From f4d38bef7cc79018e2aa789b0e4c23c3a8cdfca5 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Mon, 15 Apr 2013 17:17:31 +0200 Subject: [PATCH] qcow2: allow sub-cluster compressed write to last cluster Compression in qcow2 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. Signed-off-by: Stefan Hajnoczi Signed-off-by: Kevin Wolf --- block/qcow2.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index e8934de185..2e346d8c42 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1537,8 +1537,21 @@ static int qcow2_write_compressed(BlockDriverState *bs, int64_t sector_num, return 0; } - 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 = qcow2_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);