[PATCH v4 19/54] convert tracefs

[Al Viro <viro@zeniv.linux.org.uk>]

A mix of persistent and non-persistent dentries in there.  Strictly
speaking, no need for kill_litter_super() anyway - it pins an internal
mount whenever a persistent dentry is created, so at fs shutdown time
there won't be any to deal with.

However, let's make it explicit - replace d_instantiate() with
d_make_persistent() + dput() (the latter in tracefs_end_creating(),
where it folds with inode_unlock() into simple_done_creating())
for dentries we want persistent and have d_make_discardable() done
either by simple_recursive_removal() (used by tracefs_remove())
or explicitly in eventfs_remove_events_dir().

Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/tracefs/event_inode.c |  4 ++--
 fs/tracefs/inode.c       | 13 ++++++-------
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 93c231601c8e..61cbdafa2411 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -823,7 +823,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
 	 * something not worth much. Keeping directory links at 1
 	 * tells userspace not to trust the link number.
 	 */
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	/* The dentry of the "events" parent does keep track though */
 	inc_nlink(dentry->d_parent->d_inode);
 	fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
@@ -910,5 +910,5 @@ void eventfs_remove_events_dir(struct eventfs_inode *ei)
 	 * and destroyed dynamically.
 	 */
 	d_invalidate(dentry);
-	dput(dentry);
+	d_make_discardable(dentry);
 }
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 0c023941a316..d9d8932a7b9c 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -538,7 +538,7 @@ static struct file_system_type trace_fs_type = {
 	.name =		"tracefs",
 	.init_fs_context = tracefs_init_fs_context,
 	.parameters	= tracefs_param_specs,
-	.kill_sb =	kill_litter_super,
+	.kill_sb =	kill_anon_super,
 };
 MODULE_ALIAS_FS("tracefs");
 
@@ -571,16 +571,15 @@ struct dentry *tracefs_start_creating(const char *name, struct dentry *parent)
 
 struct dentry *tracefs_failed_creating(struct dentry *dentry)
 {
-	inode_unlock(d_inode(dentry->d_parent));
-	dput(dentry);
+	simple_done_creating(dentry);
 	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
 	return NULL;
 }
 
 struct dentry *tracefs_end_creating(struct dentry *dentry)
 {
-	inode_unlock(d_inode(dentry->d_parent));
-	return dentry;
+	simple_done_creating(dentry);
+	return dentry;	// borrowed
 }
 
 /* Find the inode that this will use for default */
@@ -661,7 +660,7 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
 	inode->i_private = data;
 	inode->i_uid = d_inode(dentry->d_parent)->i_uid;
 	inode->i_gid = d_inode(dentry->d_parent)->i_gid;
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	fsnotify_create(d_inode(dentry->d_parent), dentry);
 	return tracefs_end_creating(dentry);
 }
@@ -692,7 +691,7 @@ static struct dentry *__create_dir(const char *name, struct dentry *parent,
 
 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
 	inc_nlink(inode);
-	d_instantiate(dentry, inode);
+	d_make_persistent(dentry, inode);
 	inc_nlink(d_inode(dentry->d_parent));
 	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
 	return tracefs_end_creating(dentry);
-- 
2.47.3