We can support PREALLOC_MODE_METADATA by invoking preallocate() in qcow2_truncate().
Signed-off-by: Max Reitz <mre...@redhat.com> --- block/qcow2.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index 5479fed938..5dc95ff0a5 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2531,10 +2531,11 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, PreallocMode prealloc, Error **errp) { BDRVQcow2State *s = bs->opaque; + uint64_t old_length; int64_t new_l1_size; int ret; - if (prealloc != PREALLOC_MODE_OFF) { + if (prealloc != PREALLOC_MODE_OFF && prealloc != PREALLOC_MODE_METADATA) { error_setg(errp, "Unsupported preallocation mode '%s'", PreallocMode_lookup[prealloc]); return -ENOTSUP; @@ -2551,8 +2552,10 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, return -ENOTSUP; } + old_length = bs->total_sectors * 512; + /* shrinking is currently not supported */ - if (offset < bs->total_sectors * 512) { + if (offset < old_length) { error_setg(errp, "qcow2 doesn't support shrinking images yet"); return -ENOTSUP; } @@ -2564,6 +2567,23 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset, return ret; } + switch (prealloc) { + case PREALLOC_MODE_OFF: + break; + + case PREALLOC_MODE_METADATA: + ret = preallocate(bs, old_length, offset); + if (ret < 0) { + error_setg_errno(errp, -ret, "Preallocation failed, image may now " + "occupy more space than necessary"); + return ret; + } + break; + + default: + g_assert_not_reached(); + } + /* write updated header.size */ offset = cpu_to_be64(offset); ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, size), -- 2.12.0