fs/tracefs/inode.c | 147 ++++++++++-------------------------------------------
 1 file changed, 26 insertions(+), 121 deletions(-)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index bc86ffdb103b..5bc9e1a23a31 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -183,87 +183,6 @@ struct tracefs_fs_info {
 	struct tracefs_mount_opts mount_opts;
 };
 
-static void change_gid(struct dentry *dentry, kgid_t gid)
-{
-	if (!dentry->d_inode)
-		return;
-	dentry->d_inode->i_gid = gid;
-}
-
-/*
- * Taken from d_walk, but without he need for handling renames.
- * Nothing can be renamed while walking the list, as tracefs
- * does not support renames. This is only called when mounting
- * or remounting the file system, to set all the files to
- * the given gid.
- */
-static void set_gid(struct dentry *parent, kgid_t gid)
-{
-	struct dentry *this_parent;
-	struct list_head *next;
-
-	this_parent = parent;
-	spin_lock(&this_parent->d_lock);
-
-	change_gid(this_parent, gid);
-repeat:
-	next = this_parent->d_subdirs.next;
-resume:
-	while (next != &this_parent->d_subdirs) {
-		struct tracefs_inode *ti;
-		struct list_head *tmp = next;
-		struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
-		next = tmp->next;
-
-		/* Note, getdents() can add a cursor dentry with no inode */
-		if (!dentry->d_inode)
-			continue;
-
-		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
-
-		change_gid(dentry, gid);
-
-		/* If this is the events directory, update that too */
-		ti = get_tracefs(dentry->d_inode);
-		if (ti && (ti->flags & TRACEFS_EVENT_INODE))
-			eventfs_update_gid(dentry, gid);
-
-		if (!list_empty(&dentry->d_subdirs)) {
-			spin_unlock(&this_parent->d_lock);
-			spin_release(&dentry->d_lock.dep_map, _RET_IP_);
-			this_parent = dentry;
-			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
-			goto repeat;
-		}
-		spin_unlock(&dentry->d_lock);
-	}
-	/*
-	 * All done at this level ... ascend and resume the search.
-	 */
-	rcu_read_lock();
-ascend:
-	if (this_parent != parent) {
-		struct dentry *child = this_parent;
-		this_parent = child->d_parent;
-
-		spin_unlock(&child->d_lock);
-		spin_lock(&this_parent->d_lock);
-
-		/* go into the first sibling still alive */
-		do {
-			next = child->d_child.next;
-			if (next == &this_parent->d_subdirs)
-				goto ascend;
-			child = list_entry(next, struct dentry, d_child);
-		} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
-		rcu_read_unlock();
-		goto resume;
-	}
-	rcu_read_unlock();
-	spin_unlock(&this_parent->d_lock);
-	return;
-}
-
 static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
 {
 	substring_t args[MAX_OPT_ARGS];
@@ -315,49 +234,12 @@ static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts)
 	return 0;
 }
 
-static int tracefs_apply_options(struct super_block *sb, bool remount)
-{
-	struct tracefs_fs_info *fsi = sb->s_fs_info;
-	struct inode *inode = d_inode(sb->s_root);
-	struct tracefs_mount_opts *opts = &fsi->mount_opts;
-	umode_t tmp_mode;
-
-	/*
-	 * On remount, only reset mode/uid/gid if they were provided as mount
-	 * options.
-	 */
-
-	if (!remount || opts->opts & BIT(Opt_mode)) {
-		tmp_mode = READ_ONCE(inode->i_mode) & ~S_IALLUGO;
-		tmp_mode |= opts->mode;
-		WRITE_ONCE(inode->i_mode, tmp_mode);
-	}
-
-	if (!remount || opts->opts & BIT(Opt_uid))
-		inode->i_uid = opts->uid;
-
-	if (!remount || opts->opts & BIT(Opt_gid)) {
-		/* Set all the group ids to the mount option */
-		set_gid(sb->s_root, opts->gid);
-	}
-
-	return 0;
-}
-
 static int tracefs_remount(struct super_block *sb, int *flags, char *data)
 {
-	int err;
 	struct tracefs_fs_info *fsi = sb->s_fs_info;
 
 	sync_filesystem(sb);
-	err = tracefs_parse_options(data, &fsi->mount_opts);
-	if (err)
-		goto fail;
-
-	tracefs_apply_options(sb, true);
-
-fail:
-	return err;
+	return tracefs_parse_options(data, &fsi->mount_opts);
 }
 
 static int tracefs_show_options(struct seq_file *m, struct dentry *root)
@@ -399,8 +281,33 @@ static void tracefs_dentry_iput(struct dentry *dentry, struct inode *inode)
 	iput(inode);
 }
 
+static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags)
+{
+	struct tracefs_fs_info *fsi = dentry->d_sb->s_fs_info;
+	struct tracefs_mount_opts *opts = &fsi->mount_opts;
+	struct inode *inode;
+
+	rcu_read_lock();
+	inode = d_inode_rcu(dentry);
+	if (inode) {
+		if (opts->opts & BIT(Opt_mode)) {
+			umode_t tmp_mode;
+			tmp_mode = READ_ONCE(inode->i_mode) & ~S_IALLUGO;
+			tmp_mode |= opts->mode;
+			WRITE_ONCE(inode->i_mode, tmp_mode);
+		}
+		if (opts->opts & BIT(Opt_uid))
+			inode->i_uid = opts->uid;
+		if (opts->opts & BIT(Opt_gid))
+			inode->i_gid = opts->gid;
+	}
+	rcu_read_unlock();
+	return 0;
+}
+
 static const struct dentry_operations tracefs_dentry_operations = {
 	.d_iput = tracefs_dentry_iput,
+	.d_revalidate = tracefs_d_revalidate,
 };
 
 static int trace_fill_super(struct super_block *sb, void *data, int silent)
@@ -427,8 +334,6 @@ static int trace_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_op = &tracefs_super_operations;
 	sb->s_d_op = &tracefs_dentry_operations;
 
-	tracefs_apply_options(sb, false);
-
 	return 0;
 
 fail: