput(victim);
 	_leave(" = 0");
 	return 0;
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index db2f4e225dd9..fc94e5e79f1c 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -46,6 +46,8 @@ atomic_t fscache_n_no_write_space;
 EXPORT_SYMBOL(fscache_n_no_write_space);
 atomic_t fscache_n_no_create_space;
 EXPORT_SYMBOL(fscache_n_no_create_space);
+atomic_t fscache_n_culled;
+EXPORT_SYMBOL(fscache_n_culled);
 
 /*
  * display the general statistics
@@ -86,9 +88,10 @@ int fscache_stats_show(struct seq_file *m, void *v)
 		   atomic_read(&fscache_n_relinquishes_retire),
 		   atomic_read(&fscache_n_relinquishes_dropped));
 
-	seq_printf(m, "NoSpace: nwr=%u ncr=%u\n",
+	seq_printf(m, "NoSpace: nwr=%u ncr=%u cull=%u\n",
 		   atomic_read(&fscache_n_no_write_space),
-		   atomic_read(&fscache_n_no_create_space));
+		   atomic_read(&fscache_n_no_create_space),
+		   atomic_read(&fscache_n_culled));
 
 	seq_printf(m, "IO     : rd=%u wr=%u\n",
 		   atomic_read(&fscache_n_read),
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index 007e47f38610..a174cedf4d90 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -188,15 +188,18 @@ extern atomic_t fscache_n_read;
 extern atomic_t fscache_n_write;
 extern atomic_t fscache_n_no_write_space;
 extern atomic_t fscache_n_no_create_space;
+extern atomic_t fscache_n_culled;
 #define fscache_count_read() atomic_inc(&fscache_n_read)
 #define fscache_count_write() atomic_inc(&fscache_n_write)
 #define fscache_count_no_write_space() atomic_inc(&fscache_n_no_write_space)
 #define fscache_count_no_create_space() atomic_inc(&fscache_n_no_create_space)
+#define fscache_count_culled() atomic_inc(&fscache_n_culled)
 #else
 #define fscache_count_read() do {} while(0)
 #define fscache_count_write() do {} while(0)
 #define fscache_count_no_write_space() do {} while(0)
 #define fscache_count_no_create_space() do {} while(0)
+#define fscache_count_culled() do {} while(0)
 #endif
 
 #endif /* _LINUX_FSCACHE_CACHE_H */