linux-kernel - [PATCH 6/8] ceph: use READ_ONCE to access d

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Date:   Thu, 23 May 2019 16:06:44 +0800
From:   "Yan, Zheng" <zyan@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     idryomov@...hat.com, jlayton@...hat.com
Subject: [PATCH 6/8] ceph: use READ_ONCE to access d_parent in RCU critical section

Signed-off-by: "Yan, Zheng" <zyan@...hat.com>
---
 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