linux-kernel - [PATCH] drivers: xen-blkfront: blkif_recover: recheck feature-persistent

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Date:	Tue, 26 May 2015 08:11:34 +0800
From:	Bob Liu <bob.liu@...cle.com>
To:	xen-devel@...ts.xen.org
Cc:	david.vrabel@...rix.com, justing@...ctralogic.com,
	konrad.wilk@...cle.com, roger.pau@...rix.com,
	paul.durrant@...rix.com, julien.grall@...rix.com,
	boris.ostrovsky@...cle.com, linux-kernel@...r.kernel.org,
	Bob Liu <bob.liu@...cle.com>
Subject: [PATCH] drivers: xen-blkfront: blkif_recover: recheck feature-persistent

When migrate from !feature-persistent host to feature-persistent host, domU
still think new host/backend don't support persistent.
Dmesg like:
backed has not unmapped grant: 839
backed has not unmapped grant: 773
backed has not unmapped grant: 773
backed has not unmapped grant: 773
backed has not unmapped grant: 839

We should recheck whether the new backend support feature-persistent during
blkif_recover().

Signed-off-by: Bob Liu <bob.liu@...cle.com>
---
 drivers/block/xen-blkfront.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index d3c1a95..cad4d8c 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1504,7 +1504,7 @@ static int blkif_recover(struct blkfront_info *info)
 	int i;
 	struct request *req, *n;
 	struct blk_shadow *copy;
-	int rc;
+	int rc, persistent;
 	struct bio *bio, *cloned_bio;
 	struct bio_list bio_list, merge_bio;
 	unsigned int segs, offset;
@@ -1525,6 +1525,14 @@ static int blkif_recover(struct blkfront_info *info)
 	info->shadow_free = info->ring.req_prod_pvt;
 	info->shadow[BLK_RING_SIZE(info)-1].req.u.rw.id = 0x0fffffff;
 
+	/* Should check whether the new backend support feature-persistent */
+	rc = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+			    "feature-persistent", "%u", &persistent,
+			    NULL);
+	if (rc)
+		info->feature_persistent = 0;
+	else
+		info->feature_persistent = persistent;
 	rc = blkfront_setup_indirect(info);
 	if (rc) {
 		kfree(copy);
-- 
1.8.3.1

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