[for-next][PATCH 02/11] eventfs: Create eventfs_root_inode to store dentry

Steven Rostedt
2024-02-21T14:06:40Z

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Only the root "events" directory stores a dentry. There's no reason to
hold a dentry pointer for every eventfs_inode as it is never set except
for the root "events" eventfs_inode.

Create a eventfs_root_inode structure that holds the events_dir dentry.
The "events" eventfs_inode *is* special, let it have its own descriptor.

Link: https://lore.kernel.org/linux-trace-kernel/20240201161617.658992558@goodmis.org

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Ajay Kaher <ajay.kaher@broadcom.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
fs/tracefs/event_inode.c | 65 +++++++++++++++++++++++++++++++++-------
fs/tracefs/internal.h | 2 --
2 files changed, 55 insertions(+), 12 deletions(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 9d9c7dc3114b..dc067eeb6387 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -35,6 +35,17 @@ static DEFINE_MUTEX(eventfs_mutex);
/* Choose something "unique" ;-) */
#define EVENTFS_FILE_INODE_INO 0x12c4e37

+struct eventfs_root_inode {
+ struct eventfs_inode ei;
+ struct dentry *events_dir;
+};
+
+static struct eventfs_root_inode *get_root_inode(struct eventfs_inode *ei)
+{
+ WARN_ON_ONCE(!ei->is_events);
+ return container_of(ei, struct eventfs_root_inode, ei);
+}
+
/* Just try to make something consistent and unique */
static int eventfs_dir_ino(struct eventfs_inode *ei)
{
@@ -73,12 +84,18 @@ enum {
static void release_ei(struct kref *ref)
{
struct eventfs_inode *ei = container_of(ref, struct eventfs_inode, kref);
+ struct eventfs_root_inode *rei;

WARN_ON_ONCE(!ei->is_freed);

kfree(ei->entry_attrs);
kfree_const(ei->name);
- kfree_rcu(ei, rcu);
+ if (ei->is_events) {
+ rei = get_root_inode(ei);
+ kfree_rcu(rei, ei.rcu);
+ } else {
+ kfree_rcu(ei, rcu);
+ }
}

static inline void put_ei(struct eventfs_inode *ei)
@@ -408,19 +425,43 @@ static struct dentry *lookup_dir_entry(struct dentry *dentry,
return NULL;
}

+static inline struct eventfs_inode *init_ei(struct eventfs_inode *ei, const char *name)
+{
+ ei->name = kstrdup_const(name, GFP_KERNEL);
+ if (!ei->name)
+ return NULL;
+ kref_init(&ei->kref);
+ return ei;
+}
+
static inline struct eventfs_inode *alloc_ei(const char *name)
{
struct eventfs_inode *ei = kzalloc(sizeof(*ei), GFP_KERNEL);
+ struct eventfs_inode *result;

if (!ei)
return NULL;

- ei->name = kstrdup_const(name, GFP_KERNEL);
- if (!ei->name) {
+ result = init_ei(ei, name);
+ if (!result)
kfree(ei);
+
+ return result;
+}
+
+static inline struct eventfs_inode *alloc_root_ei(const char *name)
+{
+ struct eventfs_root_inode *rei = kzalloc(sizeof(*rei), GFP_KERNEL);
+ struct eventfs_inode *ei;
+
+ if (!rei)
return NULL;
- }
- kref_init(&ei->kref);
+
+ rei->ei.is_events = 1;
+ ei = init_ei(&rei->ei, name);
+ if (!ei)
+ kfree(rei);
+
return ei;
}

@@ -710,6 +751,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
int size, void *data)
{
struct dentry *dentry = tracefs_start_creating(name, parent);
+ struct eventfs_root_inode *rei;
struct eventfs_inode *ei;
struct tracefs_inode *ti;
struct inode *inode;
@@ -722,7 +764,7 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
if (IS_ERR(dentry))
return ERR_CAST(dentry);

- ei = alloc_ei(name);
+ ei = alloc_root_ei(name);
if (!ei)
goto fail;

@@ -731,10 +773,11 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
goto fail;

// Note: we have a ref to the dentry from tracefs_start_creating()
- ei->events_dir = dentry;
+ rei = get_root_inode(ei);
+ rei->events_dir = dentry;
+
ei->entries = entries;
ei->nr_entries = size;
- ei->is_events = 1;
ei->data = data;

/* Save the ownership of this directory */
@@ -845,13 +888,15 @@ void eventfs_remove_dir(struct eventfs_inode *ei)
*/
void eventfs_remove_events_dir(struct eventfs_inode *ei)
{
+ struct eventfs_root_inode *rei;
struct dentry *dentry;

- dentry = ei->events_dir;
+ rei = get_root_inode(ei);
+ dentry = rei->events_dir;
if (!dentry)
return;

- ei->events_dir = NULL;
+ rei->events_dir = NULL;
eventfs_remove_dir(ei);

/*
diff --git a/fs/tracefs/internal.h b/fs/tracefs/internal.h
index beb3dcd0e434..15c26f9aaad4 100644
--- a/fs/tracefs/internal.h
+++ b/fs/tracefs/internal.h
@@ -36,7 +36,6 @@ struct eventfs_attr {
* @children: link list into the child eventfs_inode
* @entries: the array of entries representing the files in the directory
* @name: the name of the directory to create
- * @events_dir: the dentry of the events directory
* @entry_attrs: Saved mode and ownership of the @d_children
* @data: The private data to pass to the callbacks
* @attr: Saved mode and ownership of eventfs_inode itself
@@ -54,7 +53,6 @@ struct eventfs_inode {
struct list_head children;
const struct eventfs_entry *entries;
const char *name;
- struct dentry *events_dir;
struct eventfs_attr *entry_attrs;
void *data;
struct eventfs_attr attr;
--
2.43.0