/* [<][>][^][v][top][bottom][index][help] */
DEFINITIONS
This source file includes following definitions.
- get_inotify_handle
- put_inotify_handle
- get_inotify_watch
- put_inotify_watch
- inotify_handle_get_wd
- inotify_inode_watched
- set_dentry_child_flags
- inode_find_handle
- remove_watch_no_event
- inotify_remove_watch_locked
- inotify_d_instantiate
- inotify_d_move
- inotify_inode_queue_event
- inotify_dentry_parent_queue_event
- inotify_get_cookie
- inotify_unmount_inodes
- inotify_inode_is_dead
- inotify_init
- inotify_init_watch
- inotify_destroy
- inotify_find_watch
- inotify_find_update_watch
- inotify_add_watch
- inotify_clone_watch
- inotify_evict_watch
- inotify_rm_wd
- inotify_rm_watch
- inotify_setup
/*
* fs/inotify.c - inode-based file event notifications
*
* Authors:
* John McCutchan <ttb@tentacle.dhs.org>
* Robert Love <rml@novell.com>
*
* Kernel API added by: Amy Griffis <amy.griffis@hp.com>
*
* Copyright (C) 2005 John McCutchan
* Copyright 2006 Hewlett-Packard Development Company, L.P.
*
* 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.
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/idr.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/writeback.h>
#include <linux/inotify.h>
static atomic_t inotify_cookie;
/*
* Lock ordering:
*
* dentry->d_lock (used to keep d_move() away from dentry->d_parent)
* iprune_mutex (synchronize shrink_icache_memory())
* inode_lock (protects the super_block->s_inodes list)
* inode->inotify_mutex (protects inode->inotify_watches and watches->i_list)
* inotify_handle->mutex (protects inotify_handle and watches->h_list)
*
* The inode->inotify_mutex and inotify_handle->mutex and held during execution
* of a caller's event handler. Thus, the caller must not hold any locks
* taken in their event handler while calling any of the published inotify
* interfaces.
*/
/*
* Lifetimes of the three main data structures--inotify_handle, inode, and
* inotify_watch--are managed by reference count.
*
* inotify_handle: Lifetime is from inotify_init() to inotify_destroy().
* Additional references can bump the count via get_inotify_handle() and drop
* the count via put_inotify_handle().
*
* inotify_watch: for inotify's purposes, lifetime is from inotify_add_watch()
* to remove_watch_no_event(). Additional references can bump the count via
* get_inotify_watch() and drop the count via put_inotify_watch(). The caller
* is reponsible for the final put after receiving IN_IGNORED, or when using
* IN_ONESHOT after receiving the first event. Inotify does the final put if
* inotify_destroy() is called.
*
* inode: Pinned so long as the inode is associated with a watch, from
* inotify_add_watch() to the final put_inotify_watch().
*/
/*
* struct inotify_handle - represents an inotify instance
*
* This structure is protected by the mutex 'mutex'.
*/
struct inotify_handle {
struct idr idr; /* idr mapping wd -> watch */
struct mutex mutex; /* protects this bad boy */
struct list_head watches; /* list of watches */
atomic_t count; /* reference count */
u32 last_wd; /* the last wd allocated */
const struct inotify_operations *in_ops; /* inotify caller operations */
};
static inline void get_inotify_handle(struct inotify_handle *ih)
{
atomic_inc(&ih->count);
}
static inline void put_inotify_handle(struct inotify_handle *ih)
{
if (atomic_dec_and_test(&ih->count)) {
idr_destroy(&ih->idr);
kfree(ih);
}
}
/**
* get_inotify_watch - grab a reference to an inotify_watch
* @watch: watch to grab
*/
void get_inotify_watch(struct inotify_watch *watch)
{
atomic_inc(&watch->count);
}
EXPORT_SYMBOL_GPL(get_inotify_watch);
/**
* put_inotify_watch - decrements the ref count on a given watch. cleans up
* watch references if the count reaches zero. inotify_watch is freed by
* inotify callers via the destroy_watch() op.
* @watch: watch to release
*/
void put_inotify_watch(struct inotify_watch *watch)
{
if (atomic_dec_and_test(&watch->count)) {
struct inotify_handle *ih = watch->ih;
iput(watch->inode);
ih->in_ops->destroy_watch(watch);
put_inotify_handle(ih);
}
}
EXPORT_SYMBOL_GPL(put_inotify_watch);
/*
* inotify_handle_get_wd - returns the next WD for use by the given handle
*
* Callers must hold ih->mutex. This function can sleep.
