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qcow2: simplify logic in qcow2_co_write_zeroes

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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: Denis V. Lunev <den@openvz.org>
Reviewed-by: Eric 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: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Denis V. Lunev 2016-05-25 21:48:46 -06:00 committed by Kevin Wolf
parent 443668ca40
commit ba142846b0
1 changed files with 5 additions and 18 deletions
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23
block/qcow2.c
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@ -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;
}