diff options
Diffstat (limited to 'fs/tracefs/event_inode.c')
| -rw-r--r-- | fs/tracefs/event_inode.c | 1077 |
1 files changed, 1077 insertions, 0 deletions
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c new file mode 100644 index 000000000000..2ccc849a5bda --- /dev/null +++ b/fs/tracefs/event_inode.c @@ -0,0 +1,1077 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * event_inode.c - part of tracefs, a pseudo file system for activating tracing + * + * Copyright (C) 2020-23 VMware Inc, author: Steven Rostedt <rostedt@goodmis.org> + * Copyright (C) 2020-23 VMware Inc, author: Ajay Kaher <akaher@vmware.com> + * Copyright (C) 2023 Google, author: Steven Rostedt <rostedt@goodmis.org> + * + * eventfs is used to dynamically create inodes and dentries based on the + * meta data provided by the tracing system. + * + * eventfs stores the meta-data of files/dirs and holds off on creating + * inodes/dentries of the files. When accessed, the eventfs will create the + * inodes/dentries in a just-in-time (JIT) manner. The eventfs will clean up + * and delete the inodes/dentries when they are no longer referenced. + */ +#include <linux/fsnotify.h> +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/workqueue.h> +#include <linux/security.h> +#include <linux/tracefs.h> +#include <linux/kref.h> +#include <linux/delay.h> +#include "internal.h" + +/* + * eventfs_mutex protects the eventfs_inode (ei) dentry. Any access + * to the ei->dentry must be done under this mutex and after checking + * if ei->is_freed is not set. When ei->is_freed is set, the dentry + * is on its way to being freed after the last dput() is made on it. + */ +static DEFINE_MUTEX(eventfs_mutex); + +/* + * The eventfs_inode (ei) itself is protected by SRCU. It is released from + * its parent's list and will have is_freed set (under eventfs_mutex). + * After the SRCU grace period is over and the last dput() is called + * the ei is freed. + */ +DEFINE_STATIC_SRCU(eventfs_srcu); + +/* Mode is unsigned short, use the upper bits for flags */ +enum { + EVENTFS_SAVE_MODE = BIT(16), + EVENTFS_SAVE_UID = BIT(17), + EVENTFS_SAVE_GID = BIT(18), +}; + +#define EVENTFS_MODE_MASK (EVENTFS_SAVE_MODE - 1) + +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 dcache_readdir_wrapper(struct file *file, struct dir_context *ctx); +static int eventfs_release(struct inode *inode, struct file *file); + +static void update_attr(struct eventfs_attr *attr, struct iattr *iattr) +{ + unsigned int ia_valid = iattr->ia_valid; + + if (ia_valid & ATTR_MODE) { + attr->mode = (attr->mode & ~EVENTFS_MODE_MASK) | + (iattr->ia_mode & EVENTFS_MODE_MASK) | + EVENTFS_SAVE_MODE; + } + if (ia_valid & ATTR_UID) { + attr->mode |= EVENTFS_SAVE_UID; + attr->uid = iattr->ia_uid; + } + if (ia_valid & ATTR_GID) { + attr->mode |= EVENTFS_SAVE_GID; + attr->gid = iattr->ia_gid; + } +} + +static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry, + struct iattr *iattr) +{ + const struct eventfs_entry *entry; + struct eventfs_inode *ei; + const char *name; + int ret; + + mutex_lock(&eventfs_mutex); + ei = dentry->d_fsdata; + if (ei->is_freed) { + /* Do not allow changes if the event is about to be removed. */ + mutex_unlock(&eventfs_mutex); + return -ENODEV; + } + + /* Preallocate the children mode array if necessary */ + if (!