Re: [Ext2-devel] [PATCH] concurrent block allocation for ext2 against 2.5.64

[Andreas Dilger <adilger@clusterfs.com>]

On Mar 13, 2003  14:23 -0500, Theodore Ts'o wrote:
> On Thu, Mar 13, 2003 at 10:39:48AM -0700, Andreas Dilger wrote:
> > Sadly, we are constantly diverging the ext2/ext3 codebases.  Lots of
> > features are going into ext3, but lots of fixes/improvements are only
> > going into ext2.  Is ext3 holding BKL for doing journal_start() still?
> > 
> > Looking at ext3_prepare_write() we grab the BKL for doing journal_start()
> > and for journal_stop(), but I don't _think_ we need BKL for journal_stop()
> > do we?  We may or may not need it for the journal_data case, but that is
> > not even working right now I think.
> 
> We badly need to remove the BKL from ext3; it's the source of massive
> performance problems for ext3 on larger machines.  
> 
> Stephen, you were telling me a week or two ago that there were some
> subtle issues involved with BKL removal from the jbd layer --- could
> you give us a quick summary of what landminds are there for whoever
> wants to try to tackle the ext3/jbd BKL removal?

Ted, as a start, we can move the (un)lock_kernel() calls from the ext3
code into the journal_start() and journal_stop(), and then continue to
push it down into the places where we need it and/or replace it with a
better lock.  This not only makes the lock migration easier, but also
ensures that we always have the lock when we need it.

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/