ceph: do not confuse stale and dead (unreconnected) caps

We were using the cap_gen to track both stale caps (caps that timed out
due to temporarily losing touch with the mds) and dead caps that did not
reconnect after an MDS failure.  Introduce a recon_gen counter to track
reconnections to restarted MDSs and kill dead caps based on that instead.

Rename gen to cap_gen while we're at it to make it more clear which is
which.
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/caps.c

@@ -609,7 +609,8 @@ int ceph_add_cap(struct inode *inode,
 	cap->seq = seq;
 	cap->issue_seq = seq;
 	cap->mseq = mseq;
-	cap->gen = session->s_cap_gen;
+	cap->cap_gen = session->s_cap_gen;
+	cap->recon_gen = session->s_recon_gen;
 
 	if (fmode >= 0)
 		__ceph_get_fmode(ci, fmode);
@@ -626,17 +627,25 @@ int ceph_add_cap(struct inode *inode,
 static int __cap_is_valid(struct ceph_cap *cap)
 {
 	unsigned long ttl;
-	u32 gen;
+	u32 gen, recon_gen;
 
 	spin_lock(&cap->session->s_cap_lock);
 	gen = cap->session->s_cap_gen;
+	recon_gen = cap->session->s_recon_gen;
 	ttl = cap->session->s_cap_ttl;
 	spin_unlock(&cap->session->s_cap_lock);
 
-	if (cap->gen < gen || time_after_eq(jiffies, ttl)) {
+	if (cap->recon_gen != recon_gen) {
+		dout("__cap_is_valid %p cap %p issued %s "
+		     "but DEAD (recon_gen %u vs %u)\n", &cap->ci->vfs_inode,
+		     cap, ceph_cap_string(cap->issued), cap->recon_gen,
+		     recon_gen);
+		return 0;
+	}
+	if (cap->cap_gen < gen || time_after_eq(jiffies, ttl)) {
 		dout("__cap_is_valid %p cap %p issued %s "
 		     "but STALE (gen %u vs %u)\n", &cap->ci->vfs_inode,
-		     cap, ceph_cap_string(cap->issued), cap->gen, gen);
+		     cap, ceph_cap_string(cap->issued), cap->cap_gen, gen);
 		return 0;
 	}
 
@@ -2203,7 +2212,8 @@ static int handle_cap_grant(struct inode *inode, struct ceph_mds_caps *grant,
 	issued = __ceph_caps_issued(ci, &implemented);
 	issued |= implemented | __ceph_caps_dirty(ci);
 
-	cap->gen = session->s_cap_gen;
+	cap->cap_gen = session->s_cap_gen;
+	cap->recon_gen = session->s_recon_gen;
 
 	__check_cap_issue(ci, cap, newcaps);
 

fs/ceph/mds_client.c

@@ -329,6 +329,7 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
 	ceph_con_open(&s->s_con, ceph_mdsmap_get_addr(mdsc->mdsmap, mds));
 
 	spin_lock_init(&s->s_cap_lock);
+	s->s_recon_gen = 0;
 	s->s_cap_gen = 0;
 	s->s_cap_ttl = 0;
 	s->s_renew_requested = 0;
@@ -738,10 +739,11 @@ static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap,
 	struct ceph_mds_session *session = arg;
 
 	spin_lock(&inode->i_lock);
-	if (cap->gen != session->s_cap_gen) {
+	if (cap->recon_gen != session->s_recon_gen) {
 		pr_err("failed reconnect %p %llx.%llx cap %p "
-		       "(gen %d < session %d)\n", inode, ceph_vinop(inode),
-		       cap, cap->gen, session->s_cap_gen);
+		       "(recon_gen %d < session %d)\n", inode,
+		       ceph_vinop(inode), cap,
+		       cap->recon_gen, session->s_recon_gen);
 		__ceph_remove_cap(cap, NULL);
 	}
 	wake_up(&ceph_inode(inode)->i_cap_wq);
@@ -2050,6 +2052,7 @@ static void send_mds_reconnect(struct ceph_mds_client *mdsc, int mds)
 
 		session->s_state = CEPH_MDS_SESSION_RECONNECTING;
 		session->s_seq = 0;
+		session->s_recon_gen++;
 
 		ceph_con_open(&session->s_con,
 			      ceph_mdsmap_get_addr(mdsc->mdsmap, mds));

fs/ceph/mds_client.h

@@ -98,6 +98,8 @@ struct ceph_mds_session {
 	u64               s_seq;      /* incoming msg seq # */
 	struct mutex      s_mutex;    /* serialize session messages */
 
+	int               s_recon_gen; /* inc on reconnect to recovered mds */
+
 	struct ceph_connection s_con;
 
 	/* protected by s_cap_lock */

fs/ceph/super.h

@@ -169,7 +169,9 @@ struct ceph_cap {
 	int issued;       /* latest, from the mds */
 	int implemented;  /* implemented superset of issued (for revocation) */
 	int mds_wanted;
-	u32 seq, issue_seq, mseq, gen;
+	u32 seq, issue_seq, mseq;
+	u32 cap_gen;      /* active/stale cycle */
+	u32 recon_gen;    /* mds restart reconnect cycle */
 	unsigned long last_used;
 	struct list_head caps_item;
 };