ceph: fetch cap_gen under spinlock in ceph_add_cap

[ Upstream commit 606d102327a45a49d293557527802ee7fbfd7af1 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index ce0f5658720ab9d06764c1f63dbe3d267ffb336f..8fd5301128106c877f02b34382419ad1208b0aec 100644 (file)
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -645,6 +645,7 @@ 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);
@@ -656,6 +657,10 @@ 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;
@@ -681,7 +686,7 @@ 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;
 
                /*
@@ -775,7 +780,7 @@ 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);