linux-kernel - Re: ext3/ext4 directories don't shrink after deleting lots of files

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Message-Id: <1242408544.6933.687.camel@timo-desktop>
Date:	Fri, 15 May 2009 13:29:04 -0400
From:	Timo Sirainen <tss@....fi>
To:	Theodore Tso <tytso@....edu>
Cc:	Josef Bacik <josef@...icpanda.com>, linux-kernel@...r.kernel.org
Subject: Re: ext3/ext4 directories don't shrink after deleting lots of files

On Fri, 2009-05-15 at 06:58 -0400, Theodore Tso wrote:
> > I was rather thinking something that I could run while the system was  
> > fully operational. Otherwise just moving the files to a temp directory + 
> > rmdir() + rename() would have been fine too.
> >
> > I just tested that xfs, jfs and reiserfs all shrink the directories  
> > immediately. Is it more difficult to implement for ext* or has no one  
> > else found this to be a problem?
> 
> It's probably fairest to say no one has thought it worth the effort.

My problem is with mail servers and Maildir format where it's possible
that a user has tons of emails and wants to delete them. The mailbox
maybe slowly grows back to the huge size, but in the meantime it's
slower than necessary.

I can't really fix those directories while the system is running because
mail reading doesn't use any locking (and adding locking would be
unnecessary overhead). Writing does use locking though, so I could
create a new duplicate directory and switch it with the original
directory. But I suppose there's no way to atomically replace (or swap)
a non-empty directory with another?

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