[3.13.y.z extended stable] Patch "virtio_blk: don't crash, report error if virtqueue is broken." has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 4d197b0e9421ee3a5fdfe0d995c8999fb7ce55b5 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty at rustcorp.com.au>
Date: Thu, 13 Mar 2014 11:23:39 +1030
Subject: virtio_blk: don't crash, report error if virtqueue is broken.

commit 5261b85e586afe6ebe54e16e0a8acc32fc6d4902 upstream.

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 at rustcorp.com.au>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/block/virtio_blk.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 6a680d4..704d6c8 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)
--
1.9.1