[PATCH 5/8] eventfs: adding functions to create eventfs files and directories

Ajay Kaher
2023-01-22T17:07:51Z

Adding eventfs_create_file(), eventfs_create_dir()
to create file, dir at runtime as and when requires.

These function will be called either from lookup
of inode_operations or open of file_operations.

Signed-off-by: Ajay Kaher <akaher@vmware.com>
Co-developed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Tested-by: Ching-lin Yu <chinglinyu@google.com>
---
fs/tracefs/event_inode.c | 137 ++++++++++++++++++++++++++++++++++++++++++++++-
fs/tracefs/inode.c | 47 ++++++++++++++++
include/linux/tracefs.h | 6 +++
3 files changed, 189 insertions(+), 1 deletion(-)

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 4d47da0..28866c0 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -21,6 +21,141 @@
#include <linux/kref.h>
#include "internal.h"

+/**
+ * eventfs_create_file - create a file in the tracefs filesystem
+ * @name: a pointer to a string containing the name of the file to create.
+ * @mode: the permission that the file should have.
+ * @parent: a pointer to the parent dentry for this file. This should be a
+ * directory dentry if set. If this parameter is NULL, then the
+ * file will be created in the root of the tracefs filesystem.
+ * @data: a pointer to something that the caller will want to get to later
+ * on. The inode.i_private pointer will point to this value on
+ * the open() call.
+ * @fops: a pointer to a struct file_operations that should be used for
+ * this file.
+ *
+ * This is the basic "create a file" function for tracefs. It allows for a
+ * wide range of flexibility in creating a file.
+ *
+ * This function will return a pointer to a dentry if it succeeds. This
+ * pointer must be passed to the tracefs_remove() function when the file is
+ * to be removed (no automatic cleanup happens if your module is unloaded,
+ * you are responsible here.) If an error occurs, %NULL will be returned.
+ *
+ * If tracefs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+struct dentry *eventfs_create_file(const char *name, umode_t mode,
+ struct dentry *parent, void *data,
+ const struct file_operations *fop,
+ bool anon)
+{
+ struct tracefs_inode *ti;
+ struct dentry *dentry;
+ struct inode *inode;
+
+ if (security_locked_down(LOCKDOWN_TRACEFS))
+ return NULL;
+
+ if (!(mode & S_IFMT))
+ mode |= S_IFREG;
+
+ if (WARN_ON_ONCE(!S_ISREG(mode)))
+ return NULL;
+
+ dentry = eventfs_start_creating(name, parent);
+
+ if (IS_ERR(dentry))
+ return dentry;
+
+ inode = tracefs_get_inode(dentry->d_sb);
+ if (unlikely(!inode))
+ return eventfs_failed_creating(dentry);
+
+ inode->i_mode = mode;
+ inode->i_fop = fop;
+ inode->i_private = data;
+
+ ti = get_tracefs(inode);
+ ti->flags |= TRACEFS_EVENT_INODE;
+
+ if (anon)
+ d_instantiate_anon(dentry, inode);
+ else
+ d_instantiate(dentry, inode);
+
+ fsnotify_create(dentry->d_parent->d_inode, dentry);
+ return eventfs_end_creating(dentry);
+}
+
+/**
+ * eventfs_create_dir - create a dir in the tracefs filesystem
+ * @name: a pointer to a string containing the name of the file to create.
+ * @mode: the permission that the file should have.
+ * @parent: a pointer to the parent dentry for this file. This should be a
+ * directory dentry if set. If this parameter is NULL, then the
+ * file will be created in the root of the tracefs filesystem.
+ * @data: a pointer to something that the caller will want to get to later
+ * on. The inode.i_private pointer will point to this value on
+ * the open() call.
+ * @fop: a pointer to a struct file_operations that should be used for
+ * this dir.
+ * @iop: a pointer to a struct inode_operations that should be used for
+ * this dir.
+ *
+ * This is the basic "create a dir" function for eventfs. It allows for a
+ * wide range of flexibility in creating a dir.
+ *
+ * This function will return a pointer to a dentry if it succeeds. This
+ * pointer must be passed to the tracefs_remove() function when the file is
+ * to be removed (no automatic cleanup happens if your module is unloaded,
+ * you are responsible here.) If an error occurs, %NULL will be returned.
+ *
+ * If tracefs is not enabled in the kernel, the value -%ENODEV will be
+ * returned.
+ */
+struct dentry *eventfs_create_dir(const char *name, umode_t mode,
+ struct dentry *parent, void *data,
+ const struct file_operations *fop,
+ const struct inode_operations *iop,
+ bool anon)
+{
+ struct tracefs_inode *ti;
+ struct dentry *dentry;
+ struct inode *inode;
+
+ if (security_locked_down(LOCKDOWN_TRACEFS))
+ return NULL;
+
+ WARN_ON(!S_ISDIR(mode));
+
+ dentry = eventfs_start_creating(name, parent);
+
+ if (IS_ERR(dentry))
+ return dentry;
+
+ inode = tracefs_get_inode(dentry->d_sb);
+ if (unlikely(!inode))
+ return eventfs_failed_creating(dentry);
+
+ inode->i_mode = mode;
+ inode->i_op = iop;
+ inode->i_fop = fop;
+ inode->i_private = data;
+
+ ti = get_tracefs(inode);
+ ti->flags |= TRACEFS_EVENT_INODE;
+
+ inc_nlink(inode);
+ if (anon)
+ d_instantiate_anon(dentry, inode);
+ else
+ d_instantiate(dentry, inode);
+ inc_nlink(dentry->d_parent->d_inode);
+ fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
+ return eventfs_end_creating(dentry);
+}
+
static const struct file_operations eventfs_file_operations = {
};

