linux-kernel - [PATCH v2 53/53] fscache, cachefiles: Display stat of culling events

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Date:   Fri, 22 Oct 2021 20:11:06 +0100
From:   David Howells <dhowells@...hat.com>
To:     linux-cachefs@...hat.com
Cc:     dhowells@...hat.com, Trond Myklebust <trondmy@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Steve French <sfrench@...ba.org>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Jeff Layton <jlayton@...nel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Omar Sandoval <osandov@...ndov.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
        linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 53/53] fscache, cachefiles: Display stat of culling events

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@...hat.com>
cc: linux-cachefs@...hat.com
---

 fs/cachefiles/namei.c         |    1 +
 fs/fscache/stats.c            |    7 +++++--
 include/linux/fscache-cache.h |    4 +++-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 9b0a14e37cfa..a118074826cd 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -661,6 +661,7 @@ int cachefiles_cull(struct cachefiles_cache *cache, struct dentry *dir,
 		goto error_unlock;
 
 	/*  actually remove the victim (drops the dir mutex) */
+	fscache_count_culled();
 	_debug("bury");
 
 	ret = cachefiles_bury_object(cache, NULL, dir, victim,
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index d34fb6e91d57..ee1b611e365d 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -48,6 +48,8 @@ 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
@@ -90,9 +92,10 @@ 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 7b3225c6c22f..e12f4163af61 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -181,15 +181,17 @@ 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
 
 extern struct workqueue_struct *fscache_wq;