From: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Subject: Re: [RFC][PATCH] ext3: don't read inode block if the buffer has a
    write error
Date: Tue, 24 Jun 2008 22:03:56 +0900
Message-ID: <4860F0BC.1090404@hitachi.com>
References: <485F8822.5030205@hitachi.com>
    <20080623191733.52c3491c.akpm@linux-foundation.org>
    <alpine.LFD.1.10.0806231958010.2926@woody.linux-foundation.org>
    <200806241317.22470.nickpiggin@yahoo.com.au>
    <alpine.LFD.1.10.0806232039300.2926@woody.linux-foundation.org>
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Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
	Andrew Morton <akpm@linux-foundation.org>, sct@redhat.com,
	adilger@sun.com, linux-kernel@vger.kernel.org,
	linux-ext4@vger.kernel.org, jack@suse.cz,
	sugita <yumiko.sugita.yf@hitachi.com>,
	Satoshi OSHIMA <satoshi.oshima.fk@hitachi.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
In-Reply-To: <alpine.LFD.1.10.0806232039300.2926@woody.linux-foundation.org>
Sender: linux-ext4-owner@vger.kernel.org

Hi all,

Thank you for precious comments.

Linus Torvalds wrote:

> 
> On Tue, 24 Jun 2008, Nick Piggin wrote:
> 
>>What you want to do is not insane, but the way it is currently being
>>done is. As I said, just clearing the uptodate bit might blow up your
>>kernel pretty quickly from assertions in the vm. It should be going
>>through the whole truncate or invalidate page machinery in order to
>>do that.
> 
> Fair enough.
> 
> I would not mind, for example, leaving the uptodate bit, but removing it 
> from the radix tree or something like that (ie turning it into an 
> anonymous page for a page-cache page, just removing it from the 
> hash-queues for a buffer_head).

If we move page caches with errors to another radix tree instead of
just removing, we may be able to do special handlings: rewrite once,
or check the page caches and get rid of them from user space, and so on.
 
> Of course, that could cause other problems (eg any VM assertions that 
> shared mappings only contain non-anon pages).

As Jan and Nick stated, this seems to need a great effort, but I think
it is worthwhile to do.

Thanks,
-- 
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center