linux-ext4 - Re: RFC PATCH: ext4 no journal corruption with locale-gen

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Message-ID: <20090617234604.GF7867@mit.edu>
Date:	Wed, 17 Jun 2009 19:46:04 -0400
From:	Theodore Tso <tytso@....edu>
To:	Curt Wohlgemuth <curtw@...gle.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: RFC PATCH: ext4 no journal corruption with locale-gen

Hi Curt,

Thanks for your analysis of the bug.  The reason for the strange logic
in ext4_set_aops() is because at the moment the code doesn't support
the combination of data=journalled && delalloc.  That's why it was
explicitly checking for ext4_should_order_data() and
ext4_should_writeback_data().

We have a check for this in ext4_fill_super(), so your patch should be
safe, since the combination of ext4_should_journal_data &&
test_opt(inode->i_sb, DELALLOC) should never happen.

As to your question of whether the nodelalloc and nojournal case
should really be ext4_journalled_aops, I suspect ext4_writeback_aops
makes more sense.  I haven't audited all of the code paths to make
sure they DTRT in the non-journalled case yet, though.

							- Ted
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