From: Eric Blake <eblake@redhat.com>
Date: Tue, 28 Apr 2020 20:29:00 +0000 (-0500)
Subject: rbd: Support BDRV_REQ_ZERO_WRITE for truncate
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=2f98910d5b89733b1a5df06c6d2a7056da32a7b7;p=qemu.git

rbd: Support BDRV_REQ_ZERO_WRITE for truncate

Our .bdrv_has_zero_init_truncate always returns 1 because rbd always
0-fills; we can use that same knowledge to implement
BDRV_REQ_ZERO_WRITE by ignoring it.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200428202905.770727-5-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---

diff --git a/block/rbd.c b/block/rbd.c
index f2d52091c7..331c45adb2 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -817,6 +817,9 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
         }
     }
 
+    /* When extending regular files, we get zeros from the OS */
+    bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
+
     r = 0;
     goto out;