virtio_blk: don't crash, report error if virtqueue is broken.

A bad implementation of virtio might cause us to mark the virtqueue
broken: we'll dev_err() in that case, and the device is useless, but
let's not BUG_ON().

ENOMEM or ENOSPC implies the ring is full, and we should try again
later (-ENOMEM is documented to happen, but doesn't, as we fall
through to ENOSPC).

EIO means it's broken.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index b1cb3f4c4db4..a2db9ed288f2 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -158,6 +158,7 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
         unsigned long flags;
         unsigned int num;
         const bool last = (req->cmd_flags & REQ_END) != 0;
+        int err;
 
         BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
 
@@ -198,11 +199,16 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
         }
 
         spin_lock_irqsave(&vblk->vq_lock, flags);
-        if (__virtblk_add_req(vblk->vq, vbr, vbr->sg, num) < 0) {
+        err = __virtblk_add_req(vblk->vq, vbr, vbr->sg, num);
+        if (err) {
                 virtqueue_kick(vblk->vq);
                 spin_unlock_irqrestore(&vblk->vq_lock, flags);
                 blk_mq_stop_hw_queue(hctx);
-                return BLK_MQ_RQ_QUEUE_BUSY;
+                /* Out of mem doesn't actually happen, since we fall back
+                 * to direct descriptors */
+                if (err == -ENOMEM || err == -ENOSPC)
+                        return BLK_MQ_RQ_QUEUE_BUSY;
+                return BLK_MQ_RQ_QUEUE_ERROR;
         }
 
         if (last)