1 files changed, 32 insertions, 20 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 2be5120b81b..215e44254c5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -644,24 +644,22 @@ static int complete_walk(struct nameidata *nd)
 
 static __always_inline void set_root(struct nameidata *nd)
 {
-	if (!nd->root.mnt)
-		get_fs_root(current->fs, &nd->root);
+	get_fs_root(current->fs, &nd->root);
 }
 
 static int link_path_walk(const char *, struct nameidata *);
 
-static __always_inline void set_root_rcu(struct nameidata *nd)
+static __always_inline unsigned set_root_rcu(struct nameidata *nd)
 {
-	if (!nd->root.mnt) {
-		struct fs_struct *fs = current->fs;
-		unsigned seq;
+	struct fs_struct *fs = current->fs;
+	unsigned seq, res;
 
-		do {
-			seq = read_seqcount_begin(&fs->seq);
-			nd->root = fs->root;
-			nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
-		} while (read_seqcount_retry(&fs->seq, seq));
-	}
+	do {
+		seq = read_seqcount_begin(&fs->seq);
+		nd->root = fs->root;
+		res = __read_seqcount_begin(&nd->root.dentry->d_seq);
+	} while (read_seqcount_retry(&fs->seq, seq));
+	return res;
 }
 
 static void path_put_conditional(struct path *path, struct nameidata *nd)
@@ -861,7 +859,8 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
 			return PTR_ERR(s);
 		}
 		if (*s == '/') {
-			set_root(nd);
+			if (!nd->root.mnt)
+				set_root(nd);
 			path_put(&nd->path);
 			nd->path = nd->root;
 			path_get(&nd->root);
@@ -1138,13 +1137,15 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
 		 */
 		*inode = path->dentry->d_inode;
 	}
-	return read_seqretry(&mount_lock, nd->m_seq) &&
+	return !read_seqretry(&mount_lock, nd->m_seq) &&
 		!(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
 }
 
 static int follow_dotdot_rcu(struct nameidata *nd)
 {
-	set_root_rcu(nd);
+	struct inode *inode = nd->inode;
+	if (!nd->root.mnt)
+		set_root_rcu(nd);
 
 	while (1) {
 		if (nd->path.dentry == nd->root.dentry &&
@@ -1156,6 +1157,7 @@ static int follow_dotdot_rcu(struct nameidata *nd)
 			struct dentry *parent = old->d_parent;
 			unsigned seq;
 
+			inode = parent->d_inode;
 			seq = read_seqcount_begin(&parent->d_seq);
 			if (read_seqcount_retry(&old->d_seq, nd->seq))
 				goto failed;
@@ -1165,6 +1167,7 @@ static int follow_dotdot_rcu(struct nameidata *nd)
 		}
 		if (!follow_up_rcu(&nd->path))
 			break;
+		inode = nd->path.dentry->d_inode;
 		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
 	}
 	while (d_mountpoint(nd->path.dentry)) {
@@ -1174,11 +1177,12 @@ static int follow_dotdot_rcu(struct nameidata *nd)
 			break;
 		nd->path.mnt = &mounted->mnt;
 		nd->path.dentry = mounted->mnt.mnt_root;
+		inode = nd->path.dentry->d_inode;
 		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
-		if (!read_seqretry(&mount_lock, nd->m_seq))
+		if (read_seqretry(&mount_lock, nd->m_seq))
 			goto failed;
 	}
-	nd->inode = nd->path.dentry->d_inode;
+	nd->inode = inode;
 	return 0;
 
 failed:
@@ -1257,7 +1261,8 @@ static void follow_mount(struct path *path)
 
 static void follow_dotdot(struct nameidata *nd)
 {
-	set_root(nd);
+	if (!nd->root.mnt)
+		set_root(nd);
 
 	while(1) {
 		struct dentry *old = nd->path.dentry;
@@ -1853,7 +1858,7 @@ static int path_init(int dfd, const char *name, unsigned int flags,
 	if (*name=='/') {
 		if (flags & LOOKUP_RCU) {
 			rcu_read_lock();
-			set_root_rcu(nd);
+			nd->seq = set_root_rcu(nd);
 		} else {
 			set_root(nd);
 			path_get(&nd->root);
@@ -1904,7 +1909,14 @@ static int path_init(int dfd, const char *name, unsigned int flags,
 	}
 
 	nd->inode = nd->path.dentry->d_inode;
-	return 0;
+	if (!(flags & LOOKUP_RCU))
+		return 0;
+	if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq)))
+		return 0;
+	if (!(nd->flags & LOOKUP_ROOT))
+		nd->root.mnt = NULL;
+	rcu_read_unlock();
+	return -ECHILD;
 }
 
 static inline int lookup_last(struct nameidata *nd, struct path *path)