linux-kernel - Re: [PATCH] namei: revert old behaviour for filename_lookup with LOOKUP

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Message-ID: <20161013200602.GR19539@ZenIV.linux.org.uk>
Date:   Thu, 13 Oct 2016 21:06:02 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Vineeth Remanan Pillai <vineethp@...zon.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kamatam@...zon.com, aliguori@...zon.com
Subject: Re: [PATCH] namei: revert old behaviour for filename_lookup with
 LOOKUP_PARENT flag

On Thu, Oct 13, 2016 at 07:58:51PM +0000, Vineeth Remanan Pillai wrote:
> filename_lookup used to return success for non-existing file when called
> with LOOKUP_PARENT flag. This behaviour was changed with
> commit 8bcb77fabd7c ("namei: split off filename_lookupat()
> with LOOKUP_PARENT")
> 
> The above patch split parent lookup functionality to a different function
> filename_parentat and changed all calls to filename_lookup(LOOKUP_PARENT)
> to the new function filename_parentat. But functions like kern_path which
> passed the flags directly to filename_lookup regressed due to this.
> 
> This patch aims to fix the regressed behaviour by calling
> filename_parentat from filename_lookup if the flags contain LOOKUP_PARENT.

What would we want that for?  Details, please.  In particular, I would like
to know how to use that in non-racy way.  What are you doing with it?

PS: "regressed" assumes that there had been any promise of API stability;
no such thing has ever existed.