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Date: Mon, 6 Nov 2017 13:33:04 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Jan Kara <jack@suse.cz>
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Subject: Re: possible deadlock in generic_file_write_iter
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On Mon, Nov 06, 2017 at 02:15:44PM +0100, Jan Kara wrote:

> > Should we annotate these inodes with different lock types? Or use
> > nesting annotations?
> 
> Well, you'd need to have a completely separate set of locking classes for
> each filesystem to avoid false positives like these. And that would
> increase number of classes lockdep has to handle significantly. So I'm not
> sure it's really worth it...

Especially when you consider that backing file might be on a filesystem
that lives on another loop device.  *All* per-{device,fs} locks involved
would need classes split that way...