From 8f23aaf5d6a5458e251c5d5d0555d9e515355e35 Mon Sep 17 00:00:00 2001
From: Eric Blake <eblake@redhat.com>
Date: Tue, 28 Apr 2020 15:28:59 -0500
Subject: [PATCH] nfs: Support BDRV_REQ_ZERO_WRITE for truncate
Our .bdrv_has_zero_init_truncate returns 1 if we detect that the OS
always 0-fills; we can use that same knowledge to implement
BDRV_REQ_ZERO_WRITE by ignoring it when the OS gives it to us for
free.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200428202905.770727-4-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block/nfs.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/block/nfs.c b/block/nfs.c
index 385d756e1d..76daa7c9f6 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -620,6 +620,9 @@ static int nfs_file_open(BlockDriverState *bs, QDict *options, int flags,
}
bs->total_sectors = ret;
+ if (client->has_zero_init) {
+ bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
+ }
return 0;
}