Date: Sat, 21 Nov 2009 19:03:54 +0100
From: Anders Larsen <al@alarsen.net>
Subject: Re: [PATCH 13/15] Do not fallback to default_llseek() when
 readdir() uses BKL
To: Jan Blunck <jblunck@suse.de>
Cc: linux-fsdevel@vger.kernel.org,
       Linux-Kernel Mailinglist <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>
References: <1258735245-25826-1-git-send-email-jblunck@suse.de>
	<1258735245-25826-14-git-send-email-jblunck@suse.de>
In-Reply-To: <1258735245-25826-14-git-send-email-jblunck@suse.de> (from
	jblunck@suse.de on Fri Nov 20 17:40:43 2009)
Message-Id: <1258826634l.13034l.0l@oscar.alarsen.net>
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On 2009-11-20 17:40:43, Jan Blunck wrote:
> Do not use the fallback default_llseek() if the readdir operation of  
> the
> filesystem still uses the big kernel lock. Since llseek() modifies
> file->f_pos of the directory directly it may need locking to not  
> confuse
> readdir which usually uses file->f_pos directly as well. Since the  
> special
> characteristics of the BKL (unlocked on schedule) are not necessary  
> in this
> case, the inode mutex can be used for locking as provided by
> generic_file_llseek(). This is only possible since all filesystems,  
> except
> reiserfs, either use a directory as a flat file or with disk address
> offsets. Reiserfs on the other hand uses a 32bit hash off the  
> filename as
> the offset so generic_file_llseek() can get used as well since the  
> hash is
> always smaller than sb->s_maxbytes (= (512 << 32) - blocksize).
> 
> Signed-off-by: Jan Blunck <jblunck@suse.de>
> ---

wrt fs/qnx4:
Acked-by: Anders Larsen <al@alarsen.net>
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