*/
static int inotify_handle_get_wd(struct inotify_handle *ih,
struct inotify_watch *watch)
{
int ret;
do {
if (unlikely(!idr_pre_get(&ih->idr, GFP_KERNEL)))
return -ENOSPC;
ret = idr_get_new_above(&ih->idr, watch, ih->last_wd+1, &watch->wd);
} while (ret == -EAGAIN);
if (likely(!ret))
ih->last_wd = watch->wd;
return ret;
}
/*
* inotify_inode_watched - returns nonzero if there are watches on this inode
* and zero otherwise. We call this lockless, we do not care if we race.
*/
static inline int inotify_inode_watched(struct inode *inode)
{
return !list_empty(&inode->inotify_watches);
}
/*
* Get child dentry flag into synch with parent inode.
* Flag should always be clear for negative dentrys.
*/
static void set_dentry_child_flags(struct inode *inode, int watched)
{
struct dentry *alias;
spin_lock(&dcache_lock);
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
struct dentry *child;
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_INOTIFY_PARENT_WATCHED;
else
child->d_flags &=~DCACHE_INOTIFY_PARENT_WATCHED;
spin_unlock(&child->d_lock);
}
}
spin_unlock(&dcache_lock);
}
/*
* inotify_find_handle - find the watch associated with the given inode and
* handle
*
* Callers must hold inode->inotify_mutex.
*/
static struct inotify_watch *inode_find_handle(struct inode *inode,
struct inotify_handle *ih)
{
struct inotify_watch *watch;
list_for_each_entry(watch, &inode->inotify_watches, i_list) {
if (watch->ih == ih)
return watch;
}
return NULL;
}
/*
* remove_watch_no_event - remove watch without the IN_IGNORED event.
*
* Callers must hold both inode->inotify_mutex and ih->mutex.
*/
static void remove_watch_no_event(struct inotify_watch *watch,
struct inotify_handle *ih)
{
list_del(&watch->i_list);
list_del(&watch->h_list);
if (!inotify_inode_watched(watch->inode))
set_dentry_child_flags(watch->inode, 0);
idr_remove(&ih->idr, watch->wd);
}
/**
* inotify_remove_watch_locked - Remove a watch from both the handle and the
* inode. Sends the IN_IGNORED event signifying that the inode is no longer
* watched. May be invoked from a caller's event handler.
* @ih: inotify handle associated with watch
* @watch: watch to remove
*
* Callers must hold both inode->inotify_mutex and ih->mutex.
*/
void inotify_remove_watch_locked(struct inotify_handle *ih,
struct inotify_watch *watch)
{
remove_watch_no_event(watch, ih);
ih->in_ops->handle_event(watch, watch->wd, IN_IGNORED, 0, NULL, NULL);
}
EXPORT_SYMBOL_GPL(inotify_remove_watch_locked);
/* Kernel API for producing events */
/*
* inotify_d_instantiate - instantiate dcache entry for inode
*/
void inotify_d_instantiate(struct dentry *entry, struct inode *inode)
{
struct dentry *parent;
if (!inode)
return;
spin_lock(&entry->d_lock);
parent = entry->d_parent;
if (parent->d_inode && inotify_inode_watched(parent->d_inode))
entry->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
spin_unlock(&entry->d_lock);
}
/*
* inotify_d_move - dcache entry has been moved
*/
void inotify_d_move(struct dentry *entry)
{
struct dentry *parent;
parent = entry->d_parent;
if (inotify_inode_watched(parent->d_inode))
entry->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
else
entry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED;
}
/**
* inotify_inode_queue_event - queue an event to all watches on this inode
* @inode: inode event is originating from
* @mask: event mask describing this event
* @cookie: cookie for synchronization, or zero
* @name: filename, if any
* @n_inode: inode associated with name
*/
void inotify_inode_queue_event(struct inode *inode, u32 mask, u32 cookie,
const char *name, struct inode *n_inode)
{
struct inotify_watch *watch, *next;
if (!inotify_inode_watched(inode))
return;
mutex_lock(&inode->inotify_mutex);
list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
u32 watch_mask = watch->mask;
if (watch_mask & mask) {
struct inotify_handle *ih= watch->ih;
mutex_lock(&ih->mutex);
if (watch_mask & IN_ONESHOT)
remove_watch_no_event(watch, ih);
ih->in_ops->handle_event(watch, watch->wd, mask, cookie,
name, n_inode);
mutex_unlock(&ih->mutex);
}
}
mutex_unlock(&inode->inotify_mutex);
}
EXPORT_SYMBOL_GPL(inotify_inode_queue_event);
/**
* inotify_dentry_parent_queue_event - queue an event to a dentry's parent
* @dentry: the dentry in question, we queue against this dentry's parent
* @mask: event mask describing this event
* @cookie: cookie for synchronization, or zero
* @name: filename, if any
*/
void inotify_dentry_parent_queue_event(struct dentry *dentry, u32 mask,
u32 cookie, const char *name)
{
struct dentry *parent;
struct inode *inode;
if (!(dentry->d_flags & DCACHE_INOTIFY_PARENT_WATCHED))
return;
spin_lock(&dentry->d_lock);
parent = dentry->d_parent;
inode = parent->d_inode;
if (inotify_inode_watched(inode)) {
dget(parent);
spin_unlock(&dentry->d_lock);
inotify_inode_queue_event(inode, mask, cookie, name,
dentry->d_inode);
dput(parent);
} else
spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL_GPL(inotify_dentry_parent_queue_event);
/**
* inotify_get_cookie - return a unique cookie for use in synchronizing events.
