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authorStefan Hajnoczi <stefanha@redhat.com>2013-04-15 17:17:32 +0200
committerKevin Wolf <kwolf@redhat.com>2013-04-22 10:27:58 +0200
commit16b3c5cd9f27678bc9d6707664640653b47533b9 (patch)
treef651cee5296cf7f98e270b87854dda286b40c43d /block
parentf4d38bef7cc79018e2aa789b0e4c23c3a8cdfca5 (diff)
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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>
Diffstat (limited to 'block')
-rw-r--r--block/qcow.c17
1 files changed, 15 insertions, 2 deletions
diff --git a/block/qcow.c b/block/qcow.c
index 3278e55..e2a64c7 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -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);