linux-ext4 - Re: [PATCH] ext4: Fix potential quota deadlock

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Date:	Thu, 10 Dec 2009 17:25:34 +0100
From:	Jan Kara <jack@...e.cz>
To:	Dmitry Monakhov <dmonakhov@...nvz.org>
Cc:	linux-ext4@...r.kernel.org, cmm@...ibm.com
Subject: Re: [PATCH] ext4: Fix potential quota deadlock

> We have to delay vfs_dq_claim_space() until allocation context destruction.
> Currently we have following call-trace:
> ext4_mb_new_blocks()
>   /* task is already holding ac->alloc_semp */
>  ->ext4_mb_mark_diskspace_used
>     ->vfs_dq_claim_space()  /*  acquire dqptr_sem here. Possible deadlock */
>  ->ext4_mb_release_context() /* drop ac->alloc_semp here */
> 
> Let's move quota claiming to ext4_da_update_reserve_space()
> This movement already discussed and approved during discussion
> write() vs chown() race condition.
  The patch looks good to me.

Acked-by: Jan Kara <jack@...e.cz>

									Honza

-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs
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