[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH 6/9] ssh: Support BDRV_REQ_ZERO_WRITE for truncate
From: |
Richard W.M. Jones |
Subject: |
Re: [PATCH 6/9] ssh: Support BDRV_REQ_ZERO_WRITE for truncate |
Date: |
Wed, 29 Apr 2020 10:01:12 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Apr 28, 2020 at 03:29:02PM -0500, Eric Blake wrote:
> Our .bdrv_has_zero_init_truncate can detect when the remote side
> always zero fills; we can reuse that same knowledge to implement
> BDRV_REQ_ZERO_WRITE by ignoring it when the server gives it to us for
> free.
>
> Signed-off-by: Eric Blake <address@hidden>
> ---
> block/ssh.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/block/ssh.c b/block/ssh.c
> index 9eb33df8598c..f9e08a490069 100644
> --- a/block/ssh.c
> +++ b/block/ssh.c
> @@ -883,6 +883,10 @@ static int ssh_file_open(BlockDriverState *bs, QDict
> *options, int bdrv_flags,
> /* Go non-blocking. */
> ssh_set_blocking(s->session, 0);
>
> + if (s->attrs->type == SSH_FILEXFER_TYPE_REGULAR) {
> + bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
> + }
> +
As the libssh sftp API is written this is all fine, so ACK:
Reviewed-by: Richard W.M. Jones <address@hidden>
On the other hand the actual openssh / libssh code is a bit hairy.
Openssh simply copies the st_mode field onto the wire (with
byte-swapping). Libssh assumes that S_IFREG == 0100000 and translates
this bit to SSH_FILEXFER_TYPE_REGULAR. This happens to be true on
Linux and *BSD but as far as I can tell isn't defined in POSIX.
Anyway I guess it'll work in all places that we care about.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines. Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top
- [PATCH 0/9] More truncate improvements, Eric Blake, 2020/04/28
- [PATCH 2/9] file-win32: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- [PATCH 3/9] nfs: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- [PATCH 1/9] gluster: Drop useless has_zero_init callback, Eric Blake, 2020/04/28
- [PATCH 4/9] rbd: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- [PATCH 6/9] ssh: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- Re: [PATCH 6/9] ssh: Support BDRV_REQ_ZERO_WRITE for truncate,
Richard W.M. Jones <=
- [PATCH 5/9] sheepdog: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- [PATCH 7/9] parallels: Rework truncation logic, Eric Blake, 2020/04/28
- [PATCH 8/9] vhdx: Rework truncation logic, Eric Blake, 2020/04/28
- [PATCH 9/9] block: Drop unused .bdrv_has_zero_init_truncate, Eric Blake, 2020/04/28
- Re: [PATCH 0/9] More truncate improvements, no-reply, 2020/04/28
- Re: [PATCH 0/9] More truncate improvements, no-reply, 2020/04/28