linux-ext4 - Re: [PATCH v3]Ext4: journal credits reservation fixes for DIO, fallocate and delalloc writepages

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Date:	Mon, 04 Aug 2008 13:23:53 +0200
From:	Frédéric Bohé <frederic.bohe@...l.net>
To:	Theodore Tso <tytso@....edu>
Cc:	Mingming Cao <cmm@...ibm.com>,
	Shehjar Tikoo <shehjart@....unsw.edu.au>,
	linux-ext4@...r.kernel.org,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Andreas Dilger <adilger@....com>
Subject: Re: [PATCH v3]Ext4: journal credits reservation fixes for DIO,
	fallocate and delalloc writepages

Le vendredi 01 août 2008 à 20:03 -0400, Theodore Tso a écrit :
> In any case, I figurd out why my patch wasn't enough.  There was a bug
> in ext4_ext_journal_restart:
> 
> int ext4_ext_journal_restart(handle_t *handle, int needed)
> {
> 	int err;
> 
> 	if (handle->h_buffer_credits > needed)
> 		return 0;
> 	err = ext4_journal_extend(handle, needed);
> 	if (err)
> 		return err;
> 	return ext4_journal_restart(handle, needed);
> }
> 
> This is buggy; ext4_journal_extend returns < 0 on an error, 0 if the
> handle was successfully extended without needing a journal restart,
> and > 0 if the ext4_journal_restart() needs to be called.  So the
> current code returns a failure and doesn't restart the journal when it
> is needed, and calls ext4_journal_restart() needlessly when it is not
> needed and the handle could be extended without closing the current
> transaction.
> 
> The fix is a simple one-liner:
> 
> int ext4_ext_journal_restart(handle_t *handle, int needed)
> {
> 	int ret;
> 
> 	if (handle->h_buffer_credits > needed)
> 		return 0;
> 	err = ext4_journal_extend(handle, needed);
> 	if (ret < = 0)
> 		return ret;
> 	return ext4_journal_restart(handle, needed);
> }
> 
> This seems to indicate ext4_ext_journal_restart() has never been
> called in anger by the ext4_ext_truncate() code.  We may want to
> double check it with a really big, mongo extent tree and make sure it
> does the right thing one of these days.
> 
> 							- Ted
> 

FYI, I have just tried this fix, and i don't see the "orphan list check
failed" messages any more.

Fred




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