Date: Sun, 20 Mar 2016 01:55:11 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>, Dave Chinner <david@fromorbit.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-aio@kvack.org, linux-mm <linux-mm@kvack.org>
Subject: Re: aio openat Re: [PATCH 07/13] aio: enabled thread based async
 fsync
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On Sat, Mar 19, 2016 at 06:45:19PM -0700, Linus Torvalds wrote:

> It actually does seem to do that, although in an admittedly rather
> questionable way.
> 
> I think it should use path_openat() rather than do_filp_open(), but
> passing in LOOKUP_RCU to do_filp_open() actually does work: it just
> means that the retry after ECHILD/ESTALE will just do it *again* with
> LOOKUP_RCU. It won't fall back to non-rcu mode, it just won't or in
> the LOOKUP_RCU flag that is already set.

What would make unlazy_walk() fail?  And if it succeeds, you are not
in RCU mode anymore *without* restarting from scratch...