(dentry->d_inode->i_mode & S_IFDIR)) { + if (!ei->entry_attrs) { + ei->entry_attrs = kzalloc(sizeof(*ei->entry_attrs) * ei->nr_entries, + GFP_NOFS); + if (!ei->entry_attrs) { + ret = -ENOMEM; + goto out; + } + } + } + + ret = simple_setattr(idmap, dentry, iattr); + if (ret < 0) + goto out; + + /* + * If this is a dir, then update the ei cache, only the file + * mode is saved in the ei->m_children, and the ownership is + * determined by the parent directory. + */ + if (dentry->d_inode->i_mode & S_IFDIR) { + update_attr(&ei->attr, iattr); + + } else { + name = dentry->d_name.name; + + for (int i = 0; i < ei->nr_entries; i++) { + entry = &ei->entries[i]; + if (strcmp(name, entry->name) == 0) { + update_attr(&ei->entry_attrs[i], iattr); + break; + } + } + } + out: + mutex_unlock(&eventfs_mutex); + return ret; +} + +static const struct inode_operations eventfs_root_dir_inode_operations = { + .lookup = eventfs_root_lookup, + .setattr = eventfs_set_attr, +}; + +static const struct inode_operations eventfs_file_inode_operations = { + .setattr = eventfs_set_attr, +}; + +static const struct file_operations eventfs_file_operations = { + .open = dcache_dir_open_wrapper, + .read = generic_read_dir, + .iterate_shared = dcache_readdir_wrapper, + .llseek = generic_file_llseek, + .release = eventfs_release, +}; + +static void update_inode_attr(struct dentry *dentry, struct inode *inode, + struct eventfs_attr *attr, umode_t mode) +{ + if (!attr) { + inode->i_mode = mode; + return; + } + + if (attr->mode & EVENTFS_SAVE_MODE) + inode->i_mode = attr->mode & EVENTFS_MODE_MASK; + else + inode->i_mode = mode; + + if (attr->mode & EVENTFS_SAVE_UID) + inode->i_uid = attr->uid; + else + inode->i_uid = d_inode(dentry->d_parent)->i_uid; + + if (attr->mode & EVENTFS_SAVE_GID) + inode->i_gid = attr->gid; + else + inode->i_gid = d_inode(dentry->d_parent)->i_gid; +} + +/** + * 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. + * @attr: saved attributes changed by user + * @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 function creates a dentry that represents a file in the eventsfs_inode + * directory. The inode.i_private pointer will point to @data in the open() + * call. + */ +static struct dentry *create_file(const char *name, umode_t mode, + struct eventfs_attr *attr, + struct dentry *parent, void *data, + const struct file_operations *fop) +{ + struct tracefs_inode *ti; + struct dentry *dentry; + struct inode *inode; + + if (!(mode & S_IFMT)) + mode |= S_IFREG; + + if (WARN_ON_ONCE(!S_ISREG(mode))) + return NULL; + + WARN_ON_ONCE(!parent); + dentry = eventfs_start_creating(name, parent); + + if (IS_ERR(dentry)) + return dentry; + + inode = tracefs_get_inode(dentry->d_sb); + if (unlikely(!inode)) + return eventfs_failed_creating(dentry); + + /* If the user updated the directory's attributes, use them */ + update_inode_attr(dentry, inode, attr, mode); + + inode->i_op = &eventfs_file_inode_operations; + inode->i_fop = fop; + inode->i_private = data; + + ti = get_tracefs(inode); + ti->flags |= TRACEFS_EVENT_INODE; + d_instantiate(dentry, inode); + fsnotify_create(dentry->d_parent->d_inode, dentry); + return eventfs_end_creating(dentry); +}; + +/** + * create_dir - create a dir in the tracefs filesystem + * @ei: the eventfs_inode that represents the directory to create + * @parent: parent dentry for this file. + * + * This function will create a dentry for a directory represented by + * a eventfs_inode. + */ +static struct dentry *create_dir(struct eventfs_inode *ei, struct dentry *parent) +{ + struct tracefs_inode *ti; + struct dentry *dentry; + struct inode *inode; + + dentry = eventfs_start_creating(ei->name, parent); + if (IS_ERR(dentry)) + return