From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags
Date: Fri, 12 Jul 2019 16:00:27 +0100
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Cc: Jeff Layton <jlayton@kernel.org>, "J. Bruce Fields" <bfields@fieldses.org>, Arnd Bergmann <arnd@arndb.de>, David Howells <dhowells@redhat.com>, Shuah Khan <shuah@kernel.org>, Shuah Khan <skhan@linuxfoundation.org>, Christian Brauner <christian@brauner.io>, David Drysdale <drysdale@google.com>, Andy Lutomirski <luto@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Eric Biederman <ebiederm@xmission.com>, Andrew Morton <akpm@linux-foundation.org>, Alexei Starovoitov <ast@kernel.org>, Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>, Tycho Andersen <tycho@tycho.ws>, Chanho Min <chanho.min@lge.com>, Oleg Nesterov <oleg@redhat.com>, Aleksa Sarai <asarai@suse.de>, containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org
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On Fri, Jul 12, 2019 at 02:25:53PM +0100, Al Viro wrote:

> 	if (flags & LOOKUP_BENEATH) {
> 		nd->root = nd->path;
> 		if (!(flags & LOOKUP_RCU))
> 			path_get(&nd->root);
> 		else
> 			nd->root_seq = nd->seq;

BTW, this assignment is needed for LOOKUP_RCU case.  Without it
you are pretty much guaranteed that lazy pathwalk will fail,
when it comes to complete_walk().

Speaking of which, what would happen if LOOKUP_ROOT/LOOKUP_BENEATH
combination would someday get passed?