linux-kernel - [PATCH 3.12 086/206] dm bufio: update last

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Message-Id: <15188b0745439aa1f686e6eb55cacabbe2ea0244.1416319692.git.jslaby@suse.cz>
Date:	Tue, 18 Nov 2014 15:07:21 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Joe Thornber <ejt@...hat.com>,
	Mikulas Patocka <mpatocka@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 086/206] dm bufio: update last_accessed when relinking a buffer

From: Joe Thornber <ejt@...hat.com>

3.12-stable 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@...hat.com>
Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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 5056c45be97f..bb8d23d55c4a 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -463,6 +463,7 @@ static void __relink_lru(struct dm_buffer *b, int dirty)
 	c->n_buffers[dirty]++;
 	b->list_mode = dirty;
 	list_move(&b->lru_list, &c->lru[dirty]);
+	b->last_accessed = jiffies;
 }
 
 /*----------------------------------------------------------------
-- 
2.1.3

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