dentry; + + inode = tracefs_get_inode(dentry->d_sb); + if (unlikely(!inode)) + return eventfs_failed_creating(dentry); + + /* If the user updated the directory's attributes, use them */ + update_inode_attr(dentry, inode, &ei->attr, + S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO); + + inode->i_op = &eventfs_root_dir_inode_operations; + inode->i_fop = &eventfs_file_operations; + + ti = get_tracefs(inode); + ti->flags |= TRACEFS_EVENT_INODE; + + inc_nlink(inode); + d_instantiate(dentry, inode); + inc_nlink(dentry->d_parent->d_inode); + fsnotify_mkdir(dentry->d_parent->d_inode, dentry); + return eventfs_end_creating(dentry); +} + +static void free_ei(struct eventfs_inode *ei) +{ + kfree_const(ei->name); + kfree(ei->d_children); + kfree(ei->entry_attrs); + kfree(ei); +} + +/** + * eventfs_set_ei_status_free - remove the dentry reference from an eventfs_inode + * @ti: the tracefs_inode of the dentry + * @dentry: dentry which has the reference to remove. + * + * Remove the association between a dentry from an eventfs_inode. + */ +void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry) +{ + struct eventfs_inode *ei; + int i; + + mutex_lock(&eventfs_mutex); + + ei = dentry->d_fsdata; + if (!ei) + goto out; + + /* This could belong to one of the files of the ei */ + if (ei->dentry != dentry) { + for (i = 0; i < ei->nr_entries; i++) { + if (ei->d_children[i] == dentry) + break; + } + if (WARN_ON_ONCE(i == ei->nr_entries)) + goto out; + ei->d_children[i] = NULL; + } else if (ei->is_freed) { + free_ei(ei); + } else { + ei->dentry = NULL; + } + + dentry->d_fsdata = NULL; + out: + mutex_unlock(&eventfs_mutex); +} + +/** + * create_file_dentry - create a dentry for a file of an eventfs_inode + * @ei: the eventfs_inode that the file will be created under + * @idx: the index into the d_children[] of the @ei + * @parent: The parent dentry of the created file. + * @name: The name of the file to create + * @mode: The mode of the file. + * @data: The data to use to set the inode of the file with on open() + * @fops: The fops of the file to be created. + * @lookup: If called by the lookup routine, in which case, dput() the created dentry. + * + * Create a dentry for a file of an eventfs_inode @ei and place it into the + * address located at @e_dentry. If the @e_dentry already has a dentry, then + * just do a dget() on it and return. Otherwise create the dentry and attach it. + */ +static struct dentry * +create_file_dentry(struct eventfs_inode *ei, int idx, + struct dentry *parent, const char *name, umode_t mode, void *data, + const struct file_operations *fops, bool lookup) +{ + struct eventfs_attr *attr = NULL; + struct dentry **e_dentry = &ei->d_children[idx]; + struct dentry *dentry; + + WARN_ON_ONCE(!inode_is_locked(parent->d_inode)); + + mutex_lock(&eventfs_mutex); + if (ei->is_freed) { + mutex_unlock(&eventfs_mutex); + return NULL; + } + /* If the e_dentry already has a dentry, use it */ + if (*e_dentry) { + /* lookup does not need to up the ref count */ + if (!lookup) + dget(*e_dentry); + mutex_unlock(&eventfs_mutex); + return *e_dentry; + } + + /* ei->entry_attrs are protected by SRCU */ + if (ei->entry_attrs) + attr = &ei->entry_attrs[idx]; + + mutex_unlock(&eventfs_mutex); + + dentry = create_file(name, mode, attr, parent, data, fops); + + mutex_lock(&eventfs_mutex); + + if (IS_ERR_OR_NULL(dentry)) { + /* + * When the mutex was released, something else could have + * created the dentry for this e_dentry. In which case + * use that one. + * + * If ei->is_freed is set, the e_dentry is currently on its + * way to being freed, don't return it. If e_dentry is NULL + * it means it was already freed. + */ + if (ei->is_freed) + dentry = NULL; + else + dentry = *e_dentry; + /* The lookup does not need to up the dentry refcount */ + if (dentry && !lookup) + dget(dentry); + mutex_unlock(&eventfs_mutex); + return dentry; + } + + if (!