From: "Myklebust, Trond" <Trond.Myklebust@netapp.com>
To: Zach Brown <zab@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Ric Wheeler <rwheeler@redhat.com>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Chris L. Mason" <clmason@fusionio.com>,
Christoph Hellwig <hch@infradead.org>,
Alexander Viro <aviro@redhat.com>,
"Martin K. Petersen" <mkp@mkp.net>,
"Hannes Reinecke" <hare@suse.de>,
Joel Becker <jlbec@evilplan.org>
Subject: RE: New copyfile system call - discuss before LSF?
Date: Fri, 22 Feb 2013 01:29:56 +0000 [thread overview]
Message-ID: <4FA345DA4F4AE44899BD2B03EEEC2FA9235DB089@SACEXCMBX04-PRD.hq.netapp.com> (raw)
In-Reply-To: <20130221222449.GY22221@lenny.home.zabbo.net>
> -----Original Message-----
> From: Zach Brown [mailto:zab@redhat.com]
> Sent: Thursday, February 21, 2013 5:25 PM
> To: Myklebust, Trond
> Cc: Paolo Bonzini; Ric Wheeler; Linux FS Devel; linux-kernel@vger.kernel.org;
> Chris L. Mason; Christoph Hellwig; Alexander Viro; Martin K. Petersen;
> Hannes Reinecke; Joel Becker
> Subject: Re: New copyfile system call - discuss before LSF?
>
> On Thu, Feb 21, 2013 at 08:50:27PM +0000, Myklebust, Trond wrote:
> > On Thu, 2013-02-21 at 21:00 +0100, Paolo Bonzini wrote:
> > > Il 21/02/2013 15:57, Ric Wheeler ha scritto:
> > > >>>
> > > >> sendfile64() pretty much already has the right arguments for a
> > > >> "copyfile", however it would be nice to add a 'flags' parameter:
> > > >> the
> > > >> NFSv4.2 version would use that to specify whether or not to copy
> > > >> file metadata.
> > > >
> > > > That would seem to be enough to me and has the advantage that it
> > > > is an relatively obvious extension to something that is at least
> > > > not totally unknown to developers.
> > > >
> > > > Do we need more than that for non-NFS paths I wonder? What does
> > > > reflink need or the SCSI mechanism?
> > >
> > > For virt we would like to be able to specify arbitrary block ranges.
> > > Copying an entire file helps some copy operations like storage
> > > migration. However, it is not enough to convert the guest's
> > > offloaded copies to host-side offloaded copies.
> >
> > So how would a system call based on sendfile64() plus my flag
> > parameter prevent an underlying implementation from meeting your
> criterion?
>
> If I'm guessing correctly, sendfile64()+flags would be annoying because it's
> missing an out_fd_offset. The host will want to offload the guest's copies by
> calling sendfile on block ranges of a guest disk image file that correspond to
> the mappings of the in and out files in the guest.
>
> You could make it work with some locking and out_fd seeking to set the
> write offset before calling sendfile64()+flags, but ugh.
>
> ssize_t sendfile(int out_fd, int in_fd, off_t in_offset, off_t
> out_offset, size_t count, int flags);
>
> That seems closer.
psendfile() ?
I fully agree that sounds reasonable... Just being an ass. :-)
> We might also want to pre-emptively offer iovs instead of offsets, because
> that's the very first thing that's going to be requested after people prototype
> having to iterate calling sendfile() for each contiguous copy region.
vpsendfile() then? I agree that might be a little more future-proof. Particularly given that the underlying protocols tend to be fully asynchronous, and so it makes sense to queue up more than one copy at a time...
Cheers,
Trond
next prev parent reply other threads:[~2013-02-22 1:30 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-21 11:37 New copyfile system call - discuss before LSF? Ric Wheeler
2013-02-21 13:37 ` Hannes Reinecke
2013-02-21 13:51 ` Myklebust, Trond
2013-02-21 14:57 ` Ric Wheeler
2013-02-21 16:36 ` Andreas Dilger
2013-02-21 20:00 ` Paolo Bonzini
2013-02-21 20:50 ` Myklebust, Trond
2013-02-21 22:24 ` Zach Brown
2013-02-22 1:29 ` Myklebust, Trond [this message]
2013-02-23 0:32 ` Eric Wong
2013-03-30 19:45 ` Pavel Machek
2013-03-31 21:23 ` Eric Wong
2013-02-22 9:47 ` Paolo Bonzini
2013-02-22 9:52 ` Ric Wheeler
2013-02-22 18:22 ` Zach Brown
2013-02-22 22:48 ` Myklebust, Trond
2013-02-25 21:14 ` Andy Lutomirski
2013-02-25 21:49 ` Ric Wheeler
2013-02-25 21:59 ` Myklebust, Trond
2013-02-25 22:16 ` Andy Lutomirski
2013-02-25 23:28 ` Myklebust, Trond
2013-02-25 23:35 ` Andy Lutomirski
2013-02-25 23:45 ` Myklebust, Trond
2013-02-26 0:03 ` Zach Brown
2013-03-11 9:31 ` Joel Becker
2013-02-26 21:02 ` Jörn Engel
2013-02-26 22:35 ` Andy Lutomirski
2013-03-30 19:49 ` Pavel Machek
2013-03-30 20:08 ` Andreas Dilger
2013-03-30 21:45 ` Pavel Machek
2013-03-30 21:57 ` Myklebust, Trond
2013-03-30 23:21 ` Ric Wheeler
2013-03-31 2:53 ` Andreas Dilger
2013-03-31 3:52 ` Myklebust, Trond
2013-03-31 4:18 ` Andy Lutomirski
2013-03-31 4:36 ` Myklebust, Trond
2013-03-31 4:45 ` Myklebust, Trond
2013-04-01 15:49 ` J. Bruce Fields
2013-03-31 7:36 ` Pavel Machek
2013-03-31 18:27 ` Myklebust, Trond
2013-03-31 18:32 ` openat(..., AT_UNLINKED) was " Pavel Machek
2013-03-31 18:44 ` Myklebust, Trond
2013-03-31 22:50 ` Pavel Machek
2013-03-31 23:14 ` Ric Wheeler
2013-03-31 23:18 ` Pavel Machek
2013-03-31 23:28 ` Ric Wheeler
2013-03-31 23:41 ` Pavel Machek
2013-03-31 5:38 ` AEDilger Gmail
2013-03-31 8:25 ` Pavel Machek
2013-03-31 11:48 ` Pádraig Brady
2013-03-30 22:40 ` Andy Lutomirski
2013-02-21 22:05 ` Ric Wheeler
2013-02-21 22:13 ` Myklebust, Trond
2013-02-22 8:47 ` Ric Wheeler
2013-02-21 18:29 ` Jeremy Allison
2013-02-22 0:29 ` Eric Wong
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4FA345DA4F4AE44899BD2B03EEEC2FA9235DB089@SACEXCMBX04-PRD.hq.netapp.com \
--to=trond.myklebust@netapp.com \
--cc=aviro@redhat.com \
--cc=clmason@fusionio.com \
--cc=hare@suse.de \
--cc=hch@infradead.org \
--cc=jlbec@evilplan.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mkp@mkp.net \
--cc=pbonzini@redhat.com \
--cc=rwheeler@redhat.com \
--cc=zab@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).