*/
u32 inotify_get_cookie(void)
{
return atomic_inc_return(&inotify_cookie);
}
EXPORT_SYMBOL_GPL(inotify_get_cookie);
/**
* inotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
* @list: list of inodes being unmounted (sb->s_inodes)
*
* Called with inode_lock held, protecting the unmounting super block's list
* of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
* We temporarily drop inode_lock, however, and CAN block.
*/
void inotify_unmount_inodes(struct list_head *list)
{
struct inode *inode, *next_i, *need_iput = NULL;
list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
struct inotify_watch *watch, *next_w;
struct inode *need_iput_tmp;
struct list_head *watches;
/*
* If i_count is zero, the inode cannot have any watches and
* doing an __iget/iput with MS_ACTIVE clear would actually
* evict all inodes with zero i_count from icache which is
* unnecessarily violent and may in fact be illegal to do.
*/
if (!atomic_read(&inode->i_count))
continue;
/*
* We cannot __iget() an inode in state I_CLEAR, I_FREEING, or
* I_WILL_FREE which is fine because by that point the inode
* cannot have any associated watches.
*/
if (inode->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))
continue;
need_iput_tmp = need_iput;
need_iput = NULL;
/* In case inotify_remove_watch_locked() drops a reference. */
if (inode != need_iput_tmp)
__iget(inode);
else
need_iput_tmp = NULL;
/* In case the dropping of a reference would nuke next_i. */
if ((&next_i->i_sb_list != list) &&
atomic_read(&next_i->i_count) &&
!(next_i->i_state & (I_CLEAR | I_FREEING |
I_WILL_FREE))) {
__iget(next_i);
need_iput = next_i;
}
/*
* We can safely drop inode_lock here because we hold
* references on both inode and next_i. Also no new inodes
* will be added since the umount has begun. Finally,
* iprune_mutex keeps shrink_icache_memory() away.
*/
spin_unlock(&inode_lock);
if (need_iput_tmp)
iput(need_iput_tmp);
/* for each watch, send IN_UNMOUNT and then remove it */
mutex_lock(&inode->inotify_mutex);
watches = &inode->inotify_watches;
list_for_each_entry_safe(watch, next_w, watches, i_list) {
struct inotify_handle *ih= watch->ih;
mutex_lock(&ih->mutex);
ih->in_ops->handle_event(watch, watch->wd, IN_UNMOUNT, 0,
NULL, NULL);
inotify_remove_watch_locked(ih, watch);
mutex_unlock(&ih->mutex);
}
mutex_unlock(&inode->inotify_mutex);
iput(inode);
spin_lock(&inode_lock);
}
}
EXPORT_SYMBOL_GPL(inotify_unmount_inodes);
/**
* inotify_inode_is_dead - an inode has been deleted, cleanup any watches
* @inode: inode that is about to be removed
*/
void inotify_inode_is_dead(struct inode *inode)
{
struct inotify_watch *watch, *next;
mutex_lock(&inode->inotify_mutex);
list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
struct inotify_handle *ih = watch->ih;
mutex_lock(&ih->mutex);
inotify_remove_watch_locked(ih, watch);
mutex_unlock(&ih->mutex);
}
mutex_unlock(&inode->inotify_mutex);
}
EXPORT_SYMBOL_GPL(inotify_inode_is_dead);
/* Kernel Consumer API */
/**
* inotify_init - allocate and initialize an inotify instance
* @ops: caller's inotify operations
*/
struct inotify_handle *inotify_init(const struct inotify_operations *ops)
{
struct inotify_handle *ih;
ih = kmalloc(sizeof(struct inotify_handle), GFP_KERNEL);
if (unlikely(!ih))
return ERR_PTR(-ENOMEM);
idr_init(&ih->idr);
INIT_LIST_HEAD(&ih->watches);
mutex_init(&ih->mutex);
ih->last_wd = 0;
ih->in_ops = ops;
atomic_set(&ih->count, 0);
get_inotify_handle(ih);
return ih;
}
EXPORT_SYMBOL_GPL(inotify_init);
/**
