linux-ext4 - Re: [PATCH] ext4: fix ext4_evict_inode() racing against workqueue processing code

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Message-ID: <20130320133751.GC12865@thunk.org>
Date:	Wed, 20 Mar 2013 09:37:51 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: fix ext4_evict_inode() racing against workqueue
 processing code

On Wed, Mar 20, 2013 at 02:22:23PM +0100, Jan Kara wrote:
> > +	if (work_pending(&EXT4_I(inode)->i_unwritten_work))
> > +		flush_work(&EXT4_I(inode)->i_unwritten_work);
> >  }
>   Won't it be more logical to use cancel_work_sync() here?

Hmm.... yes, probably, but then ext4_ioend_wait() can only be safely
used by ext4_evict_inode().  I'll make the change, but I'll also make
a comment to this effect.  (No one else is using it now, but if there
was ever a need to use it while the inode was in use, using
cancel_work_sync() would be highly dagernous/racy.  That being said, I
can't really think of a good use case other than evict_inode path, so
it seems fine to make this change.)

					- Ted
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