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eventfs: Implement eventfs lookup, read, open functions 

Add the inode_operations, file_operations, and helper functions to eventfs:
dcache_dir_open_wrapper()
eventfs_root_lookup()
eventfs_release()
eventfs_set_ef_status_free()
eventfs_post_create_dir()

The inode_operations and file_operations functions will be called from the
VFS layer.

create_file() and create_dir() are added as stub functions and will be
filled in later.

Link: https://lkml.kernel.org/r/1690568452-46553-7-git-send-email-akaher@vmware.com

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>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Ajay Kaher 2023-07-28 23:50:48 +05:30 committed by Steven Rostedt (Google)
parent 88f349b4a8
commit 6394044955
2 changed files with 306 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

304
fs/tracefs/event_inode.c
View File

@ -31,6 +31,8 @@ struct eventfs_inode {
* struct eventfs_file - hold the properties of the eventfs files and
* directories.
* @name: the name of the file or directory to create
* @d_parent: holds parent's dentry
* @dentry: once accessed holds dentry
* @list: file or directory to be added to parent directory
* @ei: list of files and directories within directory
* @fop: file_operations for file or directory
@ -40,22 +42,320 @@ struct eventfs_inode {
*/
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;
union {
struct list_head del_list; /* list of eventfs_file to delete */
struct rcu_head rcu; /* eventfs_file to delete */
unsigned long is_freed; /* Freed if one of the above is set */
};
void *data;
umode_t mode;
};
static DEFINE_MUTEX(eventfs_mutex);
DEFINE_STATIC_SRCU(eventfs_srcu);
static struct dentry *eventfs_root_lookup(struct inode *dir,
struct dentry *dentry,
unsigned int flags);
static int dcache_dir_open_wrapper(struct inode *inode, struct file *file);
static int eventfs_release(struct inode *inode, struct file *file);
static const struct inode_operations eventfs_root_dir_inode_operations = {
.lookup = eventfs_root_lookup,
};
static const struct file_operations eventfs_file_operations = {
.open = dcache_dir_open_wrapper,
.read = generic_read_dir,
.iterate_shared = dcache_readdir,
.llseek = generic_file_llseek,
.release = eventfs_release,
};
/**
* create_file - create a file in the tracefs filesystem
* @name: the name of the file to create.
* @mode: the permission that the file should have.
* @parent: parent dentry for this file.
* @data: something that the caller will want to get to later on.
* @fop: struct file_operations that should be used for this file.
*
* This is the basic "create a file" function for tracefs. It allows for a
* wide range of flexibility in creating a file.
*
* This function will return a pointer to a dentry if it succeeds. This
* pointer must be passed to the tracefs_remove() function when the file is
* to be removed (no automatic cleanup happens if your module is unloaded,
* you are responsible here.) If an error occurs, %NULL will be returned.
*
* If tracefs is not enabled in the kernel, the value -%ENODEV will be
* returned.
*/
static struct dentry *create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fop)
{
return NULL;
};
/**
* create_dir - create a dir in the tracefs filesystem
* @name: the name of the file to create.
* @parent: parent dentry for this file.
* @data: something that the caller will want to get to later on.
*
* This is the basic "create a dir" function for eventfs. It allows for a
* wide range of flexibility in creating a dir.
*
* This function will return a pointer to a dentry if it succeeds. This
