Re: [PATCH v2 2/9] eventfs: adding eventfs dir add functions

On 08-May-2023, at 3:02 PM, Zheng Yejian zhengyejian1@huawei.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@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/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@goodmis.org
• • Copyright (C) 2020-22 VMware Inc, author: Ajay Kaher akaher@vmware.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;