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 13:30:36 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	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, 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.

Cheers,

						- Ted
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