* pointer must be passed to the tracefs_remove() function when the file is
* to be removed (no automatic cleanup happens if your module is unloaded,
* you are responsible here.) If an error occurs, %NULL will be returned.
*
* If tracefs is not enabled in the kernel, the value -%ENODEV will be
* returned.
*/
static struct dentry *create_dir(const char *name, struct dentry *parent, void *data)
{
return NULL;
}
/**
* eventfs_set_ef_status_free - set the ef->status to free
* @dentry: dentry who's status to be freed
*
* eventfs_set_ef_status_free will be called if no more
* references remain
*/
void eventfs_set_ef_status_free(struct dentry *dentry)
{
struct tracefs_inode *ti_parent;
struct eventfs_file *ef;
mutex_lock(&eventfs_mutex);
ti_parent = get_tracefs(dentry->d_parent->d_inode);
if (!ti_parent || !(ti_parent->flags & TRACEFS_EVENT_INODE))
goto out;
ef = dentry->d_fsdata;
if (!ef)
goto out;
dentry->d_fsdata = NULL;
ef->dentry = NULL;
out:
mutex_unlock(&eventfs_mutex);
}
/**
* eventfs_post_create_dir - post create dir routine
* @ef: eventfs_file of recently created dir
*
* Map the meta-data of files within an eventfs dir to their parent dentry
*/
static void eventfs_post_create_dir(struct eventfs_file *ef)
{
struct eventfs_file *ef_child;
struct tracefs_inode *ti;
/* srcu lock already held */
/* fill parent-child relation */
list_for_each_entry_srcu(ef_child, &ef->ei->e_top_files, list,
srcu_read_lock_held(&eventfs_srcu)) {
ef_child->d_parent = ef->dentry;
}
ti = get_tracefs(ef->dentry->d_inode);
ti->private = ef->ei;
}
/**
* create_dentry - helper function to create dentry
* @ef: eventfs_file of file or directory to create
* @parent: parent dentry
* @lookup: true if called from lookup routine
*
* Used to create a dentry for file/dir, executes post dentry creation routine
*/
static struct dentry *
create_dentry(struct eventfs_file *ef, struct dentry *parent, bool lookup)
{
bool invalidate = false;
struct dentry *dentry;
mutex_lock(&eventfs_mutex);
if (ef->is_freed) {
mutex_unlock(&eventfs_mutex);
return NULL;
}
if (ef->dentry) {
dentry = ef->dentry;
/* On dir open, up the ref count */
if (!lookup)
dget(dentry);
mutex_unlock(&eventfs_mutex);
return dentry;
}
mutex_unlock(&eventfs_mutex);
if (!lookup)
inode_lock(parent->d_inode);
if (ef->ei)
dentry = create_dir(ef->name, parent, ef->data);
else
dentry = create_file(ef->name, ef->mode, parent,
ef->data, ef->fop);
if (!lookup)
inode_unlock(parent->d_inode);
mutex_lock(&eventfs_mutex);
if (IS_ERR_OR_NULL(dentry)) {
/* If the ef was already updated get it */
dentry = ef->dentry;
if (dentry && !lookup)
dget(dentry);
mutex_unlock(&eventfs_mutex);
return dentry;
}
if (!ef->dentry && !ef->is_freed) {
ef->dentry = dentry;
if (ef->ei)
eventfs_post_create_dir(ef);
dentry->d_fsdata = ef;
} else {
/* A race here, should try again (unless freed) */
invalidate = true;
}
mutex_unlock(&eventfs_mutex);
if (invalidate)
d_invalidate(dentry);
if (lookup || invalidate)
dput(dentry);
return invalidate ? NULL : dentry;
}
static bool match_event_file(struct eventfs_file *ef, const char *name)
{
bool ret;
mutex_lock(&eventfs_mutex);
ret = !ef->is_freed && strcmp(ef->name, name) == 0;
mutex_unlock(&eventfs_mutex);
return ret;
}
/**
* eventfs_root_lookup - lookup routine to create file/dir
* @dir: in which a lookup is being done
* @dentry: file/dir dentry
* @flags: to pass as flags parameter to simple lookup
*
* Used to create a dynamic file/dir within @dir. Use the eventfs_inode
* list of meta data to find the information needed to create the file/dir.
*/
static struct dentry *eventfs_root_lookup(struct inode *dir,
struct dentry *dentry,
unsigned int flags)
