linux-ext4 - Re: [PATCH] ext4: restart ext4_ext_remove_space() after transaction restart V2

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Message-ID: <20100526144545.GD29528@thunk.org>
Date:	Wed, 26 May 2010 10:45:45 -0400
From:	tytso@....edu
To:	Dmitry Monakhov <dmonakhov@...nvz.org>
Cc:	linux-ext4@...r.kernel.org, jack@...e.cz,
	aneesh.kumar@...ux.vnet.ibm.com
Subject: Re: [PATCH] ext4: restart ext4_ext_remove_space() after
 transaction restart V2

On Wed, May 26, 2010 at 06:23:55PM +0400, Dmitry Monakhov wrote:
> 
> Later if we face a needs to restart transaction which result in
> i_data_sem indernal drop/acquire.
> And when the sem was dropped new block may be allocated by a
> flusher task (delay allocation writeback in the middle of the file)
> 
> *Flusher* will discover than STATE_EXT_TRUNC is set and clear it
> is allocation is really necessary(EXT4_GET_BLOCKS_CREATE is set)
> By clearing STATE_EXT_TRUNC bit flusher let truncate task to know
> what it have to restart it's job. 

OK, but why not have the truncate *always* restart its job after
restarting the transaction?  #1, it's relatively rare in most
workloads that we need to restart the transaction at all in the first
place, and #2, it's easier to test if we always restart the truncate,
and #3, it's not like we'll be doing that much extra work if we
restart the truncate and the file wasn't extended significantly...

	    	     	     	  - Ted
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