[Qemu-devel] [PATCH 2/2] virtio-blk: Use blk_aio_ioctl

[Fam Zheng]

Use the asynchronous interface of ioctl. This will not make the VM
unresponsive if the ioctl takes a long time.

Signed-off-by: Fam Zheng <address@hidden>
---
 hw/block/virtio-blk.c | 125 +++++++++++++++++++++++++++++++-------------------
 1 file changed, 79 insertions(+), 46 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 60cb1d8..4032fca 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -115,6 +115,56 @@ static void virtio_blk_flush_complete(void *opaque, int 
ret)
     virtio_blk_free_request(req);
 }
 
+#ifdef __linux__
+
+typedef struct {
+    VirtIOBlockReq *req;
+    struct sg_io_hdr hdr;
+} VirtIOBlockIoctlReq;
+
+static void virtio_blk_ioctl_complete(void *opaque, int status)
+{
+    VirtIOBlockIoctlReq *ioctl_req = opaque;
+    VirtIOBlockReq *req = ioctl_req->req;
+    VirtIODevice *vdev = VIRTIO_DEVICE(req->dev);
+    struct virtio_scsi_inhdr *scsi;
+    struct sg_io_hdr *hdr;
+
+    scsi = (void *)req->elem.in_sg[req->elem.in_num - 2].iov_base;
+
+    if (status) {
+        status = VIRTIO_BLK_S_UNSUPP;
+        virtio_stl_p(vdev, &scsi->errors, 255);
+        goto out;
+    }
+
+    hdr = &ioctl_req->hdr;
+    /*
+     * From SCSI-Generic-HOWTO: "Some lower level drivers (e.g. ide-scsi)
+     * clear the masked_status field [hence status gets cleared too, see
+     * block/scsi_ioctl.c] even when a CHECK_CONDITION or COMMAND_TERMINATED
+     * status has occurred.  However they do set DRIVER_SENSE in driver_status
+     * field. Also a (sb_len_wr > 0) indicates there is a sense buffer.
+     */
+    if (hdr->status == 0 && hdr->sb_len_wr > 0) {
+        hdr->status = CHECK_CONDITION;
+    }
+
+    virtio_stl_p(vdev, &scsi->errors,
+                 hdr->status | (hdr->msg_status << 8) |
+                 (hdr->host_status << 16) | (hdr->driver_status << 24));
+    virtio_stl_p(vdev, &scsi->residual, hdr->resid);
+    virtio_stl_p(vdev, &scsi->sense_len, hdr->sb_len_wr);
+    virtio_stl_p(vdev, &scsi->data_len, hdr->dxfer_len);
+
+out:
+    virtio_blk_req_complete(req, status);
+    virtio_blk_free_request(req);
+    g_free(ioctl_req);
+}
+
+#endif
+
 static VirtIOBlockReq *virtio_blk_get_request(VirtIOBlock *s)
 {
     VirtIOBlockReq *req = virtio_blk_alloc_request(s);
@@ -137,7 +187,7 @@ static int virtio_blk_handle_scsi_req(VirtIOBlockReq *req)
 
 #ifdef __linux__
     int i;
-    struct sg_io_hdr hdr;
+    VirtIOBlockIoctlReq *ioctl_req;
 #endif
 
     /*
@@ -172,71 +222,52 @@ static int virtio_blk_handle_scsi_req(VirtIOBlockReq *req)
     }
 
 #ifdef __linux__
-    memset(&hdr, 0, sizeof(struct sg_io_hdr));
-    hdr.interface_id = 'S';
-    hdr.cmd_len = elem->out_sg[1].iov_len;
-    hdr.cmdp = elem->out_sg[1].iov_base;
-    hdr.dxfer_len = 0;
+    ioctl_req = g_new0(VirtIOBlockIoctlReq, 1);
+    ioctl_req->req = req;
+    ioctl_req->hdr.interface_id = 'S';
+    ioctl_req->hdr.cmd_len = elem->out_sg[1].iov_len;
+    ioctl_req->hdr.cmdp = elem->out_sg[1].iov_base;
+    ioctl_req->hdr.dxfer_len = 0;
 
     if (elem->out_num > 2) {
         /*
          * If there are more than the minimally required 2 output segments
          * there is write payload starting from the third iovec.
          */
-        hdr.dxfer_direction = SG_DXFER_TO_DEV;
-        hdr.iovec_count = elem->out_num - 2;
+        ioctl_req->hdr.dxfer_direction = SG_DXFER_TO_DEV;
+        ioctl_req->hdr.iovec_count = elem->out_num - 2;
 
