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Commit b647c449 authored by Juergen Gross's avatar Juergen Gross Committed by Greg Kroah-Hartman
Browse files

xen/blkfront: read response from backend only once 



commit 71b66243f9898d0e54296b4e7035fb33cdcb0707 upstream.

In order to avoid problems in case the backend is modifying a response
on the ring page while the frontend has already seen it, just read the
response into a local buffer in one go and then operate on that buffer
only.

Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarJan Beulich <jbeulich@suse.com>
Acked-by: default avatarRoger Pau Monné <roger.pau@citrix.com>
Link: https://lore.kernel.org/r/20210730103854.12681-2-jgross@suse.com


Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent dcbfd3f1

drivers/block/xen-blkfront.c

+18 −17
Original line number Diff line number Diff line
@@ -1549,7 +1549,7 @@ static bool blkif_completion(unsigned long *id, 
static irqreturn_t blkif_interrupt(int irq, void *dev_id)

{

	struct request *req;

	struct blkif_response *bret;

	struct blkif_response bret;

	RING_IDX i, rp;

	unsigned long flags;

	struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)dev_id;
@@ -1566,8 +1566,9 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) 
	for (i = rinfo->ring.rsp_cons; i != rp; i++) {

		unsigned long id;



		bret = RING_GET_RESPONSE(&rinfo->ring, i);

		id   = bret->id;

		RING_COPY_RESPONSE(&rinfo->ring, i, &bret);

		id = bret.id;



		/*

		 * The backend has messed up and given us an id that we would

		 * never have given to it (we stamp it up to BLK_RING_SIZE -
@@ -1575,39 +1576,39 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) 
		 */

		if (id >= BLK_RING_SIZE(info)) {

			WARN(1, "%s: response to %s has incorrect id (%ld)\n",

			     info->gd->disk_name, op_name(bret->operation), id);

			     info->gd->disk_name, op_name(bret.operation), id);

			/* We can't safely get the 'struct request' as

			 * the id is busted. */

			continue;

		}

		req  = rinfo->shadow[id].request;



		if (bret->operation != BLKIF_OP_DISCARD) {

		if (bret.operation != BLKIF_OP_DISCARD) {

			/*

			 * We may need to wait for an extra response if the

			 * I/O request is split in 2

			 */

			if (!blkif_completion(&id, rinfo, bret))

			if (!blkif_completion(&id, rinfo, &bret))

				continue;

		}



		if (add_id_to_freelist(rinfo, id)) {

			WARN(1, "%s: response to %s (id %ld) couldn't be recycled!\n",

			     info->gd->disk_name, op_name(bret->operation), id);

			     info->gd->disk_name, op_name(bret.operation), id);

			continue;

		}



		if (bret->status == BLKIF_RSP_OKAY)

		if (bret.status == BLKIF_RSP_OKAY)

			blkif_req(req)->error = BLK_STS_OK;

		else

			blkif_req(req)->error = BLK_STS_IOERR;



		switch (bret->operation) {

		switch (bret.operation) {

		case BLKIF_OP_DISCARD:

			if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {

			if (unlikely(bret.status == BLKIF_RSP_EOPNOTSUPP)) {

				struct request_queue *rq = info->rq;

				printk(KERN_WARNING "blkfront: %s: %s op failed\n",

					   info->gd->disk_name, op_name(bret->operation));

					   info->gd->disk_name, op_name(bret.operation));

				blkif_req(req)->error = BLK_STS_NOTSUPP;

				info->feature_discard = 0;

				info->feature_secdiscard = 0;
@@ -1617,15 +1618,15 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) 
			break;

		case BLKIF_OP_FLUSH_DISKCACHE:

		case BLKIF_OP_WRITE_BARRIER:

			if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {

			if (unlikely(bret.status == BLKIF_RSP_EOPNOTSUPP)) {

				printk(KERN_WARNING "blkfront: %s: %s op failed\n",

				       info->gd->disk_name, op_name(bret->operation));

				       info->gd->disk_name, op_name(bret.operation));

				blkif_req(req)->error = BLK_STS_NOTSUPP;

			}

			if (unlikely(bret->status == BLKIF_RSP_ERROR &&

			if (unlikely(bret.status == BLKIF_RSP_ERROR &&

				     rinfo->shadow[id].req.u.rw.nr_segments == 0)) {

				printk(KERN_WARNING "blkfront: %s: empty %s op failed\n",

				       info->gd->disk_name, op_name(bret->operation));

				       info->gd->disk_name, op_name(bret.operation));

				blkif_req(req)->error = BLK_STS_NOTSUPP;

			}

			if (unlikely(blkif_req(req)->error)) {
@@ -1638,9 +1639,9 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) 
			/* fall through */

		case BLKIF_OP_READ:

		case BLKIF_OP_WRITE:

			if (unlikely(bret->status != BLKIF_RSP_OKAY))

			if (unlikely(bret.status != BLKIF_RSP_OKAY))

				dev_dbg(&info->xbdev->dev, "Bad return from blkdev data "

					"request: %x\n", bret->status);

					"request: %x\n", bret.status);



			break;

		default: