ceph: fetch cap_gen under spinlock in ceph_add_cap

It's protected by the s_gen_ttl_lock, so we should fetch under it
and ensure that we're using the same generation in both places.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 4615f2501e15..bdfec8978479 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -614,6 +614,7 @@ void ceph_add_cap(struct inode *inode,
         struct ceph_cap *cap;
         int mds = session->s_mds;
         int actual_wanted;
+        u32 gen;
 
         dout("add_cap %p mds%d cap %llx %s seq %d\n", inode,
              session->s_mds, cap_id, ceph_cap_string(issued), seq);
@@ -625,6 +626,10 @@ void ceph_add_cap(struct inode *inode,
         if (fmode >= 0)
                 wanted |= ceph_caps_for_mode(fmode);
 
+        spin_lock(&session->s_gen_ttl_lock);
+        gen = session->s_cap_gen;
+        spin_unlock(&session->s_gen_ttl_lock);
+
         cap = __get_cap_for_mds(ci, mds);
         if (!cap) {
                 cap = *new_cap;
@@ -650,7 +655,7 @@ void ceph_add_cap(struct inode *inode,
                 list_move_tail(&cap->session_caps, &session->s_caps);
                 spin_unlock(&session->s_cap_lock);
 
-                if (cap->cap_gen < session->s_cap_gen)
+                if (cap->cap_gen < gen)
                         cap->issued = cap->implemented = CEPH_CAP_PIN;
 
                 /*
@@ -744,7 +749,7 @@ void ceph_add_cap(struct inode *inode,
         cap->seq = seq;
         cap->issue_seq = seq;
         cap->mseq = mseq;
-        cap->cap_gen = session->s_cap_gen;
+        cap->cap_gen = gen;
 
         if (fmode >= 0)
                 __ceph_get_fmode(ci, fmode);