Re: FAILED: patch "[PATCH] virtio_ring: fix return code on DMA mapping fails" failed to apply to 4.19-stable tree

[Sasha Levin <sashal@kernel.org>]

On Mon, Nov 25, 2019 at 06:44:26PM +0100, gregkh@linuxfoundation.org wrote:
>
>The patch below does not apply to the 4.19-stable tree.
>If someone wants it applied there, or to any other stable or longterm
>tree, then please email the backport, including the original git commit
>id to <stable@vger.kernel.org>.
>
>thanks,
>
>greg k-h
>
>------------------ original commit in Linus's tree ------------------
>
>From f7728002c1c7bfa787b276a31c3ef458739b8e7c Mon Sep 17 00:00:00 2001
>From: Halil Pasic <pasic@linux.ibm.com>
>Date: Thu, 14 Nov 2019 13:46:46 +0100
>Subject: [PATCH] virtio_ring: fix return code on DMA mapping fails
>
>Commit 780bc7903a32 ("virtio_ring: Support DMA APIs")  makes
>virtqueue_add() return -EIO when we fail to map our I/O buffers. This is
>a very realistic scenario for guests with encrypted memory, as swiotlb
>may run out of space, depending on it's size and the I/O load.
>
>The virtio-blk driver interprets -EIO form virtqueue_add() as an IO
>error, despite the fact that swiotlb full is in absence of bugs a
>recoverable condition.
>
>Let us change the return code to -ENOMEM, and make the block layer
>recover form these failures when virtio-blk encounters the condition
>described above.
>
>Cc: stable@vger.kernel.org
>Fixes: 780bc7903a32 ("virtio_ring: Support DMA APIs")
>Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
>Tested-by: Michael Mueller <mimu@linux.ibm.com>
>Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

The code got shuffled around a bit in 138fd2514863 ("virtio_ring: add
_split suffix for split ring functions"), I've cleaned it up and queued
it for 4.19, 4.14, and 4.9.

-- 
Thanks,
Sasha