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>

4 files changed, 26 insertions, 9 deletions

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 8b863dbec70c..775e6f6fc970 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -609,7 +609,8 @@ retry:
         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 @@ retry:
 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 @@ restart:
         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);
 
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 210cb6623ea2..828417ae16f9 100644
--- a/fs/ceph/mds_client.c
+++ b/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));
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index f566e9c84295..c0846b1c482b 100644
--- a/fs/ceph/mds_client.h
+++ b/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 */
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 05947b96c524..25793559a2e5 100644
--- a/fs/ceph/super.h
+++ b/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;
 };