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Commit 7901d141 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Jens Axboe
Browse files

xen/blkfront: Use QUEUE_ORDERED_DRAIN for old backends 



If there's no feature-barrier key in xenstore, then it means its a fairly
old backend which does uncached in-order writes, which means ORDERED_DRAIN
is appropriate.

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
parent 4dab46ff

drivers/block/xen-blkfront.c

+29 −16
Original line number Diff line number Diff line
@@ -420,26 +420,22 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size) 
static int xlvbd_barrier(struct blkfront_info *info)

{

	int err;

	unsigned ordered = QUEUE_ORDERED_NONE;

	const char *barrier;



	/*

	 * If we don't have barrier support, then there's really no

	 * way to guarantee write ordering, so we really just have to

	 * send writes to the backend and hope for the best.  If

	 * barriers are supported then we can treat them as proper

	 * ordering tags.

	 */

	if (info->feature_barrier)

		ordered = QUEUE_ORDERED_TAG;

	switch (info->feature_barrier) {

	case QUEUE_ORDERED_DRAIN:	barrier = "enabled (drain)"; break;

	case QUEUE_ORDERED_TAG:		barrier = "enabled (tag)"; break;

	case QUEUE_ORDERED_NONE:	barrier = "disabled"; break;

	default:			return -EINVAL;

	}



	err = blk_queue_ordered(info->rq, ordered);

	err = blk_queue_ordered(info->rq, info->feature_barrier);



	if (err)

		return err;



	printk(KERN_INFO "blkfront: %s: barriers %s\n",

	       info->gd->disk_name,

	       info->feature_barrier ? "enabled" : "disabled");

	       info->gd->disk_name, barrier);

	return 0;

}
@@ -665,7 +661,7 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) 
				printk(KERN_WARNING "blkfront: %s: write barrier op failed\n",

				       info->gd->disk_name);

				error = -EOPNOTSUPP;

				info->feature_barrier = 0;

				info->feature_barrier = QUEUE_ORDERED_NONE;

				xlvbd_barrier(info);

			}

			/* fall through */
@@ -1003,6 +999,7 @@ static void blkfront_connect(struct blkfront_info *info) 
	unsigned long sector_size;

	unsigned int binfo;

	int err;

	int barrier;



	switch (info->connected) {

	case BLKIF_STATE_CONNECTED:
@@ -1043,10 +1040,26 @@ static void blkfront_connect(struct blkfront_info *info) 
	}



	err = xenbus_gather(XBT_NIL, info->xbdev->otherend,

			    "feature-barrier", "%lu", &info->feature_barrier,

			    "feature-barrier", "%lu", &barrier,

			    NULL);



	/*

	 * If there's no "feature-barrier" defined, then it means

	 * we're dealing with a very old backend which writes

	 * synchronously; draining will do what needs to get done.

	 *

	 * If there are barriers, then we can do full queued writes

	 * with tagged barriers.

	 *

	 * If barriers are not supported, then there's no much we can

	 * do, so just set ordering to NONE.

	 */

	if (err)

		info->feature_barrier = 0;

		info->feature_barrier = QUEUE_ORDERED_DRAIN;

	else if (barrier)

		info->feature_barrier = QUEUE_ORDERED_TAG;

	else

		info->feature_barrier = QUEUE_ORDERED_NONE;



	err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size);

	if (err) {