Re: [PATCH] virtio_scsi: don't call virtqueue_add_sgs(... GFP_NOIO) holding spinlock.

[Paolo Bonzini <pbonzini@redhat.com>]

Il 20/05/2014 07:12, Rusty Russell ha scritto:
> This triggers every time we do a SCSI abort:
>
> virtscsi_tmf -> virtscsi_kick_cmd (grab lock and call) -> virtscsi_add_cmd
> 	-> virtqueue_add_sgs (GFP_NOIO)
>
> Logs look like this:
>  sd 0:0:0:0: [sda] abort
>  BUG: sleeping function called from invalid context at mm/slub.c:966
>  in_atomic(): 1, irqs_disabled(): 1, pid: 6, name: kworker/u2:0
>  3 locks held by kworker/u2:0/6:
>   #0:  ("scsi_tmf_%d"shost->host_no){......}, at: [<c0153180>] process_one_work+0xe0/0x3d0
>   #1:  ((&(&cmd->abort_work)->work)){......}, at: [<c0153180>] process_one_work+0xe0/0x3d0
>   #2:  (&(&virtscsi_vq->vq_lock)->rlock){......}, at: [<c043f508>] virtscsi_kick_cmd+0x18/0x1b0
>  CPU: 0 PID: 6 Comm: kworker/u2:0 Not tainted 3.15.0-rc5+ #110
>  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-rc1-0-gb1d4dc9-20140515_140003-nilsson.home.kraxel.org 04/01/2014
>  Workqueue: scsi_tmf_0 scmd_eh_abort_handler
>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
>
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index db3b494e5926..62757afd93bb 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -433,11 +433,10 @@ static void virtscsi_event_done(struct virtqueue *vq)
>   * @cmd		: command structure
>   * @req_size	: size of the request buffer
>   * @resp_size	: size of the response buffer
> - * @gfp	: flags to use for memory allocations
>   */
>  static int virtscsi_add_cmd(struct virtqueue *vq,
>  			    struct virtio_scsi_cmd *cmd,
> -			    size_t req_size, size_t resp_size, gfp_t gfp)
> +			    size_t req_size, size_t resp_size)
>  {
>  	struct scsi_cmnd *sc = cmd->sc;
>  	struct scatterlist *sgs[4], req, resp;
> @@ -469,19 +468,19 @@ static int virtscsi_add_cmd(struct virtqueue *vq,
>  	if (in)
>  		sgs[out_num + in_num++] = in->sgl;
>
> -	return virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, gfp);
> +	return virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, GFP_ATOMIC);
>  }
>
>  static int virtscsi_kick_cmd(struct virtio_scsi_vq *vq,
>  			     struct virtio_scsi_cmd *cmd,
> -			     size_t req_size, size_t resp_size, gfp_t gfp)
> +			     size_t req_size, size_t resp_size)
>  {
>  	unsigned long flags;
>  	int err;
>  	bool needs_kick = false;
>
>  	spin_lock_irqsave(&vq->vq_lock, flags);
> -	err = virtscsi_add_cmd(vq->vq, cmd, req_size, resp_size, gfp);
> +	err = virtscsi_add_cmd(vq->vq, cmd, req_size, resp_size);
>  	if (!err)
>  		needs_kick = virtqueue_kick_prepare(vq->vq);
>
> @@ -530,8 +529,7 @@ static int virtscsi_queuecommand(struct virtio_scsi *vscsi,
>  	memcpy(cmd->req.cmd.cdb, sc->cmnd, sc->cmd_len);
>
>  	if (virtscsi_kick_cmd(req_vq, cmd,
> -			      sizeof cmd->req.cmd, sizeof cmd->resp.cmd,
> -			      GFP_ATOMIC) == 0)
> +			      sizeof cmd->req.cmd, sizeof cmd->resp.cmd) == 0)
>  		ret = 0;
>  	else
>  		mempool_free(cmd, virtscsi_cmd_pool);
> @@ -596,8 +594,7 @@ static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
>
>  	cmd->comp = &comp;
>  	if (virtscsi_kick_cmd(&vscsi->ctrl_vq, cmd,
> -			      sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
> -			      GFP_NOIO) < 0)
> +			      sizeof cmd->req.tmf, sizeof cmd->resp.tmf) < 0)
>  		goto out;
>
>  	wait_for_completion(&comp);
>

Acked-by: Paolo Bonzini <pbonzini@redhat.com>