[Xen-devel] [PATCH] xen-blkback: fix memory leak when persistent grants are used

[Matt Wilson <msw@xxxxxxxxx>]

From: Matt Rushton <mrushton@xxxxxxxxxx>

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@xxxxxxxxxx>
Cc: "Roger Pau MonnÃ" <roger.pau@xxxxxxxxxx>
Cc: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxx
Cc: Anthony Liguori <aliguori@xxxxxxxxxx>
Signed-off-by: Matt Rushton <mrushton@xxxxxxxxxx>
Signed-off-by: Matt Wilson <msw@xxxxxxxxxx>
---
 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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