[3.16.y-ckt stable] Patch "xen-blkfront: don't add indirect pages to list when !feature_persistent" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    xen-blkfront: don't add indirect pages to list when !feature_persistent

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt17.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From af4209563da5df8cb676e6d483768deb8df16cdd Mon Sep 17 00:00:00 2001
From: Bob Liu <bob.liu at oracle.com>
Date: Wed, 22 Jul 2015 14:40:09 +0800
Subject: xen-blkfront: don't add indirect pages to list when
 !feature_persistent
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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 at citrix.com>
Signed-off-by: Bob Liu <bob.liu at oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 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 5deb235bd18f..2a29cf69cd73 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1093,8 +1093,10 @@ 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);
 			}