From: "Richard W.M. Jones" <rjones@redhat.com>
To: Eric Blake <eblake@redhat.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org, qemu-block@nongnu.org,
Max Reitz <mreitz@redhat.com>
Subject: Re: [PATCH 6/9] ssh: Support BDRV_REQ_ZERO_WRITE for truncate
Date: Wed, 29 Apr 2020 10:01:12 +0100 [thread overview]
Message-ID: <20200429090112.GQ3888@redhat.com> (raw)
In-Reply-To: <20200428202905.770727-7-eblake@redhat.com>
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 <eblake@redhat.com>
> ---
> 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 <rjones@redhat.com>
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
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next prev parent reply other threads:[~2020-04-29 9:07 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 20:28 [PATCH 0/9] More truncate improvements Eric Blake
2020-04-28 20:28 ` [PATCH 1/9] gluster: Drop useless has_zero_init callback Eric Blake
2020-04-28 20:28 ` [PATCH 2/9] file-win32: Support BDRV_REQ_ZERO_WRITE for truncate Eric Blake
2020-04-28 20:28 ` [PATCH 3/9] nfs: " Eric Blake
2020-04-28 20:29 ` [PATCH 4/9] rbd: " Eric Blake
2020-04-28 20:29 ` [PATCH 5/9] sheepdog: " Eric Blake
2020-04-28 20:29 ` [PATCH 6/9] ssh: " Eric Blake
2020-04-29 9:01 ` Richard W.M. Jones [this message]
2020-04-28 20:29 ` [PATCH 7/9] parallels: Rework truncation logic Eric Blake
2020-05-07 11:14 ` Denis V. Lunev
2020-04-28 20:29 ` [PATCH 8/9] vhdx: " Eric Blake
2020-04-28 20:29 ` [PATCH 9/9] block: Drop unused .bdrv_has_zero_init_truncate Eric Blake
2020-04-29 9:02 ` Richard W.M. Jones
2020-04-29 2:24 ` [PATCH 0/9] More truncate improvements no-reply
2020-04-29 13:14 ` Eric Blake
2020-04-29 2:24 ` no-reply
2020-05-06 13:03 ` Eric Blake
2020-05-07 10:15 ` Kevin Wolf
2020-05-07 14:29 ` Eric Blake
2020-05-07 14:32 ` Kevin Wolf
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