[PATCH AUTOSEL 5.2 12/63] ceph: fetch cap_gen under spinlock in ceph_add_cap

[Sasha Levin]

From: Jeff Layton <jlay...@kernel.org>

[ 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 <jlay...@kernel.org>
Reviewed-by: "Yan, Zheng" <z...@redhat.com>
Signed-off-by: Ilya Dryomov <idryo...@gmail.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 fs/ceph/caps.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 622467e47cde8..07ac2de542eb3 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -644,6 +644,7 @@ 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);
@@ -655,6 +656,10 @@ 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;
@@ -680,7 +685,7 @@ 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;
 
                /*
@@ -774,7 +779,7 @@ 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);
-- 
2.20.1