[Qemu-devel] [PATCH 6/5] block: Fix harmless off-by-one in bdrv_aligned_preadv()

[Eric Blake <eblake@redhat.com>]

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>
---
 block/io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/io.c b/block/io.c
index aaeedaa..c8b323e 100644
--- a/block/io.c
+++ b/block/io.c
@@ -996,7 +996,7 @@ static int coroutine_fn bdrv_aligned_preadv(BlockDriverState *bs,

         max_nb_sectors = ROUND_UP(MAX(0, total_sectors - sector_num),
                                   align >> BDRV_SECTOR_BITS);
-        if (nb_sectors < max_nb_sectors) {
+        if (nb_sectors <= max_nb_sectors) {
             ret = bdrv_driver_preadv(bs, offset, bytes, qiov, flags);
         } else if (max_nb_sectors > 0) {
             QEMUIOVector local_qiov;
-- 
2.5.5