On Mon, Aug 17, 2020 at 12:15:43PM +0300, Vladimir Sementsov-Ogievskiy wrote: > The comments states, that on misaligned request we should have already > been waiting. But for bdrv_padding_rmw_read, we called > bdrv_mark_request_serialising with align = request_alignment, and now > we serialise with align = cluster_size. So we may have to wait again > with larger alignment. > > Note, that the only user of BDRV_REQ_SERIALISING is backup which issues > cluster-aligned requests, so seems the assertion should not fire for > now. But it's wrong anyway. > > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com> > --- > block/io.c | 11 +---------- > 1 file changed, 1 insertion(+), 10 deletions(-)
This code was added by Paolo, CCing him.
> diff --git a/block/io.c b/block/io.c
> index ad3a51ed53..b18680a842 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -1881,7 +1881,6 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t
> offset, uint64_t bytes,
> BdrvTrackedRequest *req, int flags)
> {
> BlockDriverState *bs = child->bs;
> - bool waited;
> int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
>
> if (bs->read_only) {
> @@ -1893,15 +1892,7 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t
> offset, uint64_t bytes,
> assert(!(flags & ~BDRV_REQ_MASK));
>
> if (flags & BDRV_REQ_SERIALISING) {
> - waited = bdrv_mark_request_serialising(req,
> bdrv_get_cluster_size(bs));
> - /*
> - * For a misaligned request we should have already waited earlier,
> - * because we come after bdrv_padding_rmw_read which must be called
> - * with the request already marked as serialising.
> - */
> - assert(!waited ||
> - (req->offset == req->overlap_offset &&
> - req->bytes == req->overlap_bytes));
> + bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
> } else {
> bdrv_wait_serialising_requests(req);
> }
> --
> 2.18.0
>
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