diff mbox

[v2,03/17] block: Fix harmless off-by-one in bdrv_aligned_preadv()

Message ID 1465939839-30097-4-git-send-email-eblake@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Eric Blake June 14, 2016, 9:30 p.m. UTC 
If the amount of data to read ends exactly on the total size
of the bs, then we were wasting time creating a local qiov
to read the data in preparation for what would normally be
appending zeroes beyond the end, even though this corner case
has nothing further to do.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>

---
v2: no change, add R-b
---
 block/io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Fam Zheng June 16, 2016, 5:10 a.m. UTC | #1 
On Tue, 06/14 15:30, Eric Blake wrote:
> If the amount of data to read ends exactly on the total size
> of the bs, then we were wasting time creating a local qiov
> to read the data in preparation for what would normally be
> appending zeroes beyond the end, even though this corner case
> has nothing further to do.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: Kevin Wolf <kwolf@redhat.com>

Reviewed-by: Fam Zheng <famz@redhat.com>
Stefan Hajnoczi June 20, 2016, 12:12 p.m. UTC | #2 
On Tue, Jun 14, 2016 at 03:30:25PM -0600, Eric Blake wrote:
> If the amount of data to read ends exactly on the total size
> of the bs, then we were wasting time creating a local qiov
> to read the data in preparation for what would normally be
> appending zeroes beyond the end, even though this corner case
> has nothing further to do.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: Kevin Wolf <kwolf@redhat.com>
> 
> ---
> v2: no change, add R-b
> ---
>  block/io.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
diff mbox

Patch

diff --git a/block/io.c b/block/io.c
index 9191772..383154f 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1024,7 +1024,7 @@  static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,
     }

     max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
-    if (bytes < max_bytes) {
+    if (bytes <= max_bytes) {
         ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0);
     } else if (max_bytes > 0) {
         QEMUIOVector local_qiov;