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

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Date:	Fri, 20 Nov 2009 22:27:32 +0100
From:	Jan Kara <jack@...e.cz>
To:	Jan Blunck <jblunck@...e.de>
Cc:	linux-fsdevel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linux-Kernel Mailinglist <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>, jkacur@...hat.com,
	Arnd Bergmann <arnd@...db.de>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Jamie Lokier <jamie@...reable.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Petr Vandrovec <vandrove@...cvut.cz>,
	Anders Larsen <al@...rsen.net>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH 13/15] Do not fallback to default_llseek() when
 readdir() uses BKL

On Fri 20-11-09 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>
> ---
>  fs/udf/dir.c              |    1 +
For the UDF part:

  Acked-by: Jan Kara <jack@...e.cz>

-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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