[Qemu-devel] [PATCH for-2.5 v2 3/4] block: replace IOV_MAX with BlockLimits.max_iov

[Stefan Hajnoczi]

Request merging must not result in a huge request that exceeds the
maximum number of iovec elements.  Use BlockLimits.max_iov instead of
hardcoding IOV_MAX.

Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
 block/io.c            | 3 ++-
 hw/block/virtio-blk.c | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/io.c b/block/io.c
index 37bc0dc..66ae770 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1854,7 +1854,8 @@ static int multiwrite_merge(BlockDriverState *bs, 
BlockRequest *reqs,
             merge = 1;
         }
 
-        if (reqs[outidx].qiov->niov + reqs[i].qiov->niov + 1 > IOV_MAX) {
+        if (reqs[outidx].qiov->niov + reqs[i].qiov->niov + 1 >
+            bs->bl.max_iov) {
             merge = 0;
         }
 
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 6aefda4..a186956 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -407,7 +407,7 @@ void virtio_blk_submit_multireq(BlockBackend *blk, 
MultiReqBuffer *mrb)
             bool merge = true;
 
             /* merge would exceed maximum number of IOVs */
-            if (niov + req->qiov.niov > IOV_MAX) {
+            if (niov + req->qiov.niov > blk_get_max_iov(blk)) {
                 merge = false;
             }
 
-- 
2.4.3