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Message-ID: <A1697525-CE86-4CA3-A8D5-3452E9310A4C@vmware.com>
Date: Wed, 10 May 2023 11:25:26 +0000
From: Ajay Kaher <akaher@...are.com>
To: Zheng Yejian <zhengyejian1@...wei.com>
CC: Steven Rostedt <rostedt@...dmis.org>,
"mhiramat@...nel.org" <mhiramat@...nel.org>,
"shuah@...nel.org" <shuah@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-trace-kernel@...r.kernel.org"
<linux-trace-kernel@...r.kernel.org>,
"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
"chinglinyu@...gle.com" <chinglinyu@...gle.com>,
Nadav Amit <namit@...are.com>,
Srivatsa Bhat <srivatsab@...are.com>,
"srivatsa@...il.mit.edu" <srivatsa@...il.mit.edu>,
Alexey Makhalov <amakhalov@...are.com>,
Vasavi Sirnapalli <vsirnapalli@...are.com>,
Tapas Kundu <tkundu@...are.com>,
"er.ajay.kaher@...il.com" <er.ajay.kaher@...il.com>
Subject: Re: [PATCH v2 2/9] eventfs: adding eventfs dir add functions
> On 08-May-2023, at 3:02 PM, Zheng Yejian <zhengyejian1@...wei.com> wrote:
>
> 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);
> +}
Sounds good. Thanks for sharing code snippet. I will consider in v3.
- Ajay
>> 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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