*e_dentry && !ei->is_freed) { + *e_dentry = dentry; + dentry->d_fsdata = ei; + } else { + /* + * Should never happen unless we get here due to being freed. + * Otherwise it means two dentries exist with the same name. + */ + WARN_ON_ONCE(!ei->is_freed); + dentry = NULL; + } + mutex_unlock(&eventfs_mutex); + + if (lookup) + dput(dentry); + + return dentry; +} + +/** + * eventfs_post_create_dir - post create dir routine + * @ei: eventfs_inode 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_inode *ei) +{ + struct eventfs_inode *ei_child; + struct tracefs_inode *ti; + + lockdep_assert_held(&eventfs_mutex); + + /* srcu lock already held */ + /* fill parent-child relation */ + list_for_each_entry_srcu(ei_child, &ei->children, list, + srcu_read_lock_held(&eventfs_srcu)) { + ei_child->d_parent = ei->dentry; + } + + ti = get_tracefs(ei->dentry->d_inode); + ti->private = ei; +} + +/** + * create_dir_dentry - Create a directory dentry for the eventfs_inode + * @pei: The eventfs_inode parent of ei. + * @ei: The eventfs_inode to create the directory for + * @parent: The dentry of the parent of this directory + * @lookup: True if this is called by the lookup code + * + * This creates and attaches a directory dentry to the eventfs_inode @ei. + */ +static struct dentry * +create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei, + struct dentry *parent, bool lookup) +{ + struct dentry *dentry = NULL; + + WARN_ON_ONCE(!inode_is_locked(parent->d_inode)); + + mutex_lock(&eventfs_mutex); + if (pei->is_freed || ei->is_freed) { + mutex_unlock(&eventfs_mutex); + return NULL; + } + if (ei->dentry) { + /* If the dentry already has a dentry, use it */ + dentry = ei->dentry; + /* lookup does not need to up the ref count */ + if (!lookup) + dget(dentry); + mutex_unlock(&eventfs_mutex); + return dentry; + } + mutex_unlock(&eventfs_mutex); + + dentry = create_dir(ei, parent); + + mutex_lock(&eventfs_mutex); + + if (IS_ERR_OR_NULL(dentry) && !ei->is_freed) { + /* + * When the mutex was released, something else could have + * created the dentry for this e_dentry. In which case + * use that one. + * + * If ei->is_freed is set, the e_dentry is currently on its + * way to being freed. + */ + dentry = ei->dentry; + if (dentry && !lookup) + dget(dentry); + mutex_unlock(&eventfs_mutex); + return dentry; + } + + if (!ei->dentry && !ei->is_freed) { + ei->dentry = dentry; + eventfs_post_create_dir(ei); + dentry->d_fsdata = ei; + } else { + /* + * Should never happen unless we get here due to being freed. + * Otherwise it means two dentries exist with the same name. + */ + WARN_ON_ONCE(!ei->is_freed); + dentry = NULL; + } + mutex_unlock(&eventfs_mutex); + + if (lookup) + dput(dentry); + + return dentry; +} + +/** + * eventfs_root_lookup - lookup routine to create file/dir + * @dir: in which a lookup is being done + * @dentry: file/dir dentry + * @flags: Just passed to simple_lookup() + * + * Used to create dynamic file/dir with-in @dir, search with-in @ei + * list, if @dentry found go ahead and create the file/dir + */ + +static struct dentry *eventfs_root_lookup(struct inode *dir, + struct dentry *dentry, + unsigned int flags) +{ + const struct file_operations *fops; + const struct eventfs_entry *entry; + struct eventfs_inode *ei_child; + struct tracefs_inode *ti; + struct eventfs_inode *ei; + struct dentry *ei_dentry = NULL; + struct dentry *ret = NULL; + const char *name = dentry->d_name.name; + bool created = false; + umode_t mode; + void *data; + int idx; + int i; + int r; + + ti = get_tracefs(dir); + if (!