From ecdbead659f037dc572bba9eb1cd31a5a1a9ad9a Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Thu, 17 Nov 2016 14:13:55 -0600 Subject: [PATCH] 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: Eric Blake Reviewed-by: Max Reitz Signed-off-by: Kevin Wolf --- block/qcow2.c | 1 + 1 file changed, 1 insertion(+) diff --git a/block/qcow2.c b/block/qcow2.c index 6d5689a23c..e22f6dc0c6 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -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) -- 2.39.2