Add eventfs_file structure which will hold the properties of the eventfs files and directories.
Add following functions to create the directories in eventfs:
eventfs_create_events_dir() will create the top level "events" directory within the tracefs file system.
eventfs_add_subsystem_dir() creates an eventfs_file descriptor with the given name of the subsystem.
eventfs_add_dir() creates an eventfs_file descriptor with the given name of the directory and attached to a eventfs_file of a subsystem.
Add tracefs_inode structure to hold the inodes, flags and pointers to private data used by eventfs.
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 Reported-by: kernel test robot lkp@intel.com Closes: https://lore.kernel.org/oe-lkp/202305051619.9a469a9a-yujie.liu@intel.com --- fs/tracefs/Makefile | 1 + fs/tracefs/event_inode.c | 211 +++++++++++++++++++++++++++++++++++++++ include/linux/tracefs.h | 11 ++ 3 files changed, 223 insertions(+) create mode 100644 fs/tracefs/event_inode.c
diff --git a/fs/tracefs/Makefile b/fs/tracefs/Makefile index 7c35a282b484..73c56da8e284 100644 --- a/fs/tracefs/Makefile +++ b/fs/tracefs/Makefile @@ -1,5 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only tracefs-objs := inode.o +tracefs-objs += event_inode.o
obj-$(CONFIG_TRACING) += tracefs.o
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c new file mode 100644 index 000000000000..8f334b122e46 --- /dev/null +++ b/fs/tracefs/event_inode.c @@ -0,0 +1,211 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * event_inode.c - part of tracefs, a pseudo file system for activating tracing + * + * Copyright (C) 2020-23 VMware Inc, author: Steven Rostedt (VMware) rostedt@goodmis.org + * Copyright (C) 2020-23 VMware Inc, author: Ajay Kaher akaher@vmware.com + * + * eventfs is used to dynamically create inodes and dentries based on the + * meta data provided by the tracing system. + * + * eventfs stores the meta-data of files/dirs and holds off on creating + * inodes/dentries of the files. When accessed, the eventfs will create the + * inodes/dentries in a just-in-time (JIT) manner. The eventfs will clean up + * and delete the inodes/dentries when they are no longer referenced. + */ +#include <linux/fsnotify.h> +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/workqueue.h> +#include <linux/security.h> +#include <linux/tracefs.h> +#include <linux/kref.h> +#include <linux/delay.h> +#include "internal.h" + +struct eventfs_inode { + struct list_head e_top_files; +}; + +/** + * struct eventfs_file - hold the properties of the eventfs files and + * directories. + * @name: the name of the file or directory to create + * @list: file or directory to be added to parent directory + * @ei: list of files and directories within directory + * @fop: file_operations for file or directory + * @iop: inode_operations for file or directory + * @data: something that the caller will want to get to later on + * @mode: the permission that the file or directory should have + */ +struct eventfs_file { + const char *name; + struct list_head list; + struct eventfs_inode *ei; + const struct file_operations *fop; + const struct inode_operations *iop; + void *data; + umode_t mode; +}; + +static DEFINE_MUTEX(eventfs_mutex); + +static const struct inode_operations eventfs_root_dir_inode_operations = { +}; + +static const struct file_operations eventfs_file_operations = { +}; + +/** + * eventfs_prepare_ef - helper function to prepare eventfs_file + * @name: the name of the file/directory to create. + * @mode: the permission that the file should have. + * @fop: struct file_operations that should be used for this file/directory. + * @iop: struct inode_operations that should be used for this file/directory. + * @data: 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. + * + * This function allocates and fills the eventfs_file structure. + */ +static struct eventfs_file *eventfs_prepare_ef(const char *name, umode_t mode, + const struct file_operations *fop, + const struct inode_operations *iop, + void *data) +{ + struct eventfs_file *ef; + + ef = kzalloc(sizeof(*ef), GFP_KERNEL); + if (!ef) + return ERR_PTR(-ENOMEM); + + ef->name = kstrdup(name, GFP_KERNEL); + if (!ef->name) { + kfree(ef); + return ERR_PTR(-ENOMEM); + } + + if (S_ISDIR(mode)) { + ef->ei = kzalloc(sizeof(*ef->ei), GFP_KERNEL); + if (!ef->ei) { + kfree(ef->name); + kfree(ef); + return ERR_PTR(-ENOMEM); + } + INIT_LIST_HEAD(&ef->ei->e_top_files); + } else { + ef->ei = NULL; + } + + ef->iop = iop; + ef->fop = fop; + ef->mode = mode; + ef->data = data; + return ef; +} + +/** + * eventfs_create_events_dir - create the trace event structure + * @name: the name of the directory to create. + * @parent: parent dentry for this file. This should be a directory dentry + * if set. If this parameter is NULL, then the directory will be + * created in the root of the tracefs filesystem. + * + * This function creates the top of the trace event directory. + */ +struct dentry *eventfs_create_events_dir(const char *name, + struct dentry *parent) +{ + struct dentry *dentry = tracefs_start_creating(name, parent); + struct eventfs_inode *ei; + struct tracefs_inode *ti; + struct inode *inode; + + if (IS_ERR(dentry)) + return dentry; + + ei = kzalloc(sizeof(*ei), GFP_KERNEL); + if (!ei) + return ERR_PTR(-ENOMEM); + inode = tracefs_get_inode(dentry->d_sb); + if (unlikely(!inode)) { + kfree(ei); + tracefs_failed_creating(dentry); + return ERR_PTR(-ENOMEM); + } + + INIT_LIST_HEAD(&ei->e_top_files); + + ti = get_tracefs(inode); + ti->flags |= TRACEFS_EVENT_INODE; + ti->private = ei; + + inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO; + inode->i_op = &eventfs_root_dir_inode_operations; + inode->i_fop = &eventfs_file_operations; + + /* directory inodes start off with i_nlink == 2 (for "." entry) */ + inc_nlink(inode); + d_instantiate(dentry, inode); + inc_nlink(dentry->d_parent->d_inode); + fsnotify_mkdir(dentry->d_parent->d_inode, dentry); + return tracefs_end_creating(dentry); +} + +/** + * eventfs_add_subsystem_dir - add eventfs subsystem_dir to list to create later + * @name: the name of the file to create. + * @parent: parent dentry for this dir. + * + * This function adds eventfs subsystem dir to list. + * And all these dirs are created on the fly when they are looked up, + * and the dentry and inodes will be removed when they are done. + */ +struct eventfs_file *eventfs_add_subsystem_dir(const char *name, + struct dentry *parent) +{ + struct tracefs_inode *ti_parent; + struct eventfs_inode *ei_parent; + struct eventfs_file *ef; + + if (!parent) + return ERR_PTR(-EINVAL); + + ti_parent = get_tracefs(parent->d_inode); + ei_parent = ti_parent->private; + + ef = eventfs_prepare_ef(name, S_IFDIR, NULL, NULL, NULL); + if (IS_ERR(ef)) + return ef; + + mutex_lock(&eventfs_mutex); + list_add_tail(&ef->list, &ei_parent->e_top_files); + mutex_unlock(&eventfs_mutex); + return ef; +} + +/** + * eventfs_add_dir - add eventfs dir to list to create later + * @name: the name of the file to create. + * @ef_parent: parent eventfs_file for this dir. + * + * This function adds eventfs dir to list. + * And all these dirs are created on the fly when they are looked up, + * and the dentry and inodes will be removed when they are done. + */ +struct eventfs_file *eventfs_add_dir(const char *name, + struct eventfs_file *ef_parent) +{ + struct eventfs_file *ef; + + if (!ef_parent) + return ERR_PTR(-EINVAL); + + ef = eventfs_prepare_ef(name, S_IFDIR, NULL, NULL, NULL); + if (IS_ERR(ef)) + return ef; + + mutex_lock(&eventfs_mutex); + list_add_tail(&ef->list, &ef_parent->ei->e_top_files); + mutex_unlock(&eventfs_mutex); + return ef; +} diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h index 99912445974c..432e5e6f7901 100644 --- a/include/linux/tracefs.h +++ b/include/linux/tracefs.h @@ -21,6 +21,17 @@ struct file_operations;
#ifdef CONFIG_TRACING
+struct eventfs_file; + +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 *eventfs_add_dir(const char *name, + struct eventfs_file *ef_parent); + struct dentry *tracefs_create_file(const char *name, umode_t mode, struct dentry *parent, void *data, const struct file_operations *fops);