linux-kernel - [PATCH 3.12 76/82] xen-blkfront: don't add indirect pages to list when !feature

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Date:	Mon, 24 Aug 2015 11:09:36 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Bob Liu <bob.liu@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 76/82] xen-blkfront: don't add indirect pages to list when !feature_persistent

From: Bob Liu <bob.liu@...cle.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 7b0767502b5db11cb1f0daef2d01f6d71b1192dc upstream.

We should consider info->feature_persistent when adding indirect page to list
info->indirect_pages, else the BUG_ON() in blkif_free() would be triggered.

When we are using persistent grants the indirect_pages list
should always be empty because blkfront has pre-allocated enough
persistent pages to fill all requests on the ring.

Acked-by: Roger Pau Monné <roger.pau@...rix.com>
Signed-off-by: Bob Liu <bob.liu@...cle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/block/xen-blkfront.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 3bb5efdcdc8a..7d0eb3f8d629 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1090,8 +1090,10 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info,
 				 * Add the used indirect page back to the list of
 				 * available pages for indirect grefs.
 				 */
-				indirect_page = pfn_to_page(s->indirect_grants[i]->pfn);
-				list_add(&indirect_page->lru, &info->indirect_pages);
+				if (!info->feature_persistent) {
+					indirect_page = pfn_to_page(s->indirect_grants[i]->pfn);
+					list_add(&indirect_page->lru, &info->indirect_pages);
+				}
 				s->indirect_grants[i]->gref = GRANT_INVALID_REF;
 				list_add_tail(&s->indirect_grants[i]->node, &info->grants);
 			}
-- 
2.5.0

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