-        for (i = 0; i < hdr.iovec_count; i++)
-            hdr.dxfer_len += elem->out_sg[i + 2].iov_len;
+        for (i = 0; i < ioctl_req->hdr.iovec_count; i++) {
+            ioctl_req->hdr.dxfer_len += elem->out_sg[i + 2].iov_len;
+        }
 
-        hdr.dxferp = elem->out_sg + 2;
+        ioctl_req->hdr.dxferp = elem->out_sg + 2;
 
     } else if (elem->in_num > 3) {
         /*
          * If we have more than 3 input segments the guest wants to actually
          * read data.
          */
-        hdr.dxfer_direction = SG_DXFER_FROM_DEV;
-        hdr.iovec_count = elem->in_num - 3;
-        for (i = 0; i < hdr.iovec_count; i++)
-            hdr.dxfer_len += elem->in_sg[i].iov_len;
+        ioctl_req->hdr.dxfer_direction = SG_DXFER_FROM_DEV;
+        ioctl_req->hdr.iovec_count = elem->in_num - 3;
+        for (i = 0; i < ioctl_req->hdr.iovec_count; i++) {
+            ioctl_req->hdr.dxfer_len += elem->in_sg[i].iov_len;
+        }
 
-        hdr.dxferp = elem->in_sg;
+        ioctl_req->hdr.dxferp = elem->in_sg;
     } else {
         /*
          * Some SCSI commands don't actually transfer any data.
          */
-        hdr.dxfer_direction = SG_DXFER_NONE;
+        ioctl_req->hdr.dxfer_direction = SG_DXFER_NONE;
     }
 
-    hdr.sbp = elem->in_sg[elem->in_num - 3].iov_base;
-    hdr.mx_sb_len = elem->in_sg[elem->in_num - 3].iov_len;
-
-    status = blk_ioctl(blk->blk, SG_IO, &hdr);
-    if (status) {
-        status = VIRTIO_BLK_S_UNSUPP;
-        goto fail;
-    }
+    ioctl_req->hdr.sbp = elem->in_sg[elem->in_num - 3].iov_base;
+    ioctl_req->hdr.mx_sb_len = elem->in_sg[elem->in_num - 3].iov_len;
 
-    /*
-     * From SCSI-Generic-HOWTO: "Some lower level drivers (e.g. ide-scsi)
-     * clear the masked_status field [hence status gets cleared too, see
-     * block/scsi_ioctl.c] even when a CHECK_CONDITION or COMMAND_TERMINATED
-     * status has occurred.  However they do set DRIVER_SENSE in driver_status
-     * field. Also a (sb_len_wr > 0) indicates there is a sense buffer.
-     */
-    if (hdr.status == 0 && hdr.sb_len_wr > 0) {
-        hdr.status = CHECK_CONDITION;
-    }
-
-    virtio_stl_p(vdev, &scsi->errors,
-                 hdr.status | (hdr.msg_status << 8) |
-                 (hdr.host_status << 16) | (hdr.driver_status << 24));
-    virtio_stl_p(vdev, &scsi->residual, hdr.resid);
-    virtio_stl_p(vdev, &scsi->sense_len, hdr.sb_len_wr);
-    virtio_stl_p(vdev, &scsi->data_len, hdr.dxfer_len);
-
-    return status;
+    blk_aio_ioctl(blk->blk, SG_IO, &ioctl_req->hdr,
+                  virtio_blk_ioctl_complete, ioctl_req);
+    return -EINPROGRESS;
 #else
     abort();
 #endif
@@ -254,8 +285,10 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
     int status;
 
     status = virtio_blk_handle_scsi_req(req);
-    virtio_blk_req_complete(req, status);
-    virtio_blk_free_request(req);
+    if (status != -EINPROGRESS) {
+        virtio_blk_req_complete(req, status);
+        virtio_blk_free_request(req);
+    }
 }
 
 void virtio_submit_multiwrite(BlockBackend *blk, MultiReqBuffer *mrb)
-- 
1.9.3