linux-kernel - Re: [PATCH 13/15] Do not fallback to default

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Date:	Sat, 21 Nov 2009 19:03:54 +0100
From:	Anders Larsen <al@...rsen.net>
To:	Jan Blunck <jblunck@...e.de>
Cc:	linux-fsdevel@...r.kernel.org,
	Linux-Kernel Mailinglist <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 13/15] Do not fallback to default_llseek() when
 readdir() uses BKL

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@...e.de>
> ---

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