[PATCH 3.4 040/177] dm bufio: update last_accessed when relinking a buffer

[lizf]

From: Joe Thornber <ejt@xxxxxxxxxx>

3.4.106-rc1 review patch.  If anyone has any objections, please let me know.

------------------


commit eb76faf53b1ff7a77ce3f78cc98ad392ac70c2a0 upstream.

The 'last_accessed' member of the dm_buffer structure was only set when
the the buffer was created.  This led to each buffer being discarded
after dm_bufio_max_age time even if it was used recently.  In practice
this resulted in all thinp metadata being evicted soon after being read
-- this is particularly problematic for metadata intensive workloads
like multithreaded small random IO.

'last_accessed' is now updated each time the buffer is moved to the head
of the LRU list, so the buffer is now properly discarded if it was not
used in dm_bufio_max_age time.

Signed-off-by: Joe Thornber <ejt@xxxxxxxxxx>
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
---
 drivers/md/dm-bufio.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 6f99500..5abc8d6 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -467,6 +467,7 @@ static void __relink_lru(struct dm_buffer *b, int dirty)
 	b->list_mode = dirty;
 	list_del(&b->lru_list);
 	list_add(&b->lru_list, &c->lru[dirty]);
+	b->last_accessed = jiffies;
 }
 
 /*----------------------------------------------------------------
-- 
1.9.1

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