Commit 2d9048e2 authored by Amy Griffis's avatar Amy Griffis Committed by Al Viro

[PATCH] inotify (1/5): split kernel API from userspace support

The following series of patches introduces a kernel API for inotify,
making it possible for kernel modules to benefit from inotify's
mechanism for watching inodes.  With these patches, inotify will
maintain for each caller a list of watches (via an embedded struct
inotify_watch), where each inotify_watch is associated with a
corresponding struct inode.  The caller registers an event handler and
specifies for which filesystem events their event handler should be
called per inotify_watch.
Signed-off-by: default avatarAmy Griffis <amy.griffis@hp.com>
Acked-by: default avatarRobert Love <rml@novell.com>
Acked-by: default avatarJohn McCutchan <john@johnmccutchan.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 90204e0b
...@@ -393,18 +393,30 @@ config INOTIFY ...@@ -393,18 +393,30 @@ config INOTIFY
bool "Inotify file change notification support" bool "Inotify file change notification support"
default y default y
---help--- ---help---
Say Y here to enable inotify support and the associated system Say Y here to enable inotify support. Inotify is a file change
calls. Inotify is a file change notification system and a notification system and a replacement for dnotify. Inotify fixes
replacement for dnotify. Inotify fixes numerous shortcