FYI, all subjects should start with a capital letter:
"eventfs: Implement eventfs dir creation functions"
On Thu, 1 Jun 2023 14:30:06 +0530 Ajay Kaher akaher@vmware.com 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() directly creates events dir with-in
"within" is a proper word.
tracing folder.
eventfs_add_subsystem_dir() adds the information of subsystem_dir to eventfs and dynamically creates subsystem_dir as and when requires.
"as and when requires" does not make sense.
eventfs_add_dir() adds the information of dir (which is with-in
"within"
subsystem_dir) to eventfs and dynamically creates these dir as and when requires.
I'm guessing you want to say:
eventfs_add_dir() adds the information of the dir, within a subsystem_dir, to eventfs and dynamically creates these directories when they are accessed.
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 Link: https://lore.kernel.org/oe-lkp/202305051619.9a469a9a-yujie.liu@intel.com
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@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. 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);
What's this loop for? Something like that needs a very good explanation in a comment. Loops like these are usually a sign of a workaround for a bug in the design, or worse, simply hides an existing bug.
+}
+/**
- 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.
"allocates and fills the" ?
- */
+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;
No need for the initialization to NULL or even the false, as the kzalloc() already did that.
- 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.
You don't need to add "a pointer" we can see it's a pointer. Just say:
* @name: The name of the directory to create
Adding more makes it confusing to read.
- @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
Same with all the descriptions.
- 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)
OK, I'm going to have to really look at this. Passing in a lock to the API is just broken. We need to find a way to solve this another way.
I'm about to board a plane to JFK shortly, I'm hoping to play with this while flying back.
-- Steve
+{
- 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);
+}