[PATCH 6/8] ceph: use READ_ONCE to access d_parent in RCU critical section

From: Yan, Zheng
Date: Thu May 23 2019 - 04:09:54 EST


Signed-off-by: "Yan, Zheng" <zyan@xxxxxxxxxx>
---
fs/ceph/mds_client.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 60e8ddbdfdc5..870754e9d572 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -913,7 +913,7 @@ static int __choose_mds(struct ceph_mds_client *mdsc,
struct inode *dir;

rcu_read_lock();
- parent = req->r_dentry->d_parent;
+ parent = READ_ONCE(req->r_dentry->d_parent);
dir = req->r_parent ? : d_inode_rcu(parent);

if (!dir || dir->i_sb != mdsc->fsc->sb) {
@@ -2131,8 +2131,8 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {
dout("build_path path+%d: %p SNAPDIR\n",
pos, temp);
- } else if (stop_on_nosnap && inode && dentry != temp &&
- ceph_snap(inode) == CEPH_NOSNAP) {
+ } else if (stop_on_nosnap && dentry != temp &&
+ inode && ceph_snap(inode) == CEPH_NOSNAP) {
spin_unlock(&temp->d_lock);
pos++; /* get rid of any prepended '/' */
break;
@@ -2145,7 +2145,7 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
memcpy(path + pos, temp->d_name.name, temp->d_name.len);
}
spin_unlock(&temp->d_lock);
- temp = temp->d_parent;
+ temp = READ_ONCE(temp->d_parent);

/* Are we at the root? */
if (IS_ROOT(temp))
--
2.17.2