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 <[email protected]> --- fs/ceph/caps.c | 4 ++-- fs/ceph/dir.c | 14 +++----------- fs/ceph/mds_client.c | 8 +++++--- fs/ceph/mds_client.h | 7 +++++-- 4 files changed, 15 insertions(+), 18 deletions(-) diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index 8b53193..90d789d 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -641,10 +641,10 @@ static int __cap_is_valid(struct ceph_cap *cap) unsigned long ttl; u32 gen; - spin_lock(&cap->session->s_cap_lock); + spin_lock(&cap->session->s_gen_ttl_lock); gen = cap->session->s_cap_gen; ttl = cap->session->s_cap_ttl; - spin_unlock(&cap->session->s_cap_lock); + spin_unlock(&cap->session->s_gen_ttl_lock); if (cap->cap_gen < gen || time_after_eq(jiffies, ttl)) { dout("__cap_is_valid %p cap %p issued %s " diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c index ab2b035..a1a0693 100644 --- a/fs/ceph/dir.c +++ b/fs/ceph/dir.c @@ -971,24 +971,16 @@ static int dentry_lease_is_valid(struct dentry *dentry) struct inode *dir = NULL; u32 seq = 0; -retry: spin_lock(&dentry->d_lock); di = ceph_dentry(dentry); if (di->lease_session) { s = di->lease_session; ceph_get_mds_session(s); - spin_unlock(&dentry->d_lock); - spin_lock(&s->s_cap_lock); - spin_lock(&dentry->d_lock); - if (di->lease_session != s) { - spin_unlock(&s->s_cap_lock); - spin_unlock(&dentry->d_lock); - ceph_put_mds_session(s); - goto retry; - } + + 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) && diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index 23ab6a3..2b0e274 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -398,9 +398,11 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc, s->s_con.peer_name.type = CEPH_ENTITY_TYPE_MDS; s->s_con.peer_name.num = cpu_to_le64(mds); - spin_lock_init(&s->s_cap_lock); + spin_lock_init(&s->s_gen_ttl_lock); s->s_cap_gen = 0; s->s_cap_ttl = 0; + + spin_lock_init(&s->s_cap_lock); s->s_renew_requested = 0; s->s_renew_seq = 0; INIT_LIST_HEAD(&s->s_caps); @@ -2326,10 +2328,10 @@ static void handle_session(struct ceph_mds_session *session, case CEPH_SESSION_STALE: pr_info("mds%d caps went stale, renewing\n", session->s_mds); - spin_lock(&session->s_cap_lock); + spin_lock(&session->s_gen_ttl_lock); session->s_cap_gen++; session->s_cap_ttl = 0; - spin_unlock(&session->s_cap_lock); + spin_unlock(&session->s_gen_ttl_lock); send_renew_caps(mdsc, session); break; diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h index a50ca0e..8c7c04e 100644 --- a/fs/ceph/mds_client.h +++ b/fs/ceph/mds_client.h @@ -117,10 +117,13 @@ struct ceph_mds_session { void *s_authorizer_buf, *s_authorizer_reply_buf; size_t s_authorizer_buf_len, s_authorizer_reply_buf_len; - /* protected by s_cap_lock */ - spinlock_t s_cap_lock; + /* protected by s_gen_ttl_lock */ + spinlock_t s_gen_ttl_lock; u32 s_cap_gen; /* inc each time we get mds stale msg */ unsigned long s_cap_ttl; /* when session caps expire */ + + /* protected by s_cap_lock */ + spinlock_t s_cap_lock; struct list_head s_caps; /* all caps issued by this session */ int s_nr_caps, s_trim_caps; int s_num_cap_releases; -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
