linux-kernel - [PATCH] xen-blkback: fix memory leak when persistent grants are used

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Date:	Thu, 23 Jan 2014 11:28:46 -0800
From:	Matt Wilson <msw@...ux.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	Matt Rushton <mrushton@...zon.com>,
	Roger Pau Monné <roger.pau@...rix.com>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	David Vrabel <david.vrabel@...rix.com>,
	linux-kernel@...r.kernel.org, xen-devel@...ts.xen.org,
	Anthony Liguori <aliguori@...zon.com>,
	Matt Wilson <msw@...zon.com>
Subject: [PATCH] xen-blkback: fix memory leak when persistent grants are used

From: Matt Rushton <mrushton@...zon.com>

Currently shrink_free_pagepool() is called before the pages used for
persistent grants are released via free_persistent_gnts(). This
results in a memory leak when a VBD that uses persistent grants is
torn down.

Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: "Roger Pau Monné" <roger.pau@...rix.com>
Cc: Ian Campbell <Ian.Campbell@...rix.com>
Cc: David Vrabel <david.vrabel@...rix.com>
Cc: linux-kernel@...r.kernel.org
Cc: xen-devel@...ts.xen.org
Cc: Anthony Liguori <aliguori@...zon.com>
Signed-off-by: Matt Rushton <mrushton@...zon.com>
Signed-off-by: Matt Wilson <msw@...zon.com>
---
 drivers/block/xen-blkback/blkback.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 6620b73..30ef7b3 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -625,9 +625,6 @@ purge_gnt_list:
 			print_stats(blkif);
 	}
 
-	/* Since we are shutting down remove all pages from the buffer */
-	shrink_free_pagepool(blkif, 0 /* All */);
-
 	/* Free all persistent grant pages */
 	if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
 		free_persistent_gnts(blkif, &blkif->persistent_gnts,
@@ -636,6 +633,9 @@ purge_gnt_list:
 	BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
 	blkif->persistent_gnt_c = 0;
 
+	/* Since we are shutting down remove all pages from the buffer */
+	shrink_free_pagepool(blkif, 0 /* All */);
+
 	if (log_stats)
 		print_stats(blkif);
 
-- 
1.7.9.5

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