virtio-blk: handle NULL returns from bdrv_aio_{read, write}

PATCH New Christoph Hellwig 1 participant 1 message Aug 13, 2009

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Christoph Hellwig

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2009-08-13 14:50 UTC #0 lore raw

PATCH 1/1 virtio-blk: handle NULL returns from bdrv_aio_{read, write}

The bdrv_aio_{read,write} routines can return a NULL pointer when the I/O submission fails. Currently we ignore this and will wait forever for an I/O completion and leading to a hang of the guest.

I can easily reproduce this using the native Linux AIO patch, but it's also possible using normal pthreads-based AIO.

Signed-off-by Christoph Hellwig <[email protected]>

hw/virtio-blk.c +14 -4

Index: qemu-kvm/hw/virtio-blk.c
===================================================================
@@ -254,14 +254,24 @@ static void virtio_blk_handle_scsi(VirtI
 
 static void virtio_blk_handle_write(VirtIOBlockReq *req)
 {
-    bdrv_aio_writev(req->dev->bs, req->out->sector, &req->qiov,
-                    req->qiov.size / 512, virtio_blk_rw_complete, req);
+    BlockDriverAIOCB *acb;
+
+    acb = bdrv_aio_writev(req->dev->bs, req->out->sector, &req->qiov,
+                          req->qiov.size / 512, virtio_blk_rw_complete, req);
+    if (!acb) {
+        virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
+    }
 }
 
 static void virtio_blk_handle_read(VirtIOBlockReq *req)
 {
-    bdrv_aio_readv(req->dev->bs, req->out->sector, &req->qiov,
-                   req->qiov.size / 512, virtio_blk_rw_complete, req);
+    BlockDriverAIOCB *acb;
+
+    acb = bdrv_aio_readv(req->dev->bs, req->out->sector, &req->qiov,
+                         req->qiov.size / 512, virtio_blk_rw_complete, req);
+    if (!acb) {
+        virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
+    }
 }
 
 static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)