ceph: allow dentry_lease_is_valid to work under RCU walk

Under rcuwalk, we need to take extra care when dereferencing d_parent.
We want to do that once and pass a pointer to dentry_lease_is_valid.

Also, we must ensure that that function can handle the case where we're
racing with d_release. Check whether "di" is NULL under the d_lock, and
just return 0 if so.

Finally, we still need to kick off a renewal job if the lease is getting
close to expiration. If that's the case, then just drop out of rcuwalk
mode since that could block.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Yan, Zheng <zyan@redhat.com>

diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index 904dc67..60dcca1 100644 (file)
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -1133,7 +1133,8 @@ void ceph_invalidate_dentry_lease(struct dentry *dentry)
  * Check if dentry lease is valid.  If not, delete the lease.  Try to
  * renew if the least is more than half up.
  */
-static int dentry_lease_is_valid(struct dentry *dentry)
+static int dentry_lease_is_valid(struct dentry *dentry, unsigned int flags,
+                                struct inode *dir)
 {
        struct ceph_dentry_info *di;
        struct ceph_mds_session *s;
@@ -1141,12 +1142,11 @@ static int dentry_lease_is_valid(struct dentry *dentry)
        u32 gen;
        unsigned long ttl;
        struct ceph_mds_session *session = NULL;
-       struct inode *dir = NULL;
        u32 seq = 0;
 
        spin_lock(&dentry->d_lock);
        di = ceph_dentry(dentry);
-       if (di->lease_session) {
+       if (di && di->lease_session) {
                s = di->lease_session;
                spin_lock(&s->s_gen_ttl_lock);
                gen = s->s_cap_gen;
@@ -1159,12 +1159,19 @@ static int dentry_lease_is_valid(struct dentry *dentry)
                        valid = 1;
                        if (di->lease_renew_after &&
                            time_after(jiffies, di->lease_renew_after)) {
-                               /* we should renew */
-                               dir = d_inode(dentry->d_parent);
-                               session = ceph_get_mds_session(s);
-                               seq = di->lease_seq;
-                               di->lease_renew_after = 0;
-                               di->lease_renew_from = jiffies;
+                               /*
+                                * We should renew. If we're in RCU walk mode
+                                * though, we can't do that so just return
+                                * -ECHILD.
+                                */
+                               if (flags & LOOKUP_RCU) {
+                                       valid = -ECHILD;
+                               } else {
+                                       session = ceph_get_mds_session(s);
+                                       seq = di->lease_seq;
+                                       di->lease_renew_after = 0;
+                                       di->lease_renew_from = jiffies;
+                               }
                        }
                }
        }
@@ -1224,12 +1231,16 @@ static int ceph_d_revalidate(struct dentry *dentry, unsigned int flags)
        } else if (d_really_is_positive(dentry) &&
                   ceph_snap(d_inode(dentry)) == CEPH_SNAPDIR) {
                valid = 1;
-       } else if (dentry_lease_is_valid(dentry) ||
-                  dir_lease_is_valid(dir, dentry)) {
-               if (d_really_is_positive(dentry))
-                       valid = ceph_is_any_caps(d_inode(dentry));
-               else
-                       valid = 1;
+       } else {
+               valid = dentry_lease_is_valid(dentry, flags, dir);
+               if (valid == -ECHILD)
+                       return valid;
+               if (valid || dir_lease_is_valid(dir, dentry)) {
+                       if (d_really_is_positive(dentry))
+                               valid = ceph_is_any_caps(d_inode(dentry));
+                       else
+                               valid = 1;
+               }
        }
 
        if (!valid) {