virtio_scsi: don't call virtqueue_add_sgs(... GFP_NOIO) holding spinlock.

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

1 files changed, 6 insertions, 9 deletions

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index 16bfd50cd3fe..e2a68aece3da 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 = ∁
         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);