linux-ext4 - Re: [PATCH 10/12] ext4: fix the number of credits needed for ext4_unlink() and ext4

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Date:	Mon, 11 Feb 2013 20:30:20 +0100
From:	Jan Kara <jack@...e.cz>
To:	Theodore Ts'o <tytso@....edu>
Cc:	Jan Kara <jack@...e.cz>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 10/12] ext4: fix the number of credits needed for
 ext4_unlink() and ext4_rmdir()

On Mon 11-02-13 13:30:36, Ted Tso wrote:
> On Mon, Feb 11, 2013 at 05:28:30PM +0100, Jan Kara wrote:
> > On Sat 09-02-13 16:53:50, Ted Tso wrote:
> > > The ext4_unlink() and ext4_rmdir() don't actually release the blocks
> > > associated with the file/directory.  This gets done in a separate jbd2
> > > handle called via ext4_evict_inode().  Thus, we don't need to reserve
> > > lots of journal credits for the truncate.
> > > 
> > > Note that using too many journal credits is non-optimal because it can
> > > leading to the journal transmit getting closed too early, before it is
> > > strictly necessary.
> >   Nice spotting. The patch looks good. You can add:
> > Reviewed-by: Jan Kara <jack@...e.cz>
> 
> The change in how ext4_unlink() works goes back years and years, so
> this patch is applicable to ext3 as well.  I imagine a some of these
> patches, such as the one where we now can start the handle in
> ext4_new_inode(), or changing the order in which we call
> grab_cache_page() and journal_start(), will probably be too
> complicated for you to feel comfortable backporting them to ext3.
> This one is really simple though, so maybe it's worth it.
> 
> The other ones you might want to consider is the patches do the
> directory lookup before before start the journal, since they are
> pretty easy to validate by inspection.
  Yeah, I will likely take the easy ones into ext3 but I definitely don't
plan to port the change in ext4_new_inode() into ext3.

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