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From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: "Jeff Layton" <jlayton@redhat.com>, 焦晓冬 <milestonejxd@gmail.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Rogier Wolff" <R.E.Wolff@BitWizard.nl>
Subject: Re: POSIX violation by writeback error
Date: Wed, 26 Sep 2018 17:49:09 -0400	[thread overview]
Message-ID: <20180926214909.GD3688@thunk.org> (raw)
In-Reply-To: <20180926191055.6fc1514f@alans-desktop>

On Wed, Sep 26, 2018 at 07:10:55PM +0100, Alan Cox wrote:
> In almost all cases you don't care so you wouldn't use it. In those cases
> where it might matter it's almost always the case that a reader won't
> consume it before it hits the media.
> 
> That's why I suggested having an fbarrier() so you can explicitly say 'in
> the even that case does happen then stall and write it'. It's kind of
> lazy fsync. That can be used with almost no cost by things like mail
> daemons.

How could mail daemons use it?  They *have* to do an fsync() before
they send a 2xx SMTP return code.

There are plenty of other dependencies besides read --- for example,
if you write a mp3 file, and then write the playlist.m3u file, maybe
the barrier requirement is "if playlist.m3u survives after the crash,
all of the mp3 files mentioned in it must completely written out to
disk".  So I'm not sure how useful a fbarrier(2) would be in practice.

> Another way given that this only really makes sense with locks
> is to add that fbarrier notion as a file locking optional semantic so you
> can 'unlock with barrier' and 'lock with barrier honoured'

I'm not sure what you're suggesting?

						- Ted

  reply	other threads:[~2018-09-27  4:04 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAJDTihx2yaR-_-9Ks1PoFcrKNZgUOoLdN-wRTTMV76Jg_dCLrw@mail.gmail.com>
2018-09-04 10:56 ` POSIX violation by writeback error Jeff Layton
2018-09-24 23:30   ` Alan Cox
2018-09-25 11:15     ` Jeff Layton
2018-09-25 15:46       ` Theodore Y. Ts'o
2018-09-25 16:17         ` Rogier Wolff
2018-09-25 16:39         ` Alan Cox
2018-09-25 16:41         ` Jeff Layton
2018-09-25 22:30           ` Theodore Y. Ts'o
2018-09-26 18:10             ` Alan Cox
2018-09-26 21:49               ` Theodore Y. Ts'o [this message]
2018-09-27 22:48                 ` Alan Cox
2018-09-27  7:18               ` Rogier Wolff
2018-09-27 12:43             ` Jeff Layton
2018-09-27 14:27               ` Theodore Y. Ts'o
2018-09-25 17:35         ` Adam Borowski
2018-09-25 22:46           ` Theodore Y. Ts'o
2018-09-04  6:32 焦晓冬
2018-09-04  7:53 ` Rogier Wolff
2018-09-04  8:58   ` 焦晓冬
2018-09-04  9:29     ` Rogier Wolff
2018-09-04 10:45       ` 焦晓冬
2018-09-04 11:09     ` Jeff Layton
2018-09-04 14:56       ` 焦晓冬
2018-09-04 15:44         ` Jeff Layton
2018-09-04 16:12           ` J. Bruce Fields
2018-09-04 16:23             ` Rogier Wolff
2018-09-04 18:54               ` J. Bruce Fields
2018-09-04 20:18                 ` Jeff Layton
2018-09-04 20:35                   ` Vito Caputo
2018-09-04 21:02                     ` Matthew Wilcox
2018-09-05  0:51                     ` Dave Chinner
2018-09-05  8:24                   ` 焦晓冬
2018-09-05 10:55                     ` Jeff Layton
2018-09-05 12:07                       ` Rogier Wolff
2018-09-06  2:57                         ` Dave Chinner
2018-09-06  9:17                           ` Rogier Wolff
2018-09-24 23:09                             ` Alan Cox
2018-09-05 13:53                       ` J. Bruce Fields
2018-09-05  7:08           ` Rogier Wolff
2018-09-05  7:39             ` Martin Steigerwald
2018-09-05  8:04               ` Rogier Wolff
2018-09-05  8:37                 ` 焦晓冬
2018-09-05 12:07                   ` Austin S. Hemmelgarn
2018-09-05 12:46                     ` Rogier Wolff
2018-09-05  9:32                 ` Martin Steigerwald
2018-09-05  7:37           ` Martin Steigerwald
2018-09-05 11:42             ` Jeff Layton
2018-09-05  8:09           ` 焦晓冬
2018-09-05 13:08             ` Theodore Y. Ts'o
2018-09-24 23:21               ` Alan Cox
2018-09-06  7:28             ` 焦晓冬

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