/*
* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/dcache.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/srcu.h>
#include <linux/fsnotify_backend.h>
#include "fsnotify.h"
/*
* Clear all of the marks on an inode when it is being evicted from core
*/
void __fsnotify_inode_delete(struct inode *inode)
{
fsnotify_clear_marks_by_inode(inode);
}
EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
/*
* Given an inode, first check if we care what happens to our children. Inotify
* and dnotify both tell their parents about events. If we care about any event
* on a child we run all of our children and set a dentry flag saying that the
* parent cares. Thus when an event happens on a child it can quickly tell if
* if there is a need to find a parent and send the event to the parent.
*/
void __fsnotify_update_child_dentry_flags(struct inode *inode)
{
struct dentry *alias;
int watched;
if (!S_ISDIR(inode->i_mode))
return;
/* determine if the children should tell inode about their events */
watched = fsnotify_inode_watches_children(inode);
spin_lock(&dcache_lock);
/* run all of the dentries associated with this inode. Since this is a
* directory, there damn well better only be one item on this list */
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
struct dentry *child;
/* run all of the children of the original inode and fix their
* d_flags to indicate parental interest (their parent is the
* original inode) */
list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
if (!child->d_inode)
continue;
spin_lock(&child->d_lock);
if (watched)
child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
else
child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
spin_unlock(&child->d_lock);
}
}
spin_unlock(&dcache_lock);
}
/* Notify this dentry's parent about a child's events. */
void __fsnotify_parent(struct file *file, struct dentry *dentry, __u32 mask)
{
struct dentry *parent;
struct inode *p_inode;
bool send = false;
bool should_update_children = false;
if (file)
dentry = file->f_path.dentry;
if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
return;
spin_lock(&dentry->d_lock);
parent = dentry->d_parent;
p_inode = parent->d_inode;
if (fsnotify_inode_watches_children(p_inode)) {
if (p_inode->i_fsnotify_mask & mask) {
dget(parent);
send = true;
}
} else {
/*
* The parent doesn't care about events on it's children but
* at least one child thought it did. We need to run all the
* children and update their d_flags to let them know p_inode
* doesn't care about them any more.
*/
dget(parent);
should_update_children = true;
}
spin_unlock(&dentry->d_lock);
if (send) {
/* we are notifying a parent so come up with the new mask which
* specifies these are events which came from a child. */
mask |= FS_EVENT_ON_CHILD;
if (file)
fsnotify(p_inode, mask, file, FSNOTIFY_EVENT_FILE,
dentry->d_name.name, 0);
else
fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
dentry->d_name.name, 0);
dput(parent);
}
if (unlikely(should_update_children)) {
__fsnotify_update_child_dentry_flags(p_inode);
dput(parent);
}
}
EXPORT_SYMBOL_GPL(__fsnotify_parent);
static void send_to_group(__u32 mask,
struct fsnotify_group *group,
void *data, int data_is, const char *file_name,
u32 cookie, struct fsnotify_event **event,
struct inode *to_tell)
{
if (!group->ops->should_send_event(group, to_tell, mask,
data, data_is))
return;
if (!*event) {
*event = fsnotify_create_event(to_tell, mask, data,
data_is, file_name,
cookie, GFP_KERNEL);
/*
* shit, we OOM'd and now we can't tell, maybe
* someday someone else will want to do something
* here
*/
if (!*event)
return;
}
group->ops->handle_event(group, *event);
}
static bool needed_by_vfsmount(__u32 test_mask, void *data, int data_is)
{
struct path *path;
if (data_is == FSNOTIFY_EVENT_PATH)
path = (struct path *)data;
else if (data_is == FSNOTIFY_EVENT_FILE)
path = &((struct file *)data)->f_path;
else
return false;
/* hook in this when mnt->mnt_fsnotify_mask is defined */
/* return (test_mask & path->mnt->mnt_fsnotify_mask); */
return false;
}
/*
* This is the main call to fsnotify. The VFS calls into hook specific functions
* in linux/fsnotify.h. Those functions then in turn call here. Here will call
* out to all of the registered fsnotify_group. Those groups can then use the
* notification event in whatever means they feel necessary.
*/
void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is, const char *file_name, u32 cookie)
{
struct fsnotify_group *group;
struct fsnotify_event *event = NULL;
int idx;
/* global tests shouldn't care about events on child only the specific event */
__u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
/* if no fsnotify listeners, nothing to do */
if (list_empty(&fsnotify_inode_groups) &&
list_empty(&fsnotify_vfsmount_groups))
return;
/* if none of the directed listeners or vfsmount listeners care */
if (!(test_mask & fsnotify_inode_mask) &&
!(test_mask & fsnotify_vfsmount_mask))
return;
/* if this inode's directed listeners don't care and nothing on the vfsmount
* listeners list cares, nothing to do */
if (!(test_mask & to_tell->i_fsnotify_mask) &&
!needed_by_vfsmount(test_mask, data, data_is))
return;
/*
* SRCU!! the groups list is very very much read only and the path is
* very hot. The VAST majority of events are not going to need to do
* anything other than walk the list so it's crazy to pre-allocate.
*/
idx = srcu_read_lock(&fsnotify_grp_srcu);
if (test_mask & to_tell->i_fsnotify_mask) {
list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list) {
if (test_mask & group->mask) {
send_to_group(mask, group, data, data_is,
file_name, cookie, &event, to_tell);
}
}
}
if (needed_by_vfsmount(test_mask, data, data_is)) {
list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list) {
if (test_mask & group->mask) {
send_to_group(mask, group, data, data_is,
file_name, cookie, &event, to_tell);
}
}
}
srcu_read_unlock(&fsnotify_grp_srcu, idx);
/*
* fsnotify_create_event() took a reference so the event can't be cleaned
* up while we are still trying to add it to lists, drop that one.
*/
if (event)
fsnotify_put_event(event);
}
EXPORT_SYMBOL_GPL(fsnotify);
static __init int fsnotify_init(void)
{
return init_srcu_struct(&fsnotify_grp_srcu);
}
subsys_initcall(fsnotify_init);
