From: Jesse Pollard <jesse@cats-chateau.net>
To: David Woodhouse <dwmw2@infradead.org>
Cc: "Ihar 'Philips' Filipau" <filia@softhome.net>,
Davide Rossetti <davide.rossetti@roma1.infn.it>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: OT: why no file copy() libc/syscall ??
Date: Mon, 10 Nov 2003 10:15:34 -0600 [thread overview]
Message-ID: <03111010153401.08768@tabby> (raw)
In-Reply-To: <1068477550.5743.50.camel@hades.cambridge.redhat.com>
On Monday 10 November 2003 09:19, David Woodhouse wrote:
> On Mon, 2003-11-10 at 07:29 -0600, Jesse Pollard wrote:
> > > > sys_fscopy(...)
> >
> > It is too simple to implement in user mode.
>
> Is it? Please explain the simple steps which cp(1) should take in order
> to observe that it is being asked to duplicate a file on a file system
> such as CIFS (or NFSv4?) which allows the client to issue a 'copy file'
> command over the network without actually transferring the data twice,
> and to invoke such a command.
Ah. That is an optimization question, not a question of kernel/user mode.
Since the error checking for source and destination both include doing
a stat and statfs, the device information (and FS info) can both be retrieved.
And mmap doesn't require data transfer "twice" (local copy). Since that copy
only pagefaults (though read/write may be faster for some files - I thought
that was true for small files that fit in cache, and large files faster via
mmap and depends on the page size; and the tradeoff would be system
dependant).
And since both source and destination may be remote you do get to decide
based on source and destination devices: if they are the same, and one on
a remote node, then BOTH will be on the remote, then you get to use the
CIFS/NFS file copy. (check the doc on "stat/statfs" for additional info).
I don't believe it works when source and destination are on DIFFERENT remote
nodes, though.
Strictly up to the implementation of cp/mv.
Though you will loose portability of cp/mv. (Of course, you also loose
it with a syscall for file copy too; as well as the MUCH more complicated
implementation/security checks).
next prev parent reply other threads:[~2003-11-10 16:16 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <QiyV.1k3.15@gated-at.bofh.it>
2003-11-10 12:08 ` OT: why no file copy() libc/syscall ?? Ihar 'Philips' Filipau
2003-11-10 13:29 ` Jesse Pollard
2003-11-10 14:22 ` Daniel Jacobowitz
2003-11-11 20:57 ` Jakob Oestergaard
2003-11-10 15:19 ` David Woodhouse
2003-11-10 16:15 ` Jesse Pollard [this message]
2003-11-11 12:00 ` davide.rossetti
2003-11-11 12:08 ` Andreas Schwab
2003-11-11 12:23 ` davide.rossetti
[not found] <1068512710.722.161.camel@cube.suse.lists.linux.kernel>
[not found] ` <20031111133859.GA11115@bitwizard.nl.suse.lists.linux.kernel>
[not found] ` <20031111085323.M8854@devserv.devel.redhat.com.suse.lists.linux.kernel>
[not found] ` <bp0p5m$lke$1@cesium.transmeta.com.suse.lists.linux.kernel>
[not found] ` <20031113233915.GO1649@x30.random.suse.lists.linux.kernel>
[not found] ` <3FB4238A.40605@zytor.com.suse.lists.linux.kernel>
[not found] ` <20031114011009.GP1649@x30.random.suse.lists.linux.kernel>
