Commit ba142846 authored by Denis V. Lunev's avatar Denis V. Lunev Committed by Kevin Wolf
Browse files

qcow2: simplify logic in qcow2_co_write_zeroes 



Unaligned requests will occupy only one cluster. This is true since the
previous commit. Simplify the code taking this consideration into
account.

In other words, the caller is now buggy if it ever passes us an unaligned
request that crosses cluster boundaries (the only requests that can cross
boundaries will be aligned).

There are no other changes so far.

Signed-off-by: default avatarDenis V. Lunev <den@openvz.org>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
Message-Id: <1463476543-3087-3-git-send-email-den@openvz.org>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 443668ca

block/qcow2.c

+5 −18
Original line number Diff line number Diff line
@@ -2438,33 +2438,20 @@ static coroutine_fn int qcow2_co_write_zeroes(BlockDriverState *bs, 
    int tail = (sector_num + nb_sectors) % s->cluster_sectors;



    if (head != 0 || tail != 0) {

        int64_t cl_end = -1;

        int64_t cl_start = sector_num - head;



        sector_num -= head;

        nb_sectors += head;

        assert(cl_start + s->cluster_sectors >= sector_num + nb_sectors);



        if (tail != 0) {

            nb_sectors += s->cluster_sectors - tail;

        }

        sector_num = cl_start;

        nb_sectors = s->cluster_sectors;



        if (!is_zero_cluster(bs, sector_num)) {

            return -ENOTSUP;

        }



        if (nb_sectors > s->cluster_sectors) {

            /* Technically the request can cover 2 clusters, f.e. 4k write

               at s->cluster_sectors - 2k offset. One of these cluster can

               be zeroed, one unallocated */

            cl_end = sector_num + nb_sectors - s->cluster_sectors;

            if (!is_zero_cluster(bs, cl_end)) {

                return -ENOTSUP;

            }

        }



        qemu_co_mutex_lock(&s->lock);

        /* We can have new write after previous check */

        if (!is_zero_cluster_top_locked(bs, sector_num) ||

                (cl_end > 0 && !is_zero_cluster_top_locked(bs, cl_end))) {

        if (!is_zero_cluster_top_locked(bs, sector_num)) {

            qemu_co_mutex_unlock(&s->lock);

            return -ENOTSUP;

        }