Date: Tue, 12 Dec 2006 01:52:32 -0800
From: Andrew Morton <akpm@osdl.org>
To: Dmitriy Monakhov <dmonakhov@sw.ru>
Cc: Dmitriy Monakhov <dmonakhov@openvz.org>, linux-kernel@vger.kernel.org,
       Linux Memory Management <linux-mm@kvack.org>, <devel@openvz.org>,
       xfs@oss.sgi.com
Subject: Re: [PATCH]  incorrect error handling inside
 generic_file_direct_write
Message-Id: <20061212015232.eacfbb46.akpm@osdl.org>
In-Reply-To: <87bqm9tie3.fsf@sw.ru>
References: <87k60y1rq4.fsf@sw.ru>
	<20061211124052.144e69a0.akpm@osdl.org>
	<87bqm9tie3.fsf@sw.ru>
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On Tue, 12 Dec 2006 15:20:52 +0300
Dmitriy Monakhov <dmonakhov@sw.ru> wrote:

> > XFS (at least) can call generic_file_direct_write() with i_mutex not held. 
> > And vmtruncate() expects i_mutex to be held.
> >
> > I guess a suitable solution would be to push this problem back up to the
> > callers: let them decide whether to run vmtruncate() and if so, to ensure
> > that i_mutex is held.
> >
> > The existence of generic_file_aio_write_nolock() makes that rather messy
> > though.
> This means we may call generic_file_aio_write_nolock() without i_mutex, right?
> but call trace is :
>   generic_file_aio_write_nolock() 
>   ->generic_file_buffered_write() /* i_mutex not held here */ 
> but according to filemaps locking rules: mm/filemap.c:77
>  ..
>  *  ->i_mutex			(generic_file_buffered_write)
>  *    ->mmap_sem		(fault_in_pages_readable->do_page_fault)
>  ..
> I'm confused a litle bit, where is the truth? 

xfs_write() calls generic_file_direct_write() without taking i_mutex for
O_DIRECT writes.

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