From: Jan Kara <jack@suse.cz>
To: linux-ext4@vger.kernel.org
Cc: Ted Tso <tytso@mit.edu>
Subject: Journal async commit broken for data=ordered?
Date: Tue, 14 Feb 2012 16:55:36 +0100 [thread overview]
Message-ID: <20120214155536.GA16561@quack.suse.cz> (raw)
Hello,
I've just realized that JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT breaks
guarantees of data=ordered mode in ext4. The problem is that async commit
code assumes that when a checksum of a transaction in the journal matches,
all necessary data is on disk. This is true for metadata but need not be so
for data - the whole transaction may be correctly on pernament storage
while some data is still sitting in drive's caches. Thus if a power failure
happens at that moment, we have broken guarantees of data=ordered mode.
Seeing that async commit code isn't used by default anyway (I remember
there used to be some problems with it), shouldn't we just rip it out?
Honza
next reply other threads:[~2012-02-14 15:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-14 15:55 Jan Kara [this message]
2012-02-14 20:56 ` Journal async commit broken for data=ordered? Andreas Dilger
2012-02-15 15:57 ` Jan Kara
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