linux-kernel - [PATCH] Input: xen-kbdfront - free grant table entry in xenkbd_disconnect

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Message-Id: <1413423992-3005-1-git-send-email-hansechang@gmail.com>
Date:	Thu, 16 Oct 2014 09:46:32 +0800
From:	hansechang@...il.com
To:	linux-kernel@...r.kernel.org, xen-devel@...ts.xen.org
Cc:	konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
	david.vrabel@...rix.com, Ian.Campbell@...citrix.com,
	dgdegra@...ho.nsa.gov, jinsong.liu@...baba-inc.com,
	Chang Huaixin <huaixin.chx@...baba-inc.com>
Subject: [PATCH] Input: xen-kbdfront - free grant table entry in xenkbd_disconnect_backend

From: Chang Huaixin <huaixin.chx@...baba-inc.com>

xenkbd_disconnect_backend doesn't free grant table entry.
This bug affects live migration.

xenkbd_disconnect_backend uses gnttab_end_foreign_access_ref
to handle grant table entry which doesn't really free an entry.

Thus every time we do xenkbd_resume, grant table entry increses
by one. As an grant table entry occupies 8 bytes, an grant table
page has at most 512 entries. Every 512 times we do xenkdb_resume,
grant table pages increses by one.

After around 3500 times of live migration, grant table pages
will increase by 7, causing too many pages to populate and hitting
max_pages limit when assigning pages.Thus assign_pages will fail,
so will live migration.

Signed-off-by: Chang Huaixin <huaixin.chx@...baba-inc.com>
---
 drivers/input/misc/xen-kbdfront.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
index fbfdc10..e2ecfc6 100644
--- a/drivers/input/misc/xen-kbdfront.c
+++ b/drivers/input/misc/xen-kbdfront.c
@@ -285,7 +285,7 @@ static int xenkbd_connect_backend(struct xenbus_device *dev,
  error_evtchan:
 	xenbus_free_evtchn(dev, evtchn);
  error_grant:
-	gnttab_end_foreign_access_ref(info->gref, 0);
+	gnttab_end_foreign_access(info->gref, 0, 0UL);
 	info->gref = -1;
 	return ret;
 }
@@ -296,7 +296,7 @@ static void xenkbd_disconnect_backend(struct xenkbd_info *info)
 		unbind_from_irqhandler(info->irq, info);
 	info->irq = -1;
 	if (info->gref >= 0)
-		gnttab_end_foreign_access_ref(info->gref, 0);
+		gnttab_end_foreign_access(info->gref, 0, 0UL);
 	info->gref = -1;
 }
 
-- 
1.9.1

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