* inotify_init_watch - initialize an inotify watch
* @watch: watch to initialize
*/
void inotify_init_watch(struct inotify_watch *watch)
{
INIT_LIST_HEAD(&watch->h_list);
INIT_LIST_HEAD(&watch->i_list);
atomic_set(&watch->count, 0);
get_inotify_watch(watch); /* initial get */
}
EXPORT_SYMBOL_GPL(inotify_init_watch);
/**
* inotify_destroy - clean up and destroy an inotify instance
* @ih: inotify handle
*/
void inotify_destroy(struct inotify_handle *ih)
{
/*
* Destroy all of the watches for this handle. Unfortunately, not very
* pretty. We cannot do a simple iteration over the list, because we
* do not know the inode until we iterate to the watch. But we need to
* hold inode->inotify_mutex before ih->mutex. The following works.
*/
while (1) {
struct inotify_watch *watch;
struct list_head *watches;
struct inode *inode;
mutex_lock(&ih->mutex);
watches = &ih->watches;
if (list_empty(watches)) {
mutex_unlock(&ih->mutex);
break;
}
watch = list_first_entry(watches, struct inotify_watch, h_list);
get_inotify_watch(watch);
mutex_unlock(&ih->mutex);
inode = watch->inode;
mutex_lock(&inode->inotify_mutex);
mutex_lock(&ih->mutex);
/* make sure we didn't race with another list removal */
if (likely(idr_find(&ih->idr, watch->wd))) {
remove_watch_no_event(watch, ih);
put_inotify_watch(watch);
}
mutex_unlock(&ih->mutex);
mutex_unlock(&inode->inotify_mutex);
put_inotify_watch(watch);
}
/* free this handle: the put matching the get in inotify_init() */
put_inotify_handle(ih);
}
EXPORT_SYMBOL_GPL(inotify_destroy);
/**
* inotify_find_watch - find an existing watch for an (ih,inode) pair
* @ih: inotify handle
* @inode: inode to watch
* @watchp: pointer to existing inotify_watch
*
* Caller must pin given inode (via nameidata).
*/
s32 inotify_find_watch(struct inotify_handle *ih, struct inode *inode,
struct inotify_watch **watchp)
{
struct inotify_watch *old;
int ret = -ENOENT;
mutex_lock(&inode->inotify_mutex);
mutex_lock(&ih->mutex);
old = inode_find_handle(inode, ih);
if (unlikely(old)) {
get_inotify_watch(old); /* caller must put watch */
*watchp = old;
ret = old->wd;
}
mutex_unlock(&ih->mutex);
mutex_unlock(&inode->inotify_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(inotify_find_watch);
/**
* inotify_find_update_watch - find and update the mask of an existing watch
* @ih: inotify handle
* @inode: inode's watch to update
* @mask: mask of events to watch
*
* Caller must pin given inode (via nameidata).
*/
s32 inotify_find_update_watch(struct inotify_handle *ih, struct inode *inode,
u32 mask)
{
struct inotify_watch *old;
int mask_add = 0;
int ret;
if (mask & IN_MASK_ADD)
mask_add = 1;
/* don't allow invalid bits: we don't want flags set */
mask &= IN_ALL_EVENTS | IN_ONESHOT;
if (unlikely(!mask))
return -EINVAL;
mutex_lock(&inode->inotify_mutex);
mutex_lock(&ih->mutex);
/*
* Handle the case of re-adding a watch on an (inode,ih) pair that we
* are already watching. We just update the mask and return its wd.
*/
old = inode_find_handle(inode, ih);
if (unlikely(!old)) {
ret = -ENOENT;
goto out;
}
if (mask_add)
old->mask |= mask;
else
old->mask = mask;
ret = old->wd;
out:
mutex_unlock(&ih->mutex);
mutex_unlock(&inode->inotify_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(inotify_find_update_watch);
/**
* inotify_add_watch - add a watch to an inotify instance
* @ih: inotify handle
* @watch: caller allocated watch structure
* @inode: inode to watch
* @mask: mask of events to watch
*
* Caller must pin given inode (via nameidata).
