linux-kernel - Re: [PATCH 03/34] teach move_mount(2) to work with OPEN_TREE

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Message-ID: <7833.1539893347@warthog.procyon.org.uk>
Date:   Thu, 18 Oct 2018 21:09:07 +0100
From:   David Howells <dhowells@...hat.com>
To:     Alan Jenkins <alan.christopher.jenkins@...il.com>
Cc:     dhowells@...hat.com, viro@...iv.linux.org.uk,
        torvalds@...ux-foundation.org, ebiederm@...ssion.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        mszeredi@...hat.com
Subject: Re: [PATCH 03/34] teach move_mount(2) to work with OPEN_TREE_CLONE [ver #12]

Alan Jenkins <alan.christopher.jenkins@...il.com> wrote:

> If I instead do the mount+unmount first, and close the FD as a second step, I
> think there's a lockup in the close().  The lockup happens in the same place
> as the unmount lockup from before. (Except there's a line "Code: Bad RIP
> value", I don't know why that happens).

Sorry, which FD are we talking about?

I presume you're talking about a command sequence like this:

	# unshare --mount
	# test-fsmount
	# mount --move . /mnt
	# mount --move /mnt /mnt
	# cd
	# umount /mnt
	# exit

but this fails on your modified test-fsmount with:

	shell-init: error retrieving current directory: getcwd: cannot access
	parent directories: No such file or directory

David