(ti->flags & TRACEFS_EVENT_INODE)) + return NULL; + + /* Grab srcu to prevent the ei from going away */ + idx = srcu_read_lock(&eventfs_srcu); + + /* + * Grab the eventfs_mutex to consistent value from ti->private. + * This s + */ + mutex_lock(&eventfs_mutex); + ei = READ_ONCE(ti->private); + if (ei && !ei->is_freed) + ei_dentry = READ_ONCE(ei->dentry); + mutex_unlock(&eventfs_mutex); + + if (!ei || !ei_dentry) + goto out; + + data = ei->data; + + list_for_each_entry_srcu(ei_child, &ei->children, list, + srcu_read_lock_held(&eventfs_srcu)) { + if (strcmp(ei_child->name, name) != 0) + continue; + ret = simple_lookup(dir, dentry, flags); + if (IS_ERR(ret)) + goto out; + create_dir_dentry(ei, ei_child, ei_dentry, true); + created = true; + break; + } + + if (created) + goto out; + + for (i = 0; i < ei->nr_entries; i++) { + entry = &ei->entries[i]; + if (strcmp(name, entry->name) == 0) { + void *cdata = data; + mutex_lock(&eventfs_mutex); + /* If ei->is_freed, then the event itself may be too */ + if (!ei->is_freed) + r = entry->callback(name, &mode, &cdata, &fops); + else + r = -1; + mutex_unlock(&eventfs_mutex); + if (r <= 0) + continue; + ret = simple_lookup(dir, dentry, flags); + if (IS_ERR(ret)) + goto out; + create_file_dentry(ei, i, ei_dentry, name, mode, cdata, + fops, true); + break; + } + } + out: + srcu_read_unlock(&eventfs_srcu, idx); + return ret; +} + +struct dentry_list { + void *cursor; + struct dentry **dentries; +}; + +/** + * 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 dentry_list *dlist = file->private_data; + void *cursor; + int i; + + ti = get_tracefs(inode); + if (!(ti->flags & TRACEFS_EVENT_INODE)) + return -EINVAL; + + if (WARN_ON_ONCE(!dlist)) + return -EINVAL; + + for (i = 0; dlist->dentries && dlist->dentries[i]; i++) { + dput(dlist->dentries[i]); + } + + cursor = dlist->cursor; + kfree(dlist->dentries); + kfree(dlist); + file->private_data = cursor; + return dcache_dir_close(inode, file); +} + +static int add_dentries(struct dentry ***dentries, struct dentry *d, int cnt) +{ + struct dentry **tmp; + + tmp = krealloc(*dentries, sizeof(d) * (cnt + 2), GFP_NOFS); + if (!tmp) + return -1; + tmp[cnt] = d; + tmp[cnt + 1] = NULL; + *dentries = tmp; + return 0; +} + +/** + * dcache_dir_open_wrapper - eventfs open wrapper + * @inode: not used + * @file: dir to be opened (to create it's children) + * + * Used to dynamic create file/dir with-in @file, all the + * file/dir will be created. If already created then references + * will be increased + */ +static int dcache_dir_open_wrapper(struct inode *inode, struct file *file) +{ + const struct file_operations *fops; + const struct eventfs_entry *entry; + struct eventfs_inode *ei_child; + struct tracefs_inode *ti; + struct eventfs_inode *ei; + struct dentry_list *dlist; + struct dentry **dentries = NULL; + struct dentry *parent = file_dentry(file); + struct dentry *d; + struct inode *f_inode = file_inode(file); + const char *name = parent->d_name.name; + umode_t mode; + void *data; + int cnt = 0; + int idx; + int ret; + int i; + int r; + + ti = get_tracefs(f_inode); + if (!