linux-ext4 - Re: [RFC][PATCH] Re: [BUG] ext4: cannot unfreeze a filesystem due to a deadlock

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Date:	Mon, 02 May 2011 09:01:50 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	surbhi.palande@...ntu.com
CC:	Jan Kara <jack@...e.cz>, Dave Chinner <david@...morbit.com>,
	Toshiyuki Okajima <toshi.okajima@...fujitsu.com>,
	"Ted Ts'o" <tytso@....edu>,
	Masayoshi MIZUMA <m.mizuma@...fujitsu.com>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC][PATCH] Re: [BUG] ext4: cannot unfreeze a filesystem due
 to a deadlock

On 5/2/11 7:30 AM, Surbhi Palande wrote:

...

> Yes, but ext4_freeze() also calls jbd2_journal_unlock_updates(journal) which decrements the  j_barrier_count (which was previously updated/incremented in jbd2_journal_lock_updates) ? before it returns. So after this call a new transaction/handle can be accepted/started.
> 
> A comment in ext4_freeze() says:
> /* we rely on s_frozen to stop further updates */
> (before calling jbd2_journal_unlock_updates())

that was me; 

commit 6b0310fbf087ad6e9e3b8392adca97cd77184084
Author: Eric Sandeen <sandeen@...hat.com>
Date:   Sun May 16 02:00:00 2010 -0400

    ext4: don't return to userspace after freezing the fs with a mutex held


otherwise we return to userspace holding a mutex :(

-Eric
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