[ Cc: qemu-block ]
Am 27.03.2017 um 16:38 hat Denis V. Lunev geschrieben:
> Parallels driver should not call bdrv_truncate if the image was opened
> in the read-only mode. Without the patch
> qemu-img check harddisk.hds
> asserts with
> bdrv_truncate: Assertion `child->perm & BLK_PERM_RESIZE' failed.
>
> Parameters used on the write path are not needed if the image is opened
> in the read-only mode.
>
> Signed-off-by: Denis V. Lunev <d...@openvz.org>
> Reported-by: Edgar Kaziahmedov <e...@virtuozzo.mipt.ru>
> CC: Stefan Hajnoczi <stefa...@redhat.com>
> ---
> block/parallels.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/parallels.c b/block/parallels.c
> index 6bf9375..4173b3f 100644
> --- a/block/parallels.c
> +++ b/block/parallels.c
> @@ -687,7 +687,8 @@ static int parallels_open(BlockDriverState *bs, QDict
> *options, int flags,
> if (local_err != NULL) {
> goto fail_options;
> }
> - if (!bdrv_has_zero_init(bs->file->bs) ||
> +
> + if (!(flags & BDRV_O_RESIZE) || !bdrv_has_zero_init(bs->file->bs) ||
> bdrv_truncate(bs->file, bdrv_getlength(bs->file->bs)) != 0) {
> s->prealloc_mode = PRL_PREALLOC_MODE_FALLOCATE;
> }
Relying on BDRV_O_RESIZE in block drivers is wrong. It is set in some
paths (specifically the users of blk_new_open), but not in others. We
should probably have filtered out the flag before passing it to the
drivers.
As a concrete example, if you're using -blockdev, the bdrv_truncate()
call won't be executed after applying this patch.
I think the correct way would be to check bdrv_is_read_only() instead.
Kevin
