From: Christoph Hellwig <hch@infradead.org>
To: Theodore Tso <tytso@google.com>
Cc: Michel Lespinasse <walken@google.com>,
Hugh Dickins <hughd@google.com>,
Christoph Hellwig <hch@infradead.org>,
Dave Chinner <david@fromorbit.com>,
Peter Zijlstra <peterz@infradead.org>,
Nick Piggin <npiggin@kernel.dk>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>,
Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Michael Rubin <mrubin@google.com>,
Suleiman Souhlal <suleiman@google.com>
Subject: Re: [PATCH 3/3] mlock: avoid dirtying pages and triggering writeback
Date: Fri, 19 Nov 2010 10:06:41 -0500 [thread overview]
Message-ID: <20101119150641.GA5302@infradead.org> (raw)
In-Reply-To: <AANLkTinzhsvx=fx8dPpnJD_P70HKDRK+tWgFyYEN2_Zm@mail.gmail.com>
On Fri, Nov 19, 2010 at 08:42:05AM -0500, Theodore Tso wrote:
> My vote would be against. ? If you if you mmap a sparse file and then
> try writing to it willy-nilly, bad things will happen. ?This is true without
> a mlock(). ? Where is it written that mlock() has anything to do with
> improving this situation?
Exactly. Allocating space has been a side-effect on a handfull
filesystem for about 20 kernel releases.
> If userspace wants to call fallocate() before it calls mlock(), it should
> do that. ?And in fact, in most cases, userspace should probably be
> encouraged to do that. ? But having mlock() call fallocate() and
> then return ENOSPC if there's no room? Isn't it confusing that mlock()
> call ENOSPC? Doesn't that give you cognitive dissonance? It should
> because fundamentally mlock() has nothing to do with block allocation!!
> Read the API spec!
Indeed. There is no need to make mlock + flag a parallel-API to
fallocate.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Theodore Tso <tytso@google.com>
Cc: Michel Lespinasse <walken@google.com>,
Hugh Dickins <hughd@google.com>,
Christoph Hellwig <hch@infradead.org>,
Dave Chinner <david@fromorbit.com>,
Peter Zijlstra <peterz@infradead.org>,
Nick Piggin <npiggin@kernel.dk>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>,
Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Michael Rubin <mrubin@google.com>,
Suleiman Souhlal <suleiman@google.com>
Subject: Re: [PATCH 3/3] mlock: avoid dirtying pages and triggering writeback
Date: Fri, 19 Nov 2010 10:06:41 -0500 [thread overview]
Message-ID: <20101119150641.GA5302@infradead.org> (raw)
In-Reply-To: <AANLkTinzhsvx=fx8dPpnJD_P70HKDRK+tWgFyYEN2_Zm@mail.gmail.com>
On Fri, Nov 19, 2010 at 08:42:05AM -0500, Theodore Tso wrote:
> My vote would be against. ? If you if you mmap a sparse file and then
> try writing to it willy-nilly, bad things will happen. ?This is true without
> a mlock(). ? Where is it written that mlock() has anything to do with
> improving this situation?
Exactly. Allocating space has been a side-effect on a handfull
filesystem for about 20 kernel releases.
> If userspace wants to call fallocate() before it calls mlock(), it should
> do that. ?And in fact, in most cases, userspace should probably be
> encouraged to do that. ? But having mlock() call fallocate() and
> then return ENOSPC if there's no room? Isn't it confusing that mlock()
> call ENOSPC? Doesn't that give you cognitive dissonance? It should
> because fundamentally mlock() has nothing to do with block allocation!!
> Read the API spec!
Indeed. There is no need to make mlock + flag a parallel-API to
fallocate.
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next prev parent reply other threads:[~2010-11-19 15:06 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-17 12:23 [PATCH 0/3] Avoid dirtying pages during mlock Michel Lespinasse
2010-11-17 12:23 ` Michel Lespinasse
2010-11-17 12:23 ` [PATCH 1/3] do_wp_page: remove the 'reuse' flag Michel Lespinasse
2010-11-17 12:23 ` Michel Lespinasse
2010-11-17 12:23 ` [PATCH 2/3] do_wp_page: clarify dirty_page handling Michel Lespinasse
2010-11-17 12:23 ` Michel Lespinasse
2010-11-17 12:23 ` [PATCH 3/3] mlock: avoid dirtying pages and triggering writeback Michel Lespinasse
2010-11-17 12:23 ` Michel Lespinasse
2010-11-17 12:57 ` Nick Piggin
2010-11-17 12:57 ` Nick Piggin
2010-11-17 15:28 ` Peter Zijlstra
2010-11-17 15:28 ` Peter Zijlstra
2010-11-17 22:05 ` Michel Lespinasse
2010-11-17 22:05 ` Michel Lespinasse
2010-11-17 22:18 ` Peter Zijlstra
2010-11-17 22:18 ` Peter Zijlstra
2010-11-17 23:11 ` Dave Chinner
2010-11-17 23:11 ` Dave Chinner
2010-11-17 23:31 ` Michel Lespinasse
2010-11-17 23:31 ` Michel Lespinasse
2010-11-19 1:46 ` Dave Chinner
2010-11-19 1:46 ` Dave Chinner
2010-11-17 23:52 ` Ted Ts'o
2010-11-17 23:52 ` Ted Ts'o
2010-11-18 0:53 ` Andrew Morton
2010-11-18 0:53 ` Andrew Morton
2010-11-18 11:03 ` Michel Lespinasse
2010-11-18 11:03 ` Michel Lespinasse
2010-11-18 13:37 ` Christoph Hellwig
2010-11-18 13:37 ` Christoph Hellwig
2010-11-18 17:41 ` Hugh Dickins
2010-11-18 17:41 ` Hugh Dickins
2010-11-19 7:23 ` Michel Lespinasse
2010-11-19 7:23 ` Michel Lespinasse
2010-11-19 13:38 ` Theodore Tso
2010-11-19 13:42 ` Theodore Tso
2010-11-19 13:42 ` Theodore Tso
2010-11-19 15:06 ` Christoph Hellwig [this message]
2010-11-19 15:06 ` Christoph Hellwig
2010-11-19 22:54 ` Andrew Morton
2010-11-19 22:54 ` Andrew Morton
2010-11-19 23:22 ` Ted Ts'o
2010-11-19 23:22 ` Ted Ts'o
2010-11-20 0:29 ` Dustin Kirkland
2010-11-19 23:31 ` Michel Lespinasse
2010-11-19 23:31 ` Michel Lespinasse
2010-11-19 23:54 ` Dave Chinner
2010-11-19 23:54 ` Dave Chinner
2010-11-18 5:46 ` Nick Piggin
2010-11-18 5:46 ` Nick Piggin
2010-11-18 10:43 ` Theodore Tso
2010-11-18 10:43 ` Theodore Tso
2010-11-18 13:39 ` Christoph Hellwig
2010-11-18 13:39 ` Christoph Hellwig
2010-11-18 18:00 ` Hugh Dickins
2010-11-18 18:00 ` Hugh Dickins
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