virtio_blk: Fix default logical block size fallback

If we fail to read a logical block size in virtblk_read_limits() ->
virtio_cread_feature(), then we default to what is in
lim->logical_block_size, but that would be 0.

We can deal with lim->logical_block_size = 0 later in the
blk_mq_alloc_disk(), but the code in virtblk_read_limits() needs a proper
default, so give a default of SECTOR_SIZE.

Fixes: 27e32cd2 ("block: pass a queue_limits argument to blk_mq_alloc_disk")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20240708091651.177447-2-john.g.garry@oracle.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/virtio_blk.c

@@ -1250,7 +1250,7 @@ static int virtblk_read_limits(struct virtio_blk *vblk,
 		struct queue_limits *lim)
 {
 	struct virtio_device *vdev = vblk->vdev;
-	u32 v, blk_size, max_size, sg_elems, opt_io_size;
+	u32 v, max_size, sg_elems, opt_io_size;
 	u32 max_discard_segs = 0;
 	u32 discard_granularity = 0;
 	u16 min_io_size;
@@ -1291,44 +1291,43 @@ static int virtblk_read_limits(struct virtio_blk *vblk,
 	/* Host can optionally specify the block size of the device */
 	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_BLK_SIZE,
 				   struct virtio_blk_config, blk_size,
-				   &blk_size);
+				   &lim->logical_block_size);
 	if (!err) {
-		err = blk_validate_block_size(blk_size);
+		err = blk_validate_block_size(lim->logical_block_size);
 		if (err) {
 			dev_err(&vdev->dev,
 				"virtio_blk: invalid block size: 0x%x\n",
-				blk_size);
+				lim->logical_block_size);
 			return err;
 		}
-
-		lim->logical_block_size = blk_size;
-	} else
-		blk_size = lim->logical_block_size;
+	}
 
 	/* Use topology information if available */
 	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY,
 				   struct virtio_blk_config, physical_block_exp,
 				   &physical_block_exp);
 	if (!err && physical_block_exp)
-		lim->physical_block_size = blk_size * (1 << physical_block_exp);
+		lim->physical_block_size =
+			lim->logical_block_size * (1 << physical_block_exp);
 
 	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY,
 				   struct virtio_blk_config, alignment_offset,
 				   &alignment_offset);
 	if (!err && alignment_offset)
-		lim->alignment_offset = blk_size * alignment_offset;
+		lim->alignment_offset =
+			lim->logical_block_size * alignment_offset;
 
 	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY,
 				   struct virtio_blk_config, min_io_size,
 				   &min_io_size);
 	if (!err && min_io_size)
-		lim->io_min = blk_size * min_io_size;
+		lim->io_min = lim->logical_block_size * min_io_size;
 
 	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_TOPOLOGY,
 				   struct virtio_blk_config, opt_io_size,
 				   &opt_io_size);
 	if (!err && opt_io_size)
-		lim->io_opt = blk_size * opt_io_size;
+		lim->io_opt = lim->logical_block_size * opt_io_size;
 
 	if (virtio_has_feature(vdev, VIRTIO_BLK_F_DISCARD)) {
 		virtio_cread(vdev, struct virtio_blk_config,
@@ -1422,7 +1421,7 @@ static int virtblk_read_limits(struct virtio_blk *vblk,
 			lim->discard_granularity =
 				discard_granularity << SECTOR_SHIFT;
 		else
-			lim->discard_granularity = blk_size;
+			lim->discard_granularity = lim->logical_block_size;
 	}
 
 	if (virtio_has_feature(vdev, VIRTIO_BLK_F_ZONED)) {
@@ -1453,6 +1452,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 	struct virtio_blk *vblk;
 	struct queue_limits lim = {
 		.features		= BLK_FEAT_ROTATIONAL,
+		.logical_block_size	= SECTOR_SIZE,
 	};
 	int err, index;
 	unsigned int queue_depth;