[not found] ` <3FB42CC4.9030009@zytor.com.suse.lists.linux.kernel>
2003-11-14 15:26 ` Andi Kleen
2003-11-18 15:49 ` Jamie Lokier
2003-11-18 16:05 ` Andi Kleen
2003-11-18 16:25 ` Trond Myklebust
2003-11-19 13:30 ` Jesse Pollard
2003-11-18 16:58 ` H. Peter Anvin
2003-11-19 2:12 ` Linus Torvalds
2003-11-19 4:04 ` Chris Adams
[not found] <Qvw7.5Qf.9@gated-at.bofh.it>
[not found] ` <QxRl.17Y.9@gated-at.bofh.it>
[not found] ` <Qy0W.1sk.9@gated-at.bofh.it>
[not found] ` <QyaB.1GK.17@gated-at.bofh.it>
[not found] ` <QzSZ.4x1.1@gated-at.bofh.it>
[not found] ` <QCHh.X6.3@gated-at.bofh.it>
2003-11-11 9:51 ` Ihar 'Philips' Filipau
2003-11-11 10:41 ` jw schultz
[not found] ` <QH4e.eV.3@gated-at.bofh.it>
2003-11-11 14:11 ` Ihar 'Philips' Filipau
2003-11-11 15:02 ` Rogier Wolff
2003-11-11 15:31 ` Ihar 'Philips' Filipau
2003-11-11 20:22 ` Jan Harkes
2003-11-11 20:31 ` Valdis.Kletnieks
[not found] <QDtX.2dq.15@gated-at.bofh.it>
[not found] ` <QDtX.2dq.17@gated-at.bofh.it>
[not found] ` <QDtX.2dq.19@gated-at.bofh.it>
[not found] ` <QDtX.2dq.21@gated-at.bofh.it>
[not found] ` <QDtX.2dq.23@gated-at.bofh.it>
[not found] ` <QDtY.2dq.25@gated-at.bofh.it>
[not found] ` <QDtX.2dq.13@gated-at.bofh.it>
[not found] ` <QEg2.3zi.9@gated-at.bofh.it>
2003-11-11 12:43 ` Ihar 'Philips' Filipau
2003-11-11 1:05 Albert Cahalan
2003-11-11 3:50 ` Andreas Dilger
2003-11-11 4:03 ` Daniel Gryniewicz
2003-11-11 4:14 ` Valdis.Kletnieks
2003-11-11 6:00 ` Andreas Dilger
2003-11-11 8:58 ` Florian Weimer
2003-11-11 10:27 ` jw schultz
2003-11-11 20:08 ` Jan Harkes
2003-11-12 15:36 ` Jesse Pollard
2003-11-20 17:21 ` Florian Weimer
2003-11-20 19:08 ` Jesse Pollard
2003-11-20 19:12 ` Florian Weimer
2003-11-20 19:44 ` Justin Cormack
2003-11-20 20:44 ` Timothy Miller
2003-11-20 21:07 ` Andreas Dilger
2003-11-20 21:30 ` Timothy Miller
2003-11-20 21:49 ` Maciej Zenczykowski
2003-11-20 21:52 ` Timothy Miller
2003-11-20 21:58 ` Hua Zhong
2003-11-22 14:50 ` Pavel Machek
2003-11-22 19:50 ` Jamie Lokier
2003-11-22 23:07 ` Andreas Schwab
2003-11-21 16:24 ` Jesse Pollard
2003-11-20 21:48 ` Maciej Zenczykowski
2003-11-21 16:34 ` Jesse Pollard
2003-11-20 22:31 ` Xavier Bestel
2003-11-20 22:44 ` Andreas Dilger
2003-11-27 2:40 ` Robert White
2003-11-27 7:29 ` Nick Piggin
2003-11-27 9:15 ` David Lang
2003-11-27 8:56 ` Nick Piggin
2003-11-27 9:50 ` David Lang
2003-11-27 10:02 ` Jörn Engel
2003-11-27 10:58 ` David Lang
2003-12-01 16:20 ` Jesse Pollard
2003-11-11 8:52 ` Gábor Lénárt
2003-11-11 13:38 ` Rogier Wolff
2003-11-11 13:53 ` Jakub Jelinek
2003-11-11 13:58 ` David Woodhouse
2003-11-13 20:22 ` H. Peter Anvin
2003-11-13 23:39 ` Andrea Arcangeli
2003-11-14 0:04 ` jw schultz
2003-11-14 0:36 ` H. Peter Anvin
2003-11-14 1:10 ` Andrea Arcangeli
2003-11-14 1:15 ` H. Peter Anvin
2003-11-11 14:11 ` Albert Cahalan
2003-11-12 15:19 ` Jesse Pollard
2003-11-14 3:42 ` Albert Cahalan
-- strict thread matches above, loose matches on Subject: below --
2003-11-10 12:09 Bradley Chapman
2003-11-10 18:47 ` Tomas Konir
2003-11-10 22:44 ` Derek Foreman
2003-11-10 11:33 Davide Rossetti
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