From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57357) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c9DZE-0002G7-4E for qemu-devel@nongnu.org; Tue, 22 Nov 2016 11:05:13 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c9DZD-0006I5-8l for qemu-devel@nongnu.org; Tue, 22 Nov 2016 11:05:08 -0500 From: Kevin Wolf Date: Tue, 22 Nov 2016 17:04:50 +0100 Message-Id: <1479830693-26676-2-git-send-email-kwolf@redhat.com> In-Reply-To: <1479830693-26676-1-git-send-email-kwolf@redhat.com> References: <1479830693-26676-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PULL 1/4] qcow2: Inform block layer about discard boundaries List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, stefanha@redhat.com, qemu-devel@nongnu.org From: Eric Blake 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 6d5689a..e22f6dc 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) -- 1.8.3.1