virtio-blk: Bypass error action and I/O accounting on invalid r/w

When a device model's I/O operation fails, we execute the error
action.  This lets layers above QEMU implement thin provisioning, or
attempt to correct errors before they reach the guest.  But when the
I/O operation fails because it's invalid, reporting the error to the
guest is the only sensible action.

If the guest's read or write asks for an invalid sector range, fail
the request right away, without considering the error action.  No
change with error action BDRV_ACTION_REPORT.

Furthermore, bypass I/O accounting, because we want to track only I/O
that actually reaches the block layer.

The next commit will extend "invalid sector range" to cover attempts
to read/write beyond the end of the medium.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 075e6e626f5786110cc578d7a8c6991e211c43d4..e6e62768e4d5c2b13c6b53ba7054bf0128ce792f 100644 (file)
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -307,15 +307,16 @@ static void virtio_blk_handle_write(VirtIOBlockReq *req, MultiReqBuffer *mrb)
 
     sector = virtio_ldq_p(VIRTIO_DEVICE(req->dev), &req->out.sector);
 
-    bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_WRITE);
-
     trace_virtio_blk_handle_write(req, sector, req->qiov.size / 512);
 
     if (!virtio_blk_sect_range_ok(req->dev, sector, req->qiov.size)) {
-        virtio_blk_rw_complete(req, -EIO);
+        virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
+        virtio_blk_free_request(req);
         return;
     }
 
+    bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_WRITE);
+
     if (mrb->num_writes == 32) {
         virtio_submit_multiwrite(req->dev->bs, mrb);
     }
@@ -337,14 +338,15 @@ static void virtio_blk_handle_read(VirtIOBlockReq *req)
 
     sector = virtio_ldq_p(VIRTIO_DEVICE(req->dev), &req->out.sector);
 
-    bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_READ);
-
     trace_virtio_blk_handle_read(req, sector, req->qiov.size / 512);
 
     if (!virtio_blk_sect_range_ok(req->dev, sector, req->qiov.size)) {
-        virtio_blk_rw_complete(req, -EIO);
+        virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
+        virtio_blk_free_request(req);
         return;
     }
+
+    bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_READ);
     bdrv_aio_readv(req->dev->bs, sector, &req->qiov,
                    req->qiov.size / BDRV_SECTOR_SIZE,
                    virtio_blk_rw_complete, req);