{
struct tracefs_inode *ti;
struct eventfs_inode *ei;
struct eventfs_file *ef;
struct dentry *ret = NULL;
int idx;
ti = get_tracefs(dir);
if (!(ti->flags & TRACEFS_EVENT_INODE))
return NULL;
ei = ti->private;
idx = srcu_read_lock(&eventfs_srcu);
list_for_each_entry_srcu(ef, &ei->e_top_files, list,
srcu_read_lock_held(&eventfs_srcu)) {
if (!match_event_file(ef, dentry->d_name.name))
continue;
ret = simple_lookup(dir, dentry, flags);
create_dentry(ef, ef->d_parent, true);
break;
}
srcu_read_unlock(&eventfs_srcu, idx);
return ret;
}
/**
* eventfs_release - called to release eventfs file/dir
* @inode: inode to be released
* @file: file to be released (not used)
*/
static int eventfs_release(struct inode *inode, struct file *file)
{
struct tracefs_inode *ti;
struct eventfs_inode *ei;
struct eventfs_file *ef;
struct dentry *dentry;
int idx;
ti = get_tracefs(inode);
if (!(ti->flags & TRACEFS_EVENT_INODE))
return -EINVAL;
ei = ti->private;
idx = srcu_read_lock(&eventfs_srcu);
list_for_each_entry_srcu(ef, &ei->e_top_files, list,
srcu_read_lock_held(&eventfs_srcu)) {
mutex_lock(&eventfs_mutex);
dentry = ef->dentry;
mutex_unlock(&eventfs_mutex);
if (dentry)
dput(dentry);
}
srcu_read_unlock(&eventfs_srcu, idx);
return dcache_dir_close(inode, file);
}
/**
* dcache_dir_open_wrapper - eventfs open wrapper
* @inode: not used
* @file: dir to be opened (to create its child)
*
* Used to dynamically create the file/dir within @file. @file is really a
* directory and all the files/dirs of the children within @file will be
* created. If any of the files/dirs have already been created, their
* reference count will be incremented.
*/
static int dcache_dir_open_wrapper(struct inode *inode, struct file *file)
{
struct tracefs_inode *ti;
struct eventfs_inode *ei;
struct eventfs_file *ef;
struct dentry *dentry = file_dentry(file);
struct inode *f_inode = file_inode(file);
int idx;
ti = get_tracefs(f_inode);
if (!(ti->flags & TRACEFS_EVENT_INODE))
return -EINVAL;
ei = ti->private;
idx = srcu_read_lock(&eventfs_srcu);
list_for_each_entry_rcu(ef, &ei->e_top_files, list) {
create_dentry(ef, dentry, false);
}
srcu_read_unlock(&eventfs_srcu, idx);
return dcache_dir_open(inode, file);
}
/**
* eventfs_prepare_ef - helper function to prepare eventfs_file
* @name: the name of the file/directory to create.
@ -179,6 +479,7 @@ struct eventfs_file *eventfs_add_subsystem_dir(const char *name,
mutex_lock(&eventfs_mutex);
list_add_tail(&ef->list, &ei_parent->e_top_files);
ef->d_parent = parent;
mutex_unlock(&eventfs_mutex);
return ef;
}
@ -206,6 +507,7 @@ struct eventfs_file *eventfs_add_dir(const char *name,
mutex_lock(&eventfs_mutex);
list_add_tail(&ef->list, &ef_parent->ei->e_top_files);
ef->d_parent = ef_parent->dentry;
mutex_unlock(&eventfs_mutex);
return ef;
}
@ -254,6 +556,7 @@ int eventfs_add_events_file(const char *name, umode_t mode,
mutex_lock(&eventfs_mutex);
list_add_tail(&ef->list, &ei->e_top_files);
ef->d_parent = parent;
mutex_unlock(&eventfs_mutex);
return 0;
}
@ -292,6 +595,7 @@ int eventfs_add_file(const char *name, umode_t mode,
mutex_lock(&eventfs_mutex);
list_add_tail(&ef->list, &ef_parent->ei->e_top_files);
ef->d_parent = ef_parent->dentry;
mutex_unlock(&eventfs_mutex);
return 0;
}

2
fs/tracefs/internal.h
View File

@ -21,4 +21,6 @@ struct dentry *tracefs_start_creating(const char *name, struct dentry *parent);
struct dentry *tracefs_end_creating(struct dentry *dentry);
struct dentry *tracefs_failed_creating(struct dentry *dentry);
struct inode *tracefs_get_inode(struct super_block *sb);
void eventfs_set_ef_status_free(struct dentry *dentry);
#endif /* _TRACEFS_INTERNAL_H */