linux-kernel - Re: [PATCH 16/23] initramfs: simplify clean

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Message-ID: <20200727024426.GI23808@casper.infradead.org>
Date:   Mon, 27 Jul 2020 03:44:26 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Christoph Hellwig <hch@....de>,
        Lukasz Stelmach <l.stelmach@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
        Song Liu <song@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-raid@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Shaohua Li <shli@...com>
Subject: Re: [PATCH 16/23] initramfs: simplify clean_rootfs

On Mon, Jul 27, 2020 at 03:41:49AM +0100, Al Viro wrote:
> On Thu, Jul 23, 2020 at 04:27:34PM +0200, Christoph Hellwig wrote:
> > On Thu, Jul 23, 2020 at 04:25:34PM +0200, Lukasz Stelmach wrote:
> > > >> Can you comment out the call to d_genocide?  It seems like for your
> > > >> the fact that clean_rootfs didn't actually clean up was a feature and
> > > >> not a bug.
> > > >> 
> > > >> I guess the old, pre-2008 code also wouldn't have worked for you in
> > > >> that case.
> > > >
> > > > Did you get a chance to try this?
> > > 
> > > Indeed, commenting out d_genocide() helps.
> > 
> > So given that people have relied on at least the basic device nodes
> > like /dev/console to not go away since 2008, I wonder if we should just
> > remove clean_rootfs entirely
> > 
> > Linus, Al?
> 
> First of all, d_genocide() is simply wrong here from VFS point of view.  _IF_
> you want recursive removal, you need simple_recursive_remove(path.dentry, NULL).
> And it's a userland-visible change of behaviour.
> 
> As for removal of clean_rootfs()...  FWIW, the odds of an image that would
> eventually fail accidentally getting past the signature mismatch check are
> fairly low.  I've no idea what scenario the author of that thing used to have;
> that would be Shaohua Li <shaohua.li@...el.com>.  Cc'd...

Shaohua is now at Facebook.