(ti->flags & TRACEFS_EVENT_INODE)) + return -EINVAL; + + if (WARN_ON_ONCE(file->private_data)) + return -EINVAL; + + idx = srcu_read_lock(&eventfs_srcu); + + mutex_lock(&eventfs_mutex); + ei = READ_ONCE(ti->private); + mutex_unlock(&eventfs_mutex); + + if (!ei) { + srcu_read_unlock(&eventfs_srcu, idx); + return -EINVAL; + } + + + data = ei->data; + + dlist = kmalloc(sizeof(*dlist), GFP_KERNEL); + if (!dlist) { + srcu_read_unlock(&eventfs_srcu, idx); + return -ENOMEM; + } + + inode_lock(parent->d_inode); + list_for_each_entry_srcu(ei_child, &ei->children, list, + srcu_read_lock_held(&eventfs_srcu)) { + d = create_dir_dentry(ei, ei_child, parent, false); + if (d) { + ret = add_dentries(&dentries, d, cnt); + if (ret < 0) + break; + cnt++; + } + } + + for (i = 0; i < ei->nr_entries; i++) { + void *cdata = data; + entry = &ei->entries[i]; + name = entry->name; + mutex_lock(&eventfs_mutex); + /* If ei->is_freed, then the event itself may be too */ + if (!ei->is_freed) + r = entry->callback(name, &mode, &cdata, &fops); + else + r = -1; + mutex_unlock(&eventfs_mutex); + if (r <= 0) + continue; + d = create_file_dentry(ei, i, parent, name, mode, cdata, fops, false); + if (d) { + ret = add_dentries(&dentries, d, cnt); + if (ret < 0) + break; + cnt++; + } + } + inode_unlock(parent->d_inode); + srcu_read_unlock(&eventfs_srcu, idx); + ret = dcache_dir_open(inode, file); + + /* + * dcache_dir_open() sets file->private_data to a dentry cursor. + * Need to save that but also save all the dentries that were + * opened by this function. + */ + dlist->cursor = file->private_data; + dlist->dentries = dentries; + file->private_data = dlist; + return ret; +} + +/* + * This just sets the file->private_data back to the cursor and back. + */ +static int dcache_readdir_wrapper(struct file *file, struct dir_context *ctx) +{ + struct dentry_list *dlist = file->private_data; + int ret; + + file->private_data = dlist->cursor; + ret = dcache_readdir(file, ctx); + dlist->cursor = file->private_data; + file->private_data = dlist; + return ret; +} + +/** + * eventfs_create_dir - Create the eventfs_inode for this directory + * @name: The name of the directory to create. + * @parent: The eventfs_inode of the parent directory. + * @entries: A list of entries that represent the files under this directory + * @size: The number of @entries + * @data: The default data to pass to the files (an entry may override it). + * + * This function creates the descriptor to represent a directory in the + * eventfs. This descriptor is an eventfs_inode, and it is returned to be + * used to create other children underneath. + * + * The @entries is an array of eventfs_entry structures which has: + * const char *name + * eventfs_callback callback; + * + * The name is the name of the file, and the callback is a pointer to a function + * that will be called when the file is reference (either by lookup or by + * reading a directory). The callback is of the prototype: + * + * int callback(const char *name, umode_t *mode, void **data, + * const struct file_operations **fops); + * + * When a file needs to be created, this callback will be called with + * name = the name of the file being created (so that the same callback + * may be used for multiple files). + * mode = a place to set the file's mode + * data = A pointer to @data, and the callback may replace it, which will + * cause the file created to pass the new data to the open() call. + * fops = the fops to use for the