From: Jens Axboe <axboe@suse.de>
To: Nick Piggin <npiggin@suse.de>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@osdl.org>,
Christoph Lameter <clameter@engr.sgi.com>,
Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [patch] rfc: fix splice mapping race?
Date: Mon, 19 Jun 2006 09:29:22 +0200 [thread overview]
Message-ID: <20060619072921.GA4466@suse.de> (raw)
In-Reply-To: <20060618094157.GD14452@wotan.suse.de>
On Sun, Jun 18 2006, Nick Piggin wrote:
> Hi, I would be interested in confirmation/comments for this patch.
>
> I believe splice is unsafe to access the page mapping obtained
> when the page was unlocked: the page could subsequently be truncated
> and the mapping reclaimed (see set_page_dirty_lock comments).
>
> Modify the remove_mapping precondition to ensure the caller has
> locked the page and obtained the correct mapping. Modify callers to
> ensure the mapping is the correct one.
>
> In page migration, detect the missing mapping early and bail out if
> that is the case: the page is not going to get un-truncated, so
> retrying is just a waste of time.
splice bit looks good to me!
--
Jens Axboe
WARNING: multiple messages have this Message-ID (diff)
From: Jens Axboe <axboe@suse.de>
To: Nick Piggin <npiggin@suse.de>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@osdl.org>,
Christoph Lameter <clameter@engr.sgi.com>,
Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [patch] rfc: fix splice mapping race?
Date: Mon, 19 Jun 2006 09:29:22 +0200 [thread overview]
Message-ID: <20060619072921.GA4466@suse.de> (raw)
In-Reply-To: <20060618094157.GD14452@wotan.suse.de>
On Sun, Jun 18 2006, Nick Piggin wrote:
> Hi, I would be interested in confirmation/comments for this patch.
>
> I believe splice is unsafe to access the page mapping obtained
> when the page was unlocked: the page could subsequently be truncated
> and the mapping reclaimed (see set_page_dirty_lock comments).
>
> Modify the remove_mapping precondition to ensure the caller has
> locked the page and obtained the correct mapping. Modify callers to
> ensure the mapping is the correct one.
>
> In page migration, detect the missing mapping early and bail out if
> that is the case: the page is not going to get un-truncated, so
> retrying is just a waste of time.
splice bit looks good to me!
--
Jens Axboe
--
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next prev parent reply other threads:[~2006-06-19 7:28 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-06-18 9:41 [patch] rfc: fix splice mapping race? Nick Piggin
2006-06-18 9:41 ` Nick Piggin
2006-06-18 10:02 ` Peter Zijlstra
2006-06-18 10:02 ` Peter Zijlstra
2006-06-18 10:11 ` Nick Piggin
2006-06-18 10:11 ` Nick Piggin
2006-06-19 7:29 ` Jens Axboe [this message]
2006-06-19 7:29 ` Jens Axboe
2006-06-19 15:35 ` Christoph Lameter
2006-06-19 15:35 ` Christoph Lameter
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