Commit 82524274 authored by Eric Blake's avatar Eric Blake Committed by Kevin Wolf
Browse files

block: Fix harmless off-by-one in bdrv_aligned_preadv() 



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: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarFam Zheng <famz@redhat.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent a604fa2b

block/io.c

+1 −1
Original line number Diff line number Diff line
@@ -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;