Message ID | 1447039178-17208-1-git-send-email-arei.gonglei@huawei.com |
---|---|
State | New |
Headers | show |
On Mon, 11/09 11:19, arei.gonglei@huawei.com wrote: > From: Gonglei <arei.gonglei@huawei.com> > > 1. avoid possible superflous checking > 2. make code more robustness > > Signed-off-by: Gonglei <arei.gonglei@huawei.com> > --- > v2: address Paolo's comments, thanks. > --- > hw/block/virtio-blk.c | 27 +++++++++------------------ > 1 file changed, 9 insertions(+), 18 deletions(-) > > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > index 093e475..21f8d72 100644 > --- a/hw/block/virtio-blk.c > +++ b/hw/block/virtio-blk.c > @@ -404,24 +404,15 @@ void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb) > for (i = 0; i < mrb->num_reqs; i++) { > VirtIOBlockReq *req = mrb->reqs[i]; > if (num_reqs > 0) { > - bool merge = true; > - > - /* merge would exceed maximum number of IOVs */ > - if (niov + req->qiov.niov > IOV_MAX) { > - merge = false; > - } > - > - /* merge would exceed maximum transfer length of backend device */ > - if (req->qiov.size / BDRV_SECTOR_SIZE + nb_sectors > max_xfer_len) { > - merge = false; > - } > - > - /* requests are not sequential */ > - if (sector_num + nb_sectors != req->sector_num) { > - merge = false; > - } > - > - if (!merge) { > + /* > + * NOTE: We cannot merge the requests in below situations: > + * 1. requests are not sequential > + * 2. merge would exceed maximum number of IOVs > + * 3. merge would exceed maximum transfer length of backend device > + */ > + if (sector_num + nb_sectors != req->sector_num || > + niov > IOV_MAX - req->qiov.niov || > + req->qiov.size / BDRV_SECTOR_SIZE + nb_sectors > max_xfer_len) { > submit_requests(blk, mrb, start, num_reqs, niov); > num_reqs = 0; > } > -- > 1.7.12.4 > > > Reviewed-by: Fam Zheng <famz@redhat.com>
On 09/11/2015 04:19, arei.gonglei@huawei.com wrote: > + * 1. requests are not sequential > + * 2. merge would exceed maximum number of IOVs > + * 3. merge would exceed maximum transfer length of backend device > + */ > + if (sector_num + nb_sectors != req->sector_num || > + niov > IOV_MAX - req->qiov.niov || > + req->qiov.size / BDRV_SECTOR_SIZE + nb_sectors > max_xfer_len) { Hi Gonglei, the third condition should also be changed to "new > max - old". Thanks, Paolo
On 2015/11/9 16:41, Paolo Bonzini wrote: > > > On 09/11/2015 04:19, arei.gonglei@huawei.com wrote: >> + * 1. requests are not sequential >> + * 2. merge would exceed maximum number of IOVs >> + * 3. merge would exceed maximum transfer length of backend device >> + */ >> + if (sector_num + nb_sectors != req->sector_num || >> + niov > IOV_MAX - req->qiov.niov || >> + req->qiov.size / BDRV_SECTOR_SIZE + nb_sectors > max_xfer_len) { > > Hi Gonglei, > > the third condition should also be changed to "new > max - old". > Okay, will do. :) Thanks, -Gonglei
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 093e475..21f8d72 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -404,24 +404,15 @@ void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb) for (i = 0; i < mrb->num_reqs; i++) { VirtIOBlockReq *req = mrb->reqs[i]; if (num_reqs > 0) { - bool merge = true; - - /* merge would exceed maximum number of IOVs */ - if (niov + req->qiov.niov > IOV_MAX) { - merge = false; - } - - /* merge would exceed maximum transfer length of backend device */ - if (req->qiov.size / BDRV_SECTOR_SIZE + nb_sectors > max_xfer_len) { - merge = false; - } - - /* requests are not sequential */ - if (sector_num + nb_sectors != req->sector_num) { - merge = false; - } - - if (!merge) { + /* + * NOTE: We cannot merge the requests in below situations: + * 1. requests are not sequential + * 2. merge would exceed maximum number of IOVs + * 3. merge would exceed maximum transfer length of backend device + */ + if (sector_num + nb_sectors != req->sector_num || + niov > IOV_MAX - req->qiov.niov || + req->qiov.size / BDRV_SECTOR_SIZE + nb_sectors > max_xfer_len) { submit_requests(blk, mrb, start, num_reqs, niov); num_reqs = 0; }