From d8fb02abdc39f92a1066313e2b17047876afa8f9 Mon Sep 17 00:00:00 2001 From: Alex Elder Date: Thu, 12 Jan 2012 17:48:10 -0800 Subject: 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 Reviewed-by: Sage Weil --- fs/ceph/dir.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/ceph/dir.c') diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c index 98954003a8d..63c52f33361 100644 --- a/fs/ceph/dir.c +++ b/fs/ceph/dir.c @@ -975,10 +975,10 @@ static int dentry_lease_is_valid(struct dentry *dentry) di = ceph_dentry(dentry); if (di && di->lease_session) { s = di->lease_session; - spin_lock(&s->s_cap_lock); + spin_lock(&s->s_gen_ttl_lock); gen = s->s_cap_gen; ttl = s->s_cap_ttl; - spin_unlock(&s->s_cap_lock); + spin_unlock(&s->s_gen_ttl_lock); if (di->lease_gen == gen && time_before(jiffies, dentry->d_time) && -- cgit v1.2.3