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 <ebl...@redhat.com> Reviewed-by: Kevin Wolf <kw...@redhat.com> Reviewed-by: Fam Zheng <f...@redhat.com> Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com> --- v3: no change v2: no change, add R-b --- block/io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/io.c b/block/io.c index 994d3fa..82c9ff0 100644 --- a/block/io.c +++ b/block/io.c @@ -1036,7 +1036,7 @@ 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; -- 2.5.5