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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>, Steve French <sfrench@samba.org>,
	Sage Weil <sage@inktank.com>, Mark Fasheh <mfasheh@suse.com>,
	xfs@oss.sgi.com, Christoph Hellwig <hch@infradead.org>,
	Joel Becker <jlbec@evilplan.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	David Miller <davem@davemloft.net>
Subject: Re: [PATCH 0/5] splice: locking changes and code refactoring
Date: Sat, 18 Jan 2014 08:27:30 +0000	[thread overview]
Message-ID: <20140118082730.GH10323@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20140118074649.GF10323@ZenIV.linux.org.uk>

On Sat, Jan 18, 2014 at 07:46:49AM +0000, Al Viro wrote:
> On Fri, Jan 17, 2014 at 11:22:04PM -0800, Linus Torvalds wrote:
> > On Fri, Jan 17, 2014 at 10:40 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> > >
> > > Objections, comments?
> > 
> > I certainly object to the "map, then unmap" approach. No VM games.
[snip]
> > But if it can be done more naturally as a writev, then that may well
> > be ok. As long as we're talking about just the
> > default_file_splice_write() case, and people who want to do special
> > things with page movement can continue to do so..
> 
> The thing is, after such change default_file_splice_write() is no worse than
> generic_file_splice_write().  The only instances that really want something
> else are the ones that try to steal pages (e.g. virtio_console, fuse miscdev)
> or sockets, with their "do DMA from the sodding page, don't copy it at
> anywhere" ->sendpage() method.  IOW, ones those special things you are
> talking about.  Normal filesystems do not - not on pipe-to-file splice.
> file-to-pipe - sure, that one plays with pagecache and tries hard to
> do zero-copy, but that's ->splice_read(), not ->splice_write()...

BTW, would sockets benefit from having ->sendpages() that would take an
array of (page, offset, len) triples?  It would be trivial to do and
some of the helpers that are falling out of writing that writev-based
default_file_splice_write() look like they could be reused for
calling that one...  Dave?

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  parent reply	other threads:[~2014-01-18  8:27 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-12-12 18:14 [PATCH 0/5] splice: locking changes and code refactoring Christoph Hellwig
2013-12-12 18:14 ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 1/5] splice: move balance_dirty_pages_ratelimited into pipe_to_file Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 2/5] splice: nest i_mutex outside pipe_lock Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 3/5] splice: use splice_from_pipe in generic_file_splice_write Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 4/5] xfs: fix splice_write locking Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2013-12-12 18:15 ` [PATCH 5/5] splice: stop exporting splice_from_pipe implementation details Christoph Hellwig
2013-12-12 18:15   ` Christoph Hellwig
2014-01-13 14:14 ` [PATCH 0/5] splice: locking changes and code refactoring Christoph Hellwig
2014-01-13 14:14   ` Christoph Hellwig
2014-01-13 23:56   ` Al Viro
2014-01-13 23:56     ` Al Viro
2014-01-14 13:22     ` Christoph Hellwig
2014-01-14 13:22       ` Christoph Hellwig
2014-01-14 17:20       ` Al Viro
2014-01-14 17:20         ` Al Viro
2014-01-15 18:10         ` Al Viro
2014-01-15 18:10           ` Al Viro
2014-01-18  6:40         ` Al Viro
2014-01-18  7:22           ` Linus Torvalds
2014-01-18  7:22             ` Linus Torvalds
2014-01-18  7:46             ` Al Viro
2014-01-18  7:56               ` Al Viro
2014-01-18  7:56                 ` Al Viro
2014-01-18  8:27               ` Al Viro [this message]
2014-01-18  8:44                 ` David Miller
2014-01-18  8:44                   ` David Miller
2014-02-07 17:10                   ` Al Viro
2014-02-07 17:10                     ` Al Viro
2014-01-18 19:59               ` Linus Torvalds
2014-01-18 20:10                 ` Al Viro
2014-01-18 20:27                   ` Al Viro
2014-01-18 20:27                     ` Al Viro
2014-01-18 20:30                     ` Al Viro
2014-01-18 20:30                       ` Al Viro
2014-01-19  5:13                   ` [RFC] unifying write variants for filesystems Al Viro
2014-01-19  5:13                     ` Al Viro
2014-01-20 13:55                     ` Christoph Hellwig
2014-01-20 13:55                       ` Christoph Hellwig
2014-01-20 20:32                       ` Linus Torvalds
2014-01-20 20:32                         ` Linus Torvalds
2014-02-01 22:43                         ` Al Viro
2014-02-01 22:43                           ` Al Viro
2014-02-02  0:13                           ` Linus Torvalds
2014-02-02  2:02                             ` Al Viro
2014-02-02  2:02                               ` Al Viro
2014-02-02 19:21                           ` Al Viro
2014-02-02 19:21                             ` Al Viro
2014-02-02 19:23                             ` Al Viro
2014-02-02 19:23                               ` Al Viro
2014-02-03 14:41                             ` Miklos Szeredi
2014-02-03 14:41                               ` Miklos Szeredi
2014-02-03 15:33                               ` Al Viro
2014-02-03 15:33                                 ` Al Viro
2014-02-02 23:16                           ` Anton Altaparmakov
2014-02-02 23:16                             ` Anton Altaparmakov
2014-02-03 15:12                           ` Christoph Hellwig
2014-02-03 16:24                             ` Al Viro
2014-02-03 16:50                             ` Dave Kleikamp
2014-02-03 16:23                           ` Dave Kleikamp
2014-02-04 12:44                             ` Al Viro
2014-02-04 12:44                               ` Al Viro
2014-02-04 12:52                               ` Kent Overstreet
2014-02-04 12:52                                 ` Kent Overstreet
2014-02-04 15:17                                 ` Al Viro
2014-02-04 15:17                                   ` Al Viro
2014-02-04 17:27                                   ` Zach Brown
2014-02-04 17:35                                     ` Kent Overstreet
2014-02-04 18:08                                       ` Al Viro
2014-02-04 18:08                                         ` Al Viro
2014-02-04 18:00                                     ` Al Viro
2014-02-04 18:00                                       ` Al Viro
2014-02-04 18:33                                       ` Zach Brown
2014-02-04 18:36                                         ` Al Viro
2014-02-04 18:36                                           ` Al Viro
2014-02-05 19:58                                           ` Al Viro
2014-02-05 20:42                                             ` Zach Brown
2014-02-06  9:08                                             ` Kent Overstreet

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