Message-ID: <446C2F89.5020300@bull.net>
Date: Thu, 18 May 2006 10:25:45 +0200
From: Zoltan Menyhart <Zoltan.Menyhart@bull.net>
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To: jack@suse.cz, sct@redhat.com, linux-kernel@vger.kernel.org
Subject: re: [PATCH] Change ll_rw_block() calls in JBD
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> We must be sure that the current data in buffer are sent to disk.
> Hence we have to call ll_rw_block() with SWRITE.

Let's consider the following case:

	while (commit_transaction->t_sync_datalist) {
		...

		// Assume a "bh" got locked before starting this loop

		if (buffer_locked(bh)) {
			...
			__journal_temp_unlink_buffer(jh);
			__journal_file_buffer(jh, commit_transaction, BJ_Locked);
		} else ...
	}
	...
	while (commit_transaction->t_locked_list) {
		...

		// Assume our "bh" is not locked any more
		// Nothing has happened to this "bh", someone just wanted
		// to look at it in a safe way

		if (buffer_jbd(bh) && jh->b_jlist == BJ_Locked) {
			__journal_unfile_buffer(jh);
			jbd_unlock_bh_state(bh);
			journal_remove_journal_head(bh);
			put_bh(bh);
		} else ...
	}

I.e. having an already locked "bh", it is missed out from the log.

Regards,

Zoltan Menyhart

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