linux-ext4 - Re: [PATCH v2] Adding support to freeze and unfreeze a journal

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Message-ID: <20110509095313.GB4122@quack.suse.cz>
Date:	Mon, 9 May 2011 11:53:13 +0200
From:	Jan Kara <jack@...e.cz>
To:	Surbhi Palande <surbhi.palande@...onical.com>
Cc:	adilger.kernel@...ger.ca, jack@...e.cz,
	toshi.okajima@...fujitsu.com, tytso@....edu,
	m.mizuma@...fujitsu.com, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, sandeen@...hat.com
Subject: Re: [PATCH v2] Adding support to freeze and unfreeze a journal

On Sat 07-05-11 23:04:22, Surbhi Palande wrote:
> +void jbd2_journal_thaw(journal_t * journal)
> +{
> +	write_lock(&journal->j_state_lock);
> +	journal->j_flags = journal->j_flags &= ~JBD2_FROZEN;
> +	write_unlock(&journal->j_state_lock);
> +	smp_wmb();
  Why is here the smp_wmb()? The write is inside a rw-lock so it cannot be
reordered. Also wake_up() is protected by queue->lock so I don't see the
need for a barrier.

> +	wake_up(&journal->j_wait_frozen);
> +}
> +EXPORT_SYMBOL(jbd2_journal_thaw);

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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