Adding eventfs_file structure which will hold properties of file or dir. Adding following functions to add dir in eventfs: eventfs_create_events_dir() directly creates events dir with-in tracing folder. eventfs_add_subsystem_dir() adds the information of subsystem_dir to eventfs and dynamically creates subsystem_dir as and when requires. eventfs_add_dir() adds the information of dir (which is with-in subsystem_dir) to eventfs and dynamically creates these dir as and when requires. Signed-off-by: Ajay Kaher <akaher@xxxxxxxxxx> Co-developed-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Tested-by: Ching-lin Yu <chinglinyu@xxxxxxxxxx> Reported-by: kernel test robot <lkp@xxxxxxxxx> Link: https://lore.kernel.org/oe-lkp/202305051619.9a469a9a-yujie.liu@xxxxxxxxx --- fs/tracefs/Makefile | 1 + fs/tracefs/event_inode.c | 272 +++++++++++++++++++++++++++++++++++++++ include/linux/tracefs.h | 29 +++++ kernel/trace/trace.h | 1 + 4 files changed, 303 insertions(+) create mode 100644 fs/tracefs/event_inode.c diff --git a/fs/tracefs/Makefile b/fs/tracefs/Makefile index 7c35a282b..73c56da8e 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 000000000..a48ce23c0 --- /dev/null +++ b/fs/tracefs/event_inode.c @@ -0,0 +1,272 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * event_inode.c - part of tracefs, a pseudo file system for activating tracing + * + * Copyright (C) 2020-22 VMware Inc, author: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> + * Copyright (C) 2020-22 VMware Inc, author: Ajay Kaher <akaher@xxxxxxxxxx> + * + * eventfs is used to show trace events with one set of dentries + * + * eventfs stores meta-data of files/dirs and skip to create object of + * inodes/dentries. As and when requires, eventfs will create the + * inodes/dentries for only required files/directories. Also eventfs + * would delete the inodes/dentries once no more requires but preserve + * the meta data. + */ +#include <linux/fsnotify.h> +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/security.h> +#include <linux/tracefs.h> +#include <linux/kref.h> +#include <linux/delay.h> +#include "internal.h" + +/** + * eventfs_dentry_to_rwsem - Return corresponding eventfs_rwsem + * @dentry: a pointer to dentry + * + * helper function to return crossponding eventfs_rwsem for given dentry + */ +static struct rw_semaphore *eventfs_dentry_to_rwsem(struct dentry *dentry) +{ + if (S_ISDIR(dentry->d_inode->i_mode)) + return (struct rw_semaphore *)dentry->d_inode->i_private; + else + return (struct rw_semaphore *)dentry->d_parent->d_inode->i_private; +} + +/** + * eventfs_down_read - acquire read lock function + * @eventfs_rwsem: a pointer to rw_semaphore + * + * helper function to perform read lock. Nested locking requires because + * lookup(), release() requires read lock, these could be called directly + * or from open(), remove() which already hold the read/write lock. + */ +static void eventfs_down_read(struct rw_semaphore *eventfs_rwsem) +{ + down_read_nested(eventfs_rwsem, SINGLE_DEPTH_NESTING); +} + +/** + * eventfs_up_read - release read lock function + * @eventfs_rwsem: a pointer to rw_semaphore + * + * helper function to release eventfs_rwsem lock if locked + */ +static void eventfs_up_read(struct rw_semaphore *eventfs_rwsem) +{ + up_read(eventfs_rwsem); +} + +/** + * eventfs_down_write - acquire write lock function + * @eventfs_rwsem: a pointer to rw_semaphore + * + * helper function to perform write lock on eventfs_rwsem + */ +static void eventfs_down_write(struct rw_semaphore *eventfs_rwsem) +{ + while (!down_write_trylock(eventfs_rwsem)) + msleep(10); +} + +/** + * eventfs_up_write - release write lock function + * @eventfs_rwsem: a pointer to rw_semaphore + * + * helper function to perform write lock on eventfs_rwsem + */ +static void eventfs_up_write(struct rw_semaphore *eventfs_rwsem) +{ + up_write(eventfs_rwsem); +} + +static const struct file_operations eventfs_file_operations = { +}; + +static const struct inode_operations eventfs_root_dir_inode_operations = { +}; + +/** + * eventfs_prepare_ef - helper function to prepare eventfs_file + * @name: a pointer to a string containing the name of the file/directory + * to