created file. + * + * NB. @callback is called while holding internal locks of the eventfs + * system. The callback must not call any code that might also call into + * the tracefs or eventfs system or it will risk creating a deadlock. + */ +struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode *parent, + const struct eventfs_entry *entries, + int size, void *data) +{ + struct eventfs_inode *ei; + + if (!parent) + return ERR_PTR(-EINVAL); + + ei = kzalloc(sizeof(*ei), GFP_KERNEL); + if (!ei) + return ERR_PTR(-ENOMEM); + + ei->name = kstrdup_const(name, GFP_KERNEL); + if (!ei->name) { + kfree(ei); + return ERR_PTR(-ENOMEM); + } + + if (size) { + ei->d_children = kzalloc(sizeof(*ei->d_children) * size, GFP_KERNEL); + if (!ei->d_children) { + kfree_const(ei->name); + kfree(ei); + return ERR_PTR(-ENOMEM); + } + } + + ei->entries = entries; + ei->nr_entries = size; + ei->data = data; + INIT_LIST_HEAD(&ei->children); + INIT_LIST_HEAD(&ei->list); + + mutex_lock(&eventfs_mutex); + if (!parent->is_freed) { + list_add_tail(&ei->list, &parent->children); + ei->d_parent = parent->dentry; + } + mutex_unlock(&eventfs_mutex); + + /* Was the parent freed? */ + if (list_empty(&ei->list)) { + free_ei(ei); + ei = NULL; + } + return ei; +} + +/** + * eventfs_create_events_dir - create the top level events directory + * @name: The name of the top level directory to create. + * @parent: Parent dentry for this file in the tracefs directory. + * @entries: A list of entries that represent the files under this directory + * @size: The number of @entries + * @data: The default data to pass to the files (an entry may override it). + * + * This function creates the top of the trace event directory. + * + * See eventfs_create_dir() for use of @entries. + */ +struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry *parent, + const struct eventfs_entry *entries, + int size, void *data) +{ + struct dentry *dentry = tracefs_start_creating(name, parent); + struct eventfs_inode *ei; + struct tracefs_inode *ti; + struct inode *inode; + + if (security_locked_down(LOCKDOWN_TRACEFS)) + return NULL; + + if (IS_ERR(dentry)) + return ERR_CAST(dentry); + + ei = kzalloc(sizeof(*ei), GFP_KERNEL); + if (!ei) + goto fail_ei; + + inode = tracefs_get_inode(dentry->d_sb); + if (unlikely(!inode)) + goto fail; + + if (size) { + ei->d_children = kzalloc(sizeof(*ei->d_children) * size, GFP_KERNEL); + if (!ei->d_children) + goto fail; + } + + ei->dentry = dentry; + ei->entries = entries; + ei->nr_entries = size; + ei->data = data; + ei->name = kstrdup_const(name, GFP_KERNEL); + if (!ei->name) + goto fail; + + INIT_LIST_HEAD(&ei->children); + INIT_LIST_HEAD(&ei->list); + + ti = get_tracefs(inode); + ti->flags |= TRACEFS_EVENT_INODE | TRACEFS_EVENT_TOP_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; + + dentry->d_fsdata = ei; + + /* 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); + tracefs_end_creating(dentry); + + return ei; + + fail: + kfree(ei->d_children); + kfree(ei); + fail_ei: + tracefs_failed_creating(dentry); + return ERR_PTR(-ENOMEM); +} + +static LLIST_HEAD(free_list); + +static void eventfs_workfn(struct work_struct *work) +{ + struct eventfs_inode *ei, *tmp; + struct llist_node *llnode; + + llnode = llist_del_all(&free_list); + llist_for_each_entry_safe(ei, tmp, llnode, llist) { + /* This dput() matches the dget() from unhook_dentry() */ + for (int i = 0; i < ei->nr_entries; i++) { + if (ei->d_children[i]) + dput(ei->d_children[i]); + } + /* This should only get