More truncate improvements

[PATCH 3/9] nfs: Support BDRV_REQ_ZERO_WRITE for truncate

Eric Blake posted 9 patches 5 years, 9 months ago

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Maintainers: Peter Lieven <pl@kamp.de>, "Denis V. Lunev" <den@openvz.org>, Stefan Weil <sw@weilnetz.de>, Jason Dillaman <dillaman@redhat.com>, Max Reitz <mreitz@redhat.com>, Jeff Cody <codyprime@gmail.com>, Kevin Wolf <kwolf@redhat.com>, Liu Yuan <namei.unix@gmail.com>, "Richard W.M. Jones" <rjones@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>

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[PATCH 3/9] nfs: Support BDRV_REQ_ZERO_WRITE for truncate

Posted by Eric Blake 5 years, 9 months ago

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>
---
 block/nfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/nfs.c b/block/nfs.c
index 2393fbfe6bcc..b93989265630 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -623,6 +623,9 @@ 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;
+    }
     ret = 0;
     return ret;
 }
-- 
2.26.2