Re: [PATCH] xen-blkfront: don't make discard-alignment mandatory

Don't require the discard-alignment xenstore node to be present in
order to correctly setup the feature. This can happen with versions of
QEMU that only write the discard-granularity but not the
discard-alignment node.

Assume discard-alignment is 0 if not present. While there also fix the
logic to not enable the discard feature if discard-granularity is not
present.

Reported-by: Arthur Borsboom <redacted>
Signed-off-by: Roger Pau Monné <redacted>
---
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Konrad Rzeszutek Wilk <redacted>
Cc: "Roger Pau Monné" <redacted>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: xen-devel@lists.xenproject.org
Cc: linux-block@vger.kernel.org
Cc: Arthur Borsboom <redacted>
---
  drivers/block/xen-blkfront.c | 25 +++++++++++++------------
  1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 5265975b3fba..5a93f7cc2939 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c

@@ -2179,22 +2179,23 @@ static void blkfront_closing(struct blkfront_info *info)
  
  static void blkfront_setup_discard(struct blkfront_info *info)
  {
-	int err;
-	unsigned int discard_granularity;
-	unsigned int discard_alignment;
+	unsigned int discard_granularity = 0;
+	unsigned int discard_alignment = 0;
+	unsigned int discard_secure = 0;
  
-	info->feature_discard = 1;
-	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
+	xenbus_gather(XBT_NIL, info->xbdev->otherend,
  		"discard-granularity", "%u", &discard_granularity,
  		"discard-alignment", "%u", &discard_alignment,
+		"discard-secure", "%u", &discard_secure,
  		NULL);