here if it had a dentry */ + if (!WARN_ON_ONCE(!ei->dentry)) + dput(ei->dentry); + } +} + +static DECLARE_WORK(eventfs_work, eventfs_workfn); + +static void free_rcu_ei(struct rcu_head *head) +{ + struct eventfs_inode *ei = container_of(head, struct eventfs_inode, rcu); + + if (ei->dentry) { + /* Do not free the ei until all references of dentry are gone */ + if (llist_add(&ei->llist, &free_list)) + queue_work(system_unbound_wq, &eventfs_work); + return; + } + + /* If the ei doesn't have a dentry, neither should its children */ + for (int i = 0; i < ei->nr_entries; i++) { + WARN_ON_ONCE(ei->d_children[i]); + } + + free_ei(ei); +} + +static void unhook_dentry(struct dentry *dentry) +{ + if (!dentry) + return; + /* + * Need to add a reference to the dentry that is expected by + * simple_recursive_removal(), which will include a dput(). + */ + dget(dentry); + + /* + * Also add a reference for the dput() in eventfs_workfn(). + * That is required as that dput() will free the ei after + * the SRCU grace period is over. + */ + dget(dentry); +} + +/** + * eventfs_remove_rec - remove eventfs dir or file from list + * @ei: eventfs_inode to be removed. + * @level: prevent recursion from going more than 3 levels deep. + * + * This function recursively removes eventfs_inodes which + * contains info of files and/or directories. + */ +static void eventfs_remove_rec(struct eventfs_inode *ei, int level) +{ + struct eventfs_inode *ei_child; + + if (!ei) + return; + /* + * Check recursion depth. It should never be greater than 3: + * 0 - events/ + * 1 - events/group/ + * 2 - events/group/event/ + * 3 - events/group/event/file + */ + if (WARN_ON_ONCE(level > 3)) + return; + + /* search for nested folders or files */ + list_for_each_entry_srcu(ei_child, &ei->children, list, + lockdep_is_held(&eventfs_mutex)) { + /* Children only have dentry if parent does */ + WARN_ON_ONCE(ei_child->dentry && !ei->dentry); + eventfs_remove_rec(ei_child, level + 1); + } + + + ei->is_freed = 1; + + for (int i = 0; i < ei->nr_entries; i++) { + if (ei->d_children[i]) { + /* Children only have dentry if parent does */ + WARN_ON_ONCE(!ei->dentry); + unhook_dentry(ei->d_children[i]); + } + } + + unhook_dentry(ei->dentry); + + list_del_rcu(&ei->list); + call_srcu(&eventfs_srcu, &ei->rcu, free_rcu_ei); +} + +/** + * eventfs_remove_dir - remove eventfs dir or file from list + * @ei: eventfs_inode to be removed. + * + * This function acquire the eventfs_mutex lock and call eventfs_remove_rec() + */ +void eventfs_remove_dir(struct eventfs_inode *ei) +{ + struct dentry *dentry; + + if (!ei) + return; + + mutex_lock(&eventfs_mutex); + dentry = ei->dentry; + eventfs_remove_rec(ei, 0); + mutex_unlock(&eventfs_mutex); + + /* + * If any of the ei children has a dentry, then the ei itself + * must have a dentry. + */ + if (dentry) + simple_recursive_removal(dentry, NULL); +} + +/** + * eventfs_remove_events_dir - remove the top level eventfs directory + * @ei: the event_inode returned by eventfs_create_events_dir(). + * + * This function removes the events main directory + */ +void eventfs_remove_events_dir(struct eventfs_inode *ei) +{ + struct dentry *dentry; + + dentry = ei->dentry; + eventfs_remove_dir(ei); + + /* + * Matches the dget() done by tracefs_start_creating() + * in eventfs_create_events_dir() when it the dentry was + * created. In other words, it's a normal dentry that + * sticks around while the other ei->dentry are created + * and destroyed dynamically. + */ + dput(dentry); +} |