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Message-ID: <ba8b6072-42b6-4275-83fd-5497654d77db@huawei.com>
Date: Mon, 8 May 2023 17:32:09 +0800
From: Zheng Yejian <zhengyejian1@...wei.com>
To: Ajay Kaher <akaher@...are.com>, <rostedt@...dmis.org>,
<mhiramat@...nel.org>, <shuah@...nel.org>
CC: <linux-kernel@...r.kernel.org>,
<linux-trace-kernel@...r.kernel.org>,
<linux-kselftest@...r.kernel.org>, <chinglinyu@...gle.com>,
<namit@...are.com>, <srivatsab@...are.com>,
<srivatsa@...il.mit.edu>, <amakhalov@...are.com>,
<vsirnapalli@...are.com>, <tkundu@...are.com>,
<er.ajay.kaher@...il.com>
Subject: Re: [PATCH v2 2/9] eventfs: adding eventfs dir add functions
On 2023/5/2 19:23, Ajay Kaher wrote:
> Adding eventfs_file structure which will hold properties of file or dir.
>
> Adding following functions to add dir in eventfs:
>
> eventfs_create_events_dir() will directly create events dir with-in
> tracing folder.
>
> eventfs_add_subsystem_dir() will adds the info of subsystem_dir to
> eventfs and dynamically create subsystem_dir as and when requires.
>
> eventfs_add_dir() will add the info of dir (which is with-in
> subsystem_dir) to eventfs and dynamically create these dir as
> and when requires.
>
> Signed-off-by: Ajay Kaher <akaher@...are.com>
> Co-developed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> Tested-by: Ching-lin Yu <chinglinyu@...gle.com>
> ---
> fs/tracefs/Makefile | 1 +
> fs/tracefs/event_inode.c | 252 +++++++++++++++++++++++++++++++++++++++
> include/linux/tracefs.h | 29 +++++
> kernel/trace/trace.h | 1 +
> 4 files changed, 283 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..82caba7e9
> --- /dev/null
> +++ b/fs/tracefs/event_inode.c
> @@ -0,0 +1,252 @@
> +// 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@...dmis.org>
> + * Copyright (C) 2020-22 VMware Inc, author: Ajay Kaher <akaher@...are.com>
> + *
> + * 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, skip locking if caller task already
> + * own the lock. read lock requires for lookup(), release() and these also
> + * called with-in 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_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 = kzalloc(sizeof(*ef), GFP_KERNEL);
> + if (!ef)
> + return ERR_PTR(-ENOMEM);
> +
> + ef->ei = kzalloc(sizeof(*ef->ei), GFP_KERNEL);
> + if (!ef->ei) {
> + kfree(ef);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + INIT_LIST_HEAD(&ef->ei->e_top_files);
> +
> + ef->name = kstrdup(name, GFP_KERNEL);
> + if (!ef->name) {
> + kfree(ef->ei);
> + kfree(ef);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + ef->mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
> + ef->iop = &eventfs_root_dir_inode_operations;
> + ef->fop = &eventfs_file_operations;
> + ef->dentry = NULL;
> + ef->created = false;
> + ef->d_parent = parent;
> + ef->data = eventfs_rwsem;
> +
> + eventfs_down_write(eventfs_rwsem);
> + list_add_tail(&ef->list, &ei_parent->e_top_files);
> + 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 = kzalloc(sizeof(*ef), GFP_KERNEL);
> + if (!ef)
> + return ERR_PTR(-ENOMEM);
> +
> + ef->ei = kzalloc(sizeof(*ef->ei), GFP_KERNEL);
> + if (!ef->ei) {
> + kfree(ef);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + INIT_LIST_HEAD(&ef->ei->e_top_files);
> +
> + ef->name = kstrdup(name, GFP_KERNEL);
> + if (!ef->name) {
> + kfree(ef->ei);
> + kfree(ef);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + ef->mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
> + ef->iop = &eventfs_root_dir_inode_operations;
> + ef->fop = &eventfs_file_operations;
> + ef->created = false;
> + ef->dentry = NULL;
> + ef->d_parent = NULL;
> + ef->data = eventfs_rwsem;
> +
> + eventfs_down_write(eventfs_rwsem);
> + list_add_tail(&ef->list, &ef_parent->ei->e_top_files);
> + eventfs_up_write(eventfs_rwsem);
> + return ef;
> +}
Hi,
eventfs_add_subsystem_dir() and eventfs_add_dir() are almost the same,
how about extract a common help function to simplify them, like:
+static struct eventfs_file *__eventfs_add_dir(const char *name,
+ struct dentry *d_parent,
+ struct eventfs_inode
*ei_parent,
+ struct rw_semaphore
*eventfs_rwsem)
+{
+ struct eventfs_file *ef;
+
+ ef = kzalloc(sizeof(*ef), GFP_KERNEL);
+ if (!ef)
+ return ERR_PTR(-ENOMEM);
+
+ ef->ei = kzalloc(sizeof(*ef->ei), GFP_KERNEL);
+ if (!ef->ei) {
+ kfree(ef);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ INIT_LIST_HEAD(&ef->ei->e_top_files);
+
+ ef->name = kstrdup(name, GFP_KERNEL);
+ if (!ef->name) {
+ kfree(ef->ei);
+ kfree(ef);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ ef->mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
+ ef->iop = &eventfs_root_dir_inode_operations;
+ ef->fop = &eventfs_file_operations;
+ ef->dentry = NULL;
+ ef->created = false;
+ ef->d_parent = d_parent;
+ ef->data = eventfs_rwsem;
+
+ eventfs_down_write(eventfs_rwsem);
+ list_add_tail(&ef->list, &ei_parent->e_top_files);
+ eventfs_up_write(eventfs_rwsem);
+ return ef;
+}
+
+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;
+
+ if (!parent)
+ return ERR_PTR(-EINVAL);
+ ti_parent = get_tracefs(parent->d_inode);
+ ei_parent = ti_parent->private;
+ return __eventfs_add_dir(name, parent, ei_parent, eventfs_rwsem);
+}
+
+struct eventfs_file *eventfs_add_dir(const char *name,
+ struct eventfs_file *ef_parent,
+ struct rw_semaphore *eventfs_rwsem)
+{
+ if (!ef_parent)
+ return ERR_PTR(-EINVAL);
+ return __eventfs_add_dir(name, NULL, ef_parent->ei, eventfs_rwsem);
+}
--
Best regards,
Zheng Yejian
> 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 616e1aa1c..3726725c8 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;
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