From: Alex Elder <elder@dreamhost.com>
Date: Fri, 13 Jan 2012 01:48:10 +0000 (-0800)
Subject: ceph: create a new session lock to avoid lock inversion
X-Git-Tag: v3.3-rc3~30^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d8fb02abdc39f92a1066313e2b17047876afa8f9;p=pandora-kernel.git

ceph: create a new session lock to avoid lock inversion

Lockdep was reporting a possible circular lock dependency in
dentry_lease_is_valid().  That function needs to sample the
session's s_cap_gen and and s_cap_ttl fields coherently, but needs
to do so while holding a dentry lock.  The s_cap_lock field was
being used to protect the two fields, but that can't be taken while
holding a lock on a dentry within the session.

In most cases, the s_cap_gen and s_cap_ttl fields only get operated
on separately.  But in three cases they need to be updated together.
Implement a new lock to protect the spots updating both fields
atomically is required.

Signed-off-by: Alex Elder <elder@dreamhost.com>
Reviewed-by: Sage Weil <sage@newdream.net>
---

Reading git-diff-tree failed