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Date:   Tue, 3 Sep 2019 14:31:34 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Qian Cai <cai@lca.pw>
Cc:     linux-fsdevel@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: "fs/namei.c: keep track of nd->root refcount status" causes boot
 panic
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 <20190903123719.GF1131@ZenIV.linux.org.uk>
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On Tue, Sep 03, 2019 at 01:37:19PM +0100, Al Viro wrote:
> On Tue, Sep 03, 2019 at 12:21:36AM -0400, Qian Cai wrote:
> > The linux-next commit "fs/namei.c: keep track of nd->root refcount status” [1] causes boot panic on all
> > architectures here on today’s linux-next (0902). Reverted it will fix the issue.
> 
> <swearing>
> 
> OK, I see what's going on.  Incremental to be folded in:

... or, better yet,

diff --git a/include/linux/namei.h b/include/linux/namei.h
index 20ce2f917ef4..397a08ade6a2 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -37,7 +37,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
 #define LOOKUP_NO_REVAL		0x0080
 #define LOOKUP_JUMPED		0x1000
 #define LOOKUP_ROOT		0x2000
-#define LOOKUP_ROOT_GRABBED	0x4000
+#define LOOKUP_ROOT_GRABBED	0x0008
 
 extern int path_pts(struct path *path);
 

to avoid breaking out-of-tree stuff for now good reason.
Folded and pushed out.