linux-kernel - Re: EXT4 ENOSPC Bug

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Message-ID: <20090217220029.GS23758@mini-me.lan>
Date:	Tue, 17 Feb 2009 17:00:29 -0500
From:	Theodore Tso <tytso@....edu>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	Andres Freund <andres@...razel.de>,
	Alex Buell <alex.buell@...ted.org.uk>, adilger@....com,
	LKML <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org,
	Jonathan Bastien-Filiatrault <joe@....org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: EXT4 ENOSPC Bug

On Tue, Feb 17, 2009 at 02:08:21PM -0600, Eric Sandeen wrote:
> FWIW my problem seems to be different than others have encountered; mine
> persists past reboot, while other reporters have said that a reboot
> (remount) makes the problem go away.

It might or might not be the same problem, since the reporters were
doing this on a mounted root partition, and on a filesystem quite a
bit larger than your test filesystem; so it could be that the act of
shutting down and rebooting created/deleted various pid files, and
purturbed the filesystem to make the problem go away.

The other possibility is that it is the flex_bg specific counters
which were introduced specifically for find_group_flex.  I'm not wild
about them since they mean we have to take an extra flex_bg specific
spin lock for every block and inode allocation.  The Orlov algorithm
only needs the information when allocating directories, and since
those are rarer than file allocations, I think it should be OK to
simply sum up the necessary fields at directory allocation time
instead of trying to maintain separate counters (which could possibly
get corrupted, although I couldn't see a way that they could be
getting out of sync with reality).

					- Ted
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