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qcow: allow sub-cluster compressed write to last cluster 

Compression in qcow requires image length to be a multiple of the
cluster size.  Lift this requirement by zero-padding the final cluster
when necessary.  The virtual disk size is still not cluster-aligned, so
the guest cannot access the zero sectors.

Note that this is almost identical to the qcow2 version of this code.
qcow2's compression code is drawn from qcow.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2013-04-15 17:17:32 +02:00 committed by Kevin Wolf
parent f4d38bef7c
commit 16b3c5cd9f
1 changed files with 15 additions and 2 deletions
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17
block/qcow.c
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@ -787,8 +787,21 @@ static int qcow_write_compressed(BlockDriverState *bs, int64_t sector_num,
uint8_t *out_buf;
uint64_t cluster_offset;
if (nb_sectors != s->cluster_sectors)
return -EINVAL;
if (nb_sectors != s->cluster_sectors) {
ret = -EINVAL;
/* Zero-pad last write if image size is not cluster aligned */
if (sector_num + nb_sectors == bs->total_sectors &&
nb_sectors < s->cluster_sectors) {
uint8_t *pad_buf = qemu_blockalign(bs, s->cluster_size);
memset(pad_buf, 0, s->cluster_size);
memcpy(pad_buf, buf, nb_sectors * BDRV_SECTOR_SIZE);
ret = qcow_write_compressed(bs, sector_num,
pad_buf, s->cluster_sectors);
qemu_vfree(pad_buf);
}
return ret;
}
out_buf = g_malloc(s->cluster_size + (s->cluster_size / 1000) + 128);