Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs fixes from Al Viro:
"double iput() on failure exit in lustre, racy removal of spliced
dentries from ->s_anon in __d_materialise_dentry() plus a bunch of
assorted RCU pathwalk fixes"

The RCU pathwalk fixes end up fixing a couple of cases where we
incorrectly dropped out of RCU walking, due to incorrect initialization
and testing of the sequence locks in some corner cases. Since dropping
out of RCU walk mode forces the slow locked accesses, those corner cases
slowed down quite dramatically.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
be careful with nd->inode in path_init() and follow_dotdot_rcu()
don't bugger nd->seq on set_root_rcu() from follow_dotdot_rcu()
fix bogus read_seqretry() checks introduced in b37199e
move the call of __d_drop(anon) into __d_materialise_unique(dentry, anon)
[fix] lustre: d_make_root() does iput() on dentry allocation failure

drivers/staging/lustre/lustre/llite/llite_lib.c

···
 	if (sb->s_root == NULL) {
 		CERROR("%s: can't make root dentry\n",
 			ll_get_fsname(sb, NULL, 0));
-		GOTO(out_root, err = -ENOMEM);
+		GOTO(out_lock_cn_cb, err = -ENOMEM);
 	}
 
 	sbi->ll_sdev_orig = sb->s_dev;

fs/dcache.c

···
 	dentry->d_parent = dentry;
 	list_del_init(&dentry->d_u.d_child);
 	anon->d_parent = dparent;
+	if (likely(!d_unhashed(anon))) {
+		hlist_bl_lock(&anon->d_sb->s_anon);
+		__hlist_bl_del(&anon->d_hash);
+		anon->d_hash.pprev = NULL;
+		hlist_bl_unlock(&anon->d_sb->s_anon);
+	}
 	list_move(&anon->d_u.d_child, &dparent->d_subdirs);
 
 	write_seqcount_end(&dentry->d_seq);
···
 			write_seqlock(&rename_lock);
 			__d_materialise_dentry(dentry, new);
 			write_sequnlock(&rename_lock);
-			__d_drop(new);
 			_d_rehash(new);
 			spin_unlock(&new->d_lock);
 			spin_unlock(&inode->i_lock);
···
 				 * could splice into our tree? */
 				__d_materialise_dentry(dentry, alias);
 				write_sequnlock(&rename_lock);
-				__d_drop(alias);
 				goto found;
 			} else {
 				/* Nope, but we must(!) avoid directory

fs/namei.c

···
 
 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)
···
 			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);
···
 		 */
 		*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 &&
···
 			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;
···
 		}
 		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)) {
···
 			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:
···
 
 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;
···
 	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);
···
 	}
 
 	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)