Re: [PATCH] remove BKL from ext2's readdir

[Andrew Morton]

Alex Tomas <[e-mail]> wrote:
>
> 
> hi!
> 
> I took a look at readdir() in 2.5.64's ext2 and found it serialized by BKL.

Yes, I had this in -mm for ages, seem to have lost it.  Also removal of BKL
from lseek().

The theory is that the lock is there to avoid f_pos races against lseek.  We
ended up deciding that the way to address this is to ensure that all readdir
implementations do:

foo_readdir()
{
	loff_t pos = file->f_pos;

	....
	<code which doesn't touch file->f_pos, but which modifies pos>
	...

	file->f_pos = pos;
}

ext2 does this right and does not need the lock_kernel().  Once all
filesystems have been audited (and, if necessary, fixed) we can remove the
BKL from lseek also.