@@ -86,9 +221,9 @@ struct dentry *eventfs_create_events_dir(const char *name, struct dentry *parent
*/
struct eventfs_file *eventfs_add_subsystem_dir(const char *name, struct dentry *parent)
{
- struct eventfs_file *ef;
struct tracefs_inode *ti_parent;
struct eventfs_inode *ei_parent;
+ struct eventfs_file *ef;

if (!parent)
return ERR_PTR(-EINVAL);
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index 015b7b8..6d950d1 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -451,6 +451,53 @@ struct dentry *tracefs_end_creating(struct dentry *dentry)
return dentry;
}

+struct dentry *eventfs_start_creating(const char *name, struct dentry *parent)
+{
+ struct dentry *dentry;
+ int error;
+
+ error = simple_pin_fs(&trace_fs_type, &tracefs_mount,
+ &tracefs_mount_count);
+ if (error)
+ return ERR_PTR(error);
+
+ /*
+ * If the parent is not specified, we create it in the root.
+ * We need the root dentry to do this, which is in the super
+ * block. A pointer to that is in the struct vfsmount that we
+ * have around.
+ */
+ if (!parent)
+ parent = tracefs_mount->mnt_root;
+
+ if (unlikely(IS_DEADDIR(parent->d_inode)))
+ dentry = ERR_PTR(-ENOENT);
+ else
+ dentry = lookup_one_len(name, parent, strlen(name));
+
+ if (!IS_ERR(dentry) && dentry->d_inode) {
+ dput(dentry);
+ dentry = ERR_PTR(-EEXIST);
+ }
+
+ if (IS_ERR(dentry))
+ simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+
+ return dentry;
+}
+
+struct dentry *eventfs_failed_creating(struct dentry *dentry)
+{
+ dput(dentry);
+ simple_release_fs(&tracefs_mount, &tracefs_mount_count);
+ return NULL;
+}
+
+struct dentry *eventfs_end_creating(struct dentry *dentry)
+{
+ return dentry;
+}
+
/**
* tracefs_create_file - create a file in the tracefs filesystem
* @name: a pointer to a string containing the name of the file to create.
diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h
index b02cbba..52201f3 100644
--- a/include/linux/tracefs.h
+++ b/include/linux/tracefs.h
@@ -38,6 +38,12 @@ struct eventfs_file {
bool created;
};

+struct dentry *eventfs_start_creating(const char *name, struct dentry *parent);
+
+struct dentry *eventfs_failed_creating(struct dentry *dentry);
+
+struct dentry *eventfs_end_creating(struct dentry *dentry);
+
struct dentry *eventfs_create_events_dir(const char *name,
struct dentry *parent);

--
2.7.4