linux-ext4 - Re: [PATCH 2/4] ext4: fix reserved space transferring on chown() [V2]

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Message-ID: <20091209014259.GV27692@thunk.org>
Date:	Tue, 8 Dec 2009 20:42:59 -0500
From:	tytso@....edu
To:	Dmitry Monakhov <dmonakhov@...nvz.org>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/4] ext4: fix reserved space transferring on chown()
 [V2]

On Mon, Dec 07, 2009 at 10:41:15PM +0300, Dmitry Monakhov wrote:
> Absolutely right. I've fixed an issue, but overlooked the BIGGEST one.
> So off course my patch is wrong, even if we will acquire lock in
> different order " dqptr_sem > i_block_reservation_lock"
> we sill getting in to sleeping  spin lock problems by following scenario:
> ext4_da_update_reserve_space()
> ->dquot_claim_space()
> ASSUMES that we hold i_block_reservation_lock here.
> -->mark_dquot_dirty()
> --->ext4_write_dquot()
>     if (journalled quota) ext4_write_dquot();
> ---->dquot_commit()
> ----->mutex_lock(&dqopt->dqio_mutt's); <<< sleep here.
> 
> This means that we have fully redesign quota reservation locking. 
> As i already suggested previously here:
> http://thread.gmane.org/gmane.comp.file-systems.ext4/16576/focus=16587 

Given this, should I include this patch for now, given that it does
fix _one_ race, or should I hold off until you redo the locking?  How
long do you think to send a revised/new patch?

     	    	     	    		- Ted
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