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From: Dave Chinner <david@fromorbit.com>
To: David Howells <dhowells@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	linux-afs@vger.kernel.org,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [GIT PULL] afs: Fixes
Date: Sun, 26 Nov 2017 09:48:06 +1100	[thread overview]
Message-ID: <20171125224806.GM4094@dastard> (raw)
In-Reply-To: <23134.1511649343@warthog.procyon.org.uk>

On Sat, Nov 25, 2017 at 10:35:43PM +0000, David Howells wrote:
> Linus Torvalds <torvalds@linux-foundation.org> wrote:
> 
> > So I see in the commit message why afs needs to do this, but it's
> > worth pointing out that it's
> > 
> >  (a) impossible to avoid the "inconsistent data" case for writable mmap'ed
> >  pages
> 
> Doesn't clear_page_dirty_for_io() write-protect the PTE for the page to be
> written out, in which case ->page_mkwrite() will get called again before the
> page is redirtied?

Yes, but page_mkwrite will only block on writeback in progress is if
the backing device says it needs stable pages.  See
wait_for_stable_page().  e.g. stable pages are required if RAID is
in use, otherwise modification during IO can result in broken
on-disk parity/mirroring....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  reply	other threads:[~2017-11-25 22:48 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-24 14:22 [GIT PULL] afs: Fixes David Howells
2017-11-25 18:05 ` Linus Torvalds
2017-11-25 22:35 ` David Howells
2017-11-25 22:48   ` Dave Chinner [this message]
2017-11-25 22:55   ` Linus Torvalds
2017-11-25 23:19   ` David Howells
  -- strict thread matches above, loose matches on Subject: below --
2020-10-29 14:07 [GIT PULL] afs fixes David Howells
2020-10-29 17:31 ` pr-tracker-bot
2020-04-13 14:50 [GIT PULL] afs: Fixes David Howells
2020-04-13 15:13 ` David Howells
2020-04-14 19:05 ` pr-tracker-bot
2019-08-14 14:18 David Howells
2019-08-14 22:35 ` pr-tracker-bot
2019-08-14 14:15 David Howells
2019-06-26 13:39 [GIT PULL] AFS fixes David Howells
2019-06-28  0:45 ` pr-tracker-bot
2019-06-26  8:50 David Howells
2019-06-26 13:38 ` David Howells
2018-05-14 21:25 [GIT PULL] afs: Fixes David Howells
2017-03-17 15:29 [GIT PULL] AFS fixes David Howells
2017-03-17 19:23 ` Linus Torvalds

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