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From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: Jeff Layton <jlayton@redhat.com>
Cc: "Alan Cox" <gnomes@lxorguk.ukuu.org.uk>,
	焦晓冬 <milestonejxd@gmail.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Rogier Wolff" <R.E.Wolff@BitWizard.nl>,
	"Matthew Wilcox" <willy@infradead.org>
Subject: Re: POSIX violation by writeback error
Date: Thu, 27 Sep 2018 10:27:38 -0400	[thread overview]
Message-ID: <20180927142738.GA27040@thunk.org> (raw)
In-Reply-To: <51b401b82356c2d8e124bb8701f310afd98e0838.camel@redhat.com>

On Thu, Sep 27, 2018 at 08:43:10AM -0400, Jeff Layton wrote:
> 
> Basically, the problem (as I see it) is that we can end up evicting
> uncleanable data from the cache before you have a chance to call fsync,
> and that means that the results of a read after a write are not
> completely reliable.

Part of the problem is that people don't agree on what the problem is.  :-)

The original posting was from someone who claimed it was a "POSIX
violation" if a subsequent read returns *successfully*, but then the
writeback succeeds.

Other people are worried about this problem; yet others are worried
about the system wedging and OOM-killing itself, etc.

The problem is that in the face of I/O errors, it's impossible to keep
everyone happy.  (You could make the local storage device completely
reliable, with a multi-million dollar storage array with remote
replication, but then the CFO won't be happy; and other people were
talking about making things work with cheap USB thumb drives and
laptops.  This is the very definition of an over-constained problem.)

       	      	   	      	    		    - Ted

  reply	other threads:[~2018-09-27 14:27 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
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 [this message]
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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