Commit ecdbead6 authored by Eric Blake's avatar Eric Blake Committed by Kevin Wolf
Browse files

qcow2: Inform block layer about discard boundaries 



At the qcow2 layer, discard is only possible on a per-cluster
basis; at the moment, qcow2 silently rounds any unaligned
requests to this granularity.  However, an upcoming patch will
fix a regression in the block layer ignoring too much of an
unaligned discard request, by changing the block layer to
break up a discard request at alignment boundaries; for that
to work, the block layer must know about our limits.

However, we can't go one step further by changing
qcow2_discard_clusters() to assert that requests are always
aligned, since that helper function is reached on paths
outside of the block layer.

CC: qemu-stable@nongnu.org
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent a7764f15

block/qcow2.c

+1 −0
Original line number Diff line number Diff line
@@ -1206,6 +1206,7 @@ static void qcow2_refresh_limits(BlockDriverState *bs, Error **errp) 
        bs->bl.request_alignment = BDRV_SECTOR_SIZE;

    }

    bs->bl.pwrite_zeroes_alignment = s->cluster_size;

    bs->bl.pdiscard_alignment = s->cluster_size;

}



static int qcow2_set_key(BlockDriverState *bs, const char *key)