linux-kernel - Re: [cgroup or VFS ?] INFO: possible recursive locking detected

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Date:	Tue, 10 Feb 2009 11:06:39 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Al Viro <viro@...IV.linux.org.uk>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <menage@...gle.com>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [cgroup or VFS ?] INFO: possible recursive locking detected

> It seems to me we can simply put the new s_umount instance in a
> different subclass. Its a bit unusual to use _nested for the outer lock,
> but lockdep doesn't particularly cares about subclass order.
> 
> If there's any issue with the callers of sget() assuming the s_umount
> lock being of sublcass 0, then there is another annotation we can use to
> fix that, but lets not bother with that if this is sufficient.
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>

Tested-by: Li Zefan <lizf@...fujitsu.com>

Thanks!

a minor comment

> +		 * lock of the old one. Since these are clearly distrinct

s/distrinct/distinct


BTW, I found another bug in current code:

From: Li Zefan <lizf@...fujitsu.com>
Date: Tue, 10 Feb 2009 10:55:53 +0800
Subject: [PATCH] vfs: add missing unlock in sget()

We should release s->s_umount before calling destroy_super(s).

Signed-off-by: Li Zefan <lizf@...fujitsu.com>
---
 fs/super.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index 61dce00..8bdf981 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -356,8 +356,10 @@ retry:
 				continue;
 			if (!grab_super(old))
 				goto retry;
-			if (s)
+			if (s) {
+				up_write(&s->s_umount);
 				destroy_super(s);
+			}
 			return old;
 		}
 	}
-- 
1.5.4.rc3


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