Message ID | 20150402162601.GL15412@fam-t430.nay.redhat.com |
---|---|
State | New |
Headers | show |
On 02/04/2015 18:26, Fam Zheng wrote: > There is another problem with your patch - read_size is not initialized in > non-RW paths like scsi and flush. Right, but... > I think the optimization for write is a separate thing, though. Shouldn't below > patch already fix the migration issue? ... it also doesn't cover SCSI, does it? Paolo
On 04/03/2015 12:26 AM, Fam Zheng wrote: > On Thu, 04/02 17:21, Paolo Bonzini wrote: >> >> >> On 02/04/2015 17:16, Fam Zheng wrote: >>>>>>>>> After qemu_iovec_destroy, the QEMUIOVector's size is zeroed and >>>>>>>>> the zero size ultimately is used to compute virtqueue_push's len >>>>>>>>> argument. Therefore, reads from virtio-blk devices did not >>>>>>>>> migrate their results correctly. (Writes were okay). >>>>>>> >>>>>>> Can't we move qemu_iovec_destroy to virtio_blk_free_request? >>>>> >>>>> You would still have to add more code to differentiate reads and >>>>> writes---I think. >>> Yeah, but the extra field will not be needed. >> >> Can you post an alternative patch? One small complication is that >> is_write is in mrb but not in mrb->reqs[x]. virtio_blk_rw_complete is >> already doing >> >> int p = virtio_ldl_p(VIRTIO_DEVICE(req->dev), &req->out.type); >> bool is_read = !(p & VIRTIO_BLK_T_OUT); >> >> but only in a slow path. > > OK, so it looks like a new field is the simplest way to achieve. > > There is another problem with your patch - read_size is not initialized in > non-RW paths like scsi and flush. > > I think the optimization for write is a separate thing, though. Shouldn't below > patch already fix the migration issue? > > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > index 000c38d..ee6e198 100644 > --- a/hw/block/virtio-blk.c > +++ b/hw/block/virtio-blk.c > @@ -92,13 +92,6 @@ static void virtio_blk_rw_complete(void *opaque, int ret) > next = req->mr_next; > trace_virtio_blk_rw_complete(req, ret); > > - if (req->qiov.nalloc != -1) { > - /* If nalloc is != 1 req->qiov is a local copy of the original > - * external iovec. It was allocated in submit_merged_requests > - * to be able to merge requests. */ > - qemu_iovec_destroy(&req->qiov); > - } > - > if (ret) { > int p = virtio_ldl_p(VIRTIO_DEVICE(req->dev), &req->out.type); > bool is_read = !(p & VIRTIO_BLK_T_OUT); > @@ -109,6 +102,13 @@ static void virtio_blk_rw_complete(void *opaque, int ret) > > virtio_blk_req_complete(req, VIRTIO_BLK_S_OK); > block_acct_done(blk_get_stats(req->dev->blk), &req->acct); > + > + if (req->qiov.nalloc != -1) { > + /* This means req->qiov is a local copy of the original external > + * iovec. It was allocated in virtio_blk_submit_multireq in order > + * to merge requests. */ > + qemu_iovec_destroy(&req->qiov); > + } We will not come here on I/O failure. It will cause memory leak. Thanks Wen Congyang > virtio_blk_free_request(req); > } > } > > > . >
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 000c38d..ee6e198 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -92,13 +92,6 @@ static void virtio_blk_rw_complete(void *opaque, int ret) next = req->mr_next; trace_virtio_blk_rw_complete(req, ret); - if (req->qiov.nalloc != -1) { - /* If nalloc is != 1 req->qiov is a local copy of the original - * external iovec. It was allocated in submit_merged_requests - * to be able to merge requests. */ - qemu_iovec_destroy(&req->qiov); - } - if (ret) { int p = virtio_ldl_p(VIRTIO_DEVICE(req->dev), &req->out.type); bool is_read = !(p & VIRTIO_BLK_T_OUT); @@ -109,6 +102,13 @@ static void virtio_blk_rw_complete(void *opaque, int ret) virtio_blk_req_complete(req, VIRTIO_BLK_S_OK); block_acct_done(blk_get_stats(req->dev->blk), &req->acct); + + if (req->qiov.nalloc != -1) { + /* This means req->qiov is a local copy of the original external + * iovec. It was allocated in virtio_blk_submit_multireq in order + * to merge requests. */ + qemu_iovec_destroy(&req->qiov); + } virtio_blk_free_request(req); } }