From: Andrew Morton <akpm@digeo.com>
To: paulmck@us.ibm.com
Cc: andrea@suse.de, dmccr@us.ibm.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Fix vmtruncate race and distributed filesystem race
Date: Sun, 22 Jun 2003 23:32:35 -0700 [thread overview]
Message-ID: <20030622233235.0924364d.akpm@digeo.com> (raw)
In-Reply-To: <20030623032842.GA1167@us.ibm.com>
"Paul E. McKenney" <paulmck@us.ibm.com> wrote:
>
> > but you can't trap this with a single counter increment in do_truncate:
> >
> > CPU 0 CPU 1
> > ---------- -----------
> > do_no_page
> > truncate
i_size = new_i_size;
> > increment counter
> > read counter
> > ->nopage
check i_size
> > vmtruncate
> > read counter again -> different so retry
> >
> > thanks to the second counter increment after vmtruncate in my fix, the
> > above race couldn't happen.
>
> The trick is that CPU 0 is expected to have updated the filesystem's
> idea of what pages are available before calling vmtruncate,
> invalidate_mmap_range() or whichever.
i_size has been updated, and filemap_nopage() will return NULL.
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@digeo.com>
To: paulmck@us.ibm.com
Cc: andrea@suse.de, dmccr@us.ibm.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Fix vmtruncate race and distributed filesystem race
Date: Sun, 22 Jun 2003 23:32:35 -0700 [thread overview]
Message-ID: <20030622233235.0924364d.akpm@digeo.com> (raw)
In-Reply-To: <20030623032842.GA1167@us.ibm.com>
"Paul E. McKenney" <paulmck@us.ibm.com> wrote:
>
> > but you can't trap this with a single counter increment in do_truncate:
> >
> > CPU 0 CPU 1
> > ---------- -----------
> > do_no_page
> > truncate
i_size = new_i_size;
> > increment counter
> > read counter
> > ->nopage
check i_size
> > vmtruncate
> > read counter again -> different so retry
> >
> > thanks to the second counter increment after vmtruncate in my fix, the
> > above race couldn't happen.
>
> The trick is that CPU 0 is expected to have updated the filesystem's
> idea of what pages are available before calling vmtruncate,
> invalidate_mmap_range() or whichever.
i_size has been updated, and filemap_nopage() will return NULL.
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next prev parent reply other threads:[~2003-06-23 6:18 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-06-12 20:16 [PATCH] Fix vmtruncate race and distributed filesystem race Dave McCracken
2003-06-12 20:49 ` Andrew Morton
2003-06-12 20:49 ` Andrew Morton
2003-06-12 21:00 ` Andrew Morton
2003-06-12 21:00 ` Andrew Morton
2003-06-12 21:08 ` Dave McCracken
2003-06-12 21:08 ` Dave McCracken
2003-06-12 21:44 ` Andrew Morton
2003-06-12 21:44 ` Andrew Morton
2003-06-12 22:56 ` Dave McCracken
2003-06-12 23:07 ` Andrew Morton
2003-06-12 23:07 ` Andrew Morton
2003-06-20 0:17 ` Andrea Arcangeli
2003-06-20 0:17 ` Andrea Arcangeli
2003-06-23 3:28 ` Paul E. McKenney
2003-06-23 3:28 ` Paul E. McKenney
2003-06-23 6:29 ` Andrea Arcangeli
2003-06-23 6:29 ` Andrea Arcangeli
2003-06-23 6:32 ` Andrew Morton [this message]
2003-06-23 6:32 ` Andrew Morton
2003-06-23 7:43 ` Andrea Arcangeli
2003-06-23 7:43 ` Andrea Arcangeli
2003-06-23 7:56 ` Andrew Morton
2003-06-23 7:56 ` Andrew Morton
2003-06-23 8:10 ` Andrea Arcangeli
2003-06-23 8:10 ` Andrea Arcangeli
2003-06-24 1:37 ` Paul E. McKenney
2003-06-24 1:37 ` Paul E. McKenney
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