create. + * @mode: the permission that the file should have. + * @fop: a pointer to a struct file_operations that should be used for + * this file/directory. + * @iop: a pointer to a struct inode_operations that should be used for + * this file/directory. + * @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. + * + * This function allocate the fill 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; + ef->dentry = NULL; + ef->d_parent = NULL; + ef->created = false; + return ef; +} + +/** + * eventfs_create_events_dir - create the trace event structure + * @name: a pointer to a string containing the name of the directory to + * create. + * @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 + * directory will be created in the root of the tracefs filesystem. + * @eventfs_rwsem: a pointer to rw_semaphore + * + * This function creates the top of the trace event directory. + */ +struct dentry *eventfs_create_events_dir(const char *name, + struct dentry *parent, + struct rw_semaphore *eventfs_rwsem) +{ + 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_rwsem(eventfs_rwsem); + 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; + inode->i_private = eventfs_rwsem; + + /* 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: a pointer to a string containing the name of the file to create. + * @parent: a pointer to the parent dentry for this dir. + * @eventfs_rwsem: a pointer to rw_semaphore + * + * 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 rw_semaphore *eventfs_rwsem) +{ + 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 | S_IRWXU | S_IRUGO | S_IXUGO, + &eventfs_file_operations, + &eventfs_root_dir_inode_operations, + (void *) eventfs_rwsem); + + if (IS_ERR(ef)) + return ef; + + eventfs_down_write(eventfs_rwsem); + list_add_tail(&ef->list, &ei_parent->e_top_files); + ef->d_parent = parent; + eventfs_up_write(eventfs_rwsem); + return ef; +} + +/** + * eventfs_add_dir - add eventfs dir to list to create later + * @name: a pointer to a string containing the name of the file to create. + * @ef_parent: a pointer to the parent eventfs_file for this dir. + * @eventfs_rwsem: a pointer to rw_semaphore + * + * 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 rw_semaphore *eventfs_rwsem) +{ + struct eventfs_file *ef; + + if (!ef_parent) + return ERR_PTR(-EINVAL); + + ef = eventfs_prepare_ef(name, + S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO, + &eventfs_file_operations, + &eventfs_root_dir_inode_operations, + (void *) eventfs_rwsem); + + if (IS_ERR(ef)) + return ef; + + eventfs_down_write(eventfs_rwsem); + list_add_tail(&ef->list, &ef_parent->ei->e_top_files); + ef->d_parent = ef_parent->dentry; + eventfs_up_write(eventfs_rwsem); + return ef; +} diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h index 999124459..aeca6761f 100644 --- a/include/linux/tracefs.h +++ b/include/linux/tracefs.h @@ -21,6 +21,35 @@ struct file_operations; #ifdef CONFIG_TRACING +struct eventfs_inode { + struct list_head e_top_files; +}; + +struct eventfs_file { + const char *name; + struct dentry *d_parent; + struct dentry *dentry; + struct list_head list; + struct eventfs_inode *ei; + const struct file_operations *fop; + const struct inode_operations *iop; + void *data; + umode_t mode; + bool created; +}; + +struct dentry *eventfs_create_events_dir(const char *name, + struct dentry *parent, + struct rw_semaphore *eventfs_rwsem); + +struct eventfs_file *eventfs_add_subsystem_dir(const char *name, + struct dentry *parent, + struct rw_semaphore *eventfs_rwsem); + +struct eventfs_file *eventfs_add_dir(const char *name, + struct eventfs_file *ef_parent, + struct rw_semaphore *eventfs_rwsem); + struct dentry *tracefs_create_file(const char *name, umode_t mode, struct dentry *parent, void *data, const struct file_operations *fops); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 79bdefe92..b895c3346 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -359,6 +359,7 @@ struct trace_array { struct dentry *options; struct dentry *percpu_dir; struct dentry *event_dir; + struct rw_semaphore eventfs_rwsem; struct trace_options *topts; struct list_head systems; struct list_head events; -- 2.40.0
