linux-kernel - Re: [experimental PATCH] ovl: get rid of d

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Date:   Fri, 15 Sep 2017 15:07:34 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>
Subject: Re: [experimental PATCH] ovl: get rid of d_real()

On Fri, Sep 15, 2017 at 03:58:05PM +0200, Miklos Szeredi wrote:
> And here's the prototype.  Poof, d_real() is gone.
> 
> It definitely has got problems, but just maybe it can be made better than the
> current mess.  It *does* solve the ro-rw inconsistency for normal reads (not
> mmaps).

... and makes for mind-boggling amount of opening/closing the files on underlying
filesystem.  Doing that on sodding ->read_iter() is simply wrong.  And you are
using the wrong credentials for those opens, anyway - it should be creds of opener,
not reader.