* Caller must ensure it only calls inotify_add_watch() once per watch.
* Calls inotify_handle_get_wd() so may sleep.
*/
s32 inotify_add_watch(struct inotify_handle *ih, struct inotify_watch *watch,
struct inode *inode, u32 mask)
{
int ret = 0;
int newly_watched;
/* don't allow invalid bits: we don't want flags set */
mask &= IN_ALL_EVENTS | IN_ONESHOT;
if (unlikely(!mask))
return -EINVAL;
watch->mask = mask;
mutex_lock(&inode->inotify_mutex);
mutex_lock(&ih->mutex);
/* Initialize a new watch */
ret = inotify_handle_get_wd(ih, watch);
if (unlikely(ret))
goto out;
ret = watch->wd;
/* save a reference to handle and bump the count to make it official */
get_inotify_handle(ih);
watch->ih = ih;
/*
* Save a reference to the inode and bump the ref count to make it
* official. We hold a reference to nameidata, which makes this safe.
*/
watch->inode = igrab(inode);
/* Add the watch to the handle's and the inode's list */
newly_watched = !inotify_inode_watched(inode);
list_add(&watch->h_list, &ih->watches);
list_add(&watch->i_list, &inode->inotify_watches);
/*
* Set child flags _after_ adding the watch, so there is no race
* windows where newly instantiated children could miss their parent's
* watched flag.
*/
if (newly_watched)
set_dentry_child_flags(inode, 1);
out:
mutex_unlock(&ih->mutex);
mutex_unlock(&inode->inotify_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(inotify_add_watch);
/**
* inotify_clone_watch - put the watch next to existing one
* @old: already installed watch
* @new: new watch
*
* Caller must hold the inotify_mutex of inode we are dealing with;
* it is expected to remove the old watch before unlocking the inode.
*/
s32 inotify_clone_watch(struct inotify_watch *old, struct inotify_watch *new)
{
struct inotify_handle *ih = old->ih;
int ret = 0;
new->mask = old->mask;
new->ih = ih;
mutex_lock(&ih->mutex);
/* Initialize a new watch */
ret = inotify_handle_get_wd(ih, new);
if (unlikely(ret))
goto out;
ret = new->wd;
get_inotify_handle(ih);
new->inode = igrab(old->inode);
list_add(&new->h_list, &ih->watches);
list_add(&new->i_list, &old->inode->inotify_watches);
out:
mutex_unlock(&ih->mutex);
return ret;
}
void inotify_evict_watch(struct inotify_watch *watch)
{
get_inotify_watch(watch);
mutex_lock(&watch->ih->mutex);
inotify_remove_watch_locked(watch->ih, watch);
mutex_unlock(&watch->ih->mutex);
}
/**
* inotify_rm_wd - remove a watch from an inotify instance
* @ih: inotify handle
* @wd: watch descriptor to remove
*
* Can sleep.
*/
int inotify_rm_wd(struct inotify_handle *ih, u32 wd)
{
struct inotify_watch *watch;
struct inode *inode;
mutex_lock(&ih->mutex);
watch = idr_find(&ih->idr, wd);
if (unlikely(!watch)) {
mutex_unlock(&ih->mutex);
return -EINVAL;
}
get_inotify_watch(watch);
inode = watch->inode;
mutex_unlock(&ih->mutex);
mutex_lock(&inode->inotify_mutex);
mutex_lock(&ih->mutex);
/* make sure that we did not race */
if (likely(idr_find(&ih->idr, wd) == watch))
inotify_remove_watch_locked(ih, watch);
mutex_unlock(&ih->mutex);
mutex_unlock(&inode->inotify_mutex);
put_inotify_watch(watch);
return 0;
}
EXPORT_SYMBOL_GPL(inotify_rm_wd);
/**
* inotify_rm_watch - remove a watch from an inotify instance
* @ih: inotify handle
* @watch: watch to remove
*
* Can sleep.
*/
int inotify_rm_watch(struct inotify_handle *ih,
struct inotify_watch *watch)
{
return inotify_rm_wd(ih, watch->wd);
}
EXPORT_SYMBOL_GPL(inotify_rm_watch);
/*
* inotify_setup - core initialization function
*/
static int __init inotify_setup(void)
{
atomic_set(&inotify_cookie, 0);
return 0;
}
module_init(inotify_setup);