xen-blkback: fix memory leak when persistent grants are used

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@oracle.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Ian Campbell <Ian.Campbell@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xen.org
Cc: Anthony Liguori <aliguori@amazon.com>
Signed-off-by: Matt Rushton <mrushton@amazon.com>
Signed-off-by: Matt Wilson <msw@amazon.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 6620b73d04906191132d771dade31f9e00043e07..30ef7b390df5ca3e3712d3ee052196011456fbc7 100644 (file)
--- 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);