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Commit d50babbe authored by Bob Liu's avatar Bob Liu Committed by Konrad Rzeszutek Wilk
Browse files

xen-blkfront: introduce blkfront_gather_backend_features() 

There is a bug when migrate from !feature-persistent host to feature-persistent
host, because domU still thinks new host/backend doesn'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

The fix is to recheck feature-persistent of new backend in blkif_recover().
See: https://lkml.org/lkml/2015/5/25/469



As Roger suggested, we can split the part of blkfront_connect that checks for
optional features, like persistent grants, indirect descriptors and
flush/barrier features to a separate function and call it from both
blkfront_connect and blkif_recover

Acked-by: default avatarRoger Pau Monné <roger.pau@citrix.com>
Signed-off-by: default avatarBob Liu <bob.liu@oracle.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent a9b54bb9

drivers/block/xen-blkfront.c

+68 −54
Original line number Diff line number Diff line
@@ -179,6 +179,7 @@ static DEFINE_SPINLOCK(minor_lock); 
	((_segs + SEGS_PER_INDIRECT_FRAME - 1)/SEGS_PER_INDIRECT_FRAME)



static int blkfront_setup_indirect(struct blkfront_info *info);

static int blkfront_gather_backend_features(struct blkfront_info *info);



static int get_id_from_freelist(struct blkfront_info *info)

{
@@ -1525,7 +1526,7 @@ 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;



	rc = blkfront_setup_indirect(info);

	rc = blkfront_gather_backend_features(info);

	if (rc) {

		kfree(copy);

		return rc;
@@ -1726,20 +1727,13 @@ static void blkfront_setup_discard(struct blkfront_info *info) 


static int blkfront_setup_indirect(struct blkfront_info *info)

{

	unsigned int indirect_segments, segs;

	unsigned int segs;

	int err, i;



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

			    "feature-max-indirect-segments", "%u", &indirect_segments,

			    NULL);

	if (err) {

		info->max_indirect_segments = 0;

	if (info->max_indirect_segments == 0)

		segs = BLKIF_MAX_SEGMENTS_PER_REQUEST;

	} else {

		info->max_indirect_segments = min(indirect_segments,

						  xen_blkif_max_segments);

	else

		segs = info->max_indirect_segments;

	}



	err = fill_grant_buffer(info, (segs + INDIRECT_GREFS(segs)) * BLK_RING_SIZE(info));

	if (err)
@@ -1802,6 +1796,68 @@ static int blkfront_setup_indirect(struct blkfront_info *info) 
	return -ENOMEM;

}



/*

 * Gather all backend feature-*

 */

static int blkfront_gather_backend_features(struct blkfront_info *info)

{

	int err;

	int barrier, flush, discard, persistent;

	unsigned int indirect_segments;



	info->feature_flush = 0;



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

			"feature-barrier", "%d", &barrier,

			NULL);



	/*

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

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

	 * synchronously; nothing to do.

	 *

	 * If there are barriers, then we use flush.

	 */

	if (!err && barrier)

		info->feature_flush = REQ_FLUSH | REQ_FUA;

	/*

	 * And if there is "feature-flush-cache" use that above

	 * barriers.

	 */

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

			"feature-flush-cache", "%d", &flush,

			NULL);



	if (!err && flush)

		info->feature_flush = REQ_FLUSH;



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

			"feature-discard", "%d", &discard,

			NULL);



	if (!err && discard)

		blkfront_setup_discard(info);



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

			"feature-persistent", "%u", &persistent,

			NULL);

	if (err)

		info->feature_persistent = 0;

	else

		info->feature_persistent = persistent;



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

			    "feature-max-indirect-segments", "%u", &indirect_segments,

			    NULL);

	if (err)

		info->max_indirect_segments = 0;

	else

		info->max_indirect_segments = min(indirect_segments,

						  xen_blkif_max_segments);



	return blkfront_setup_indirect(info);

}



/*

 * Invoked when the backend is finally 'ready' (and has told produced

 * the details about the physical device - #sectors, size, etc).
@@ -1813,7 +1869,6 @@ static void blkfront_connect(struct blkfront_info *info) 
	unsigned int physical_sector_size;

	unsigned int binfo;

	int err;

	int barrier, flush, discard, persistent;



	switch (info->connected) {

	case BLKIF_STATE_CONNECTED:
@@ -1870,48 +1925,7 @@ static void blkfront_connect(struct blkfront_info *info) 
	if (err != 1)

		physical_sector_size = sector_size;



	info->feature_flush = 0;



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

			    "feature-barrier", "%d", &barrier,

			    NULL);



	/*

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

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

	 * synchronously; nothing to do.

	 *

	 * If there are barriers, then we use flush.

	 */

	if (!err && barrier)

		info->feature_flush = REQ_FLUSH | REQ_FUA;

	/*

	 * And if there is "feature-flush-cache" use that above

	 * barriers.

	 */

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

			    "feature-flush-cache", "%d", &flush,

			    NULL);



	if (!err && flush)

		info->feature_flush = REQ_FLUSH;



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

			    "feature-discard", "%d", &discard,

			    NULL);



	if (!err && discard)

		blkfront_setup_discard(info);



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

			    "feature-persistent", "%u", &persistent,

			    NULL);

	if (err)

		info->feature_persistent = 0;

	else

		info->feature_persistent = persistent;



	err = blkfront_setup_indirect(info);

	err = blkfront_gather_backend_features(info);

	if (err) {

		xenbus_dev_fatal(info->xbdev, err, "setup_indirect at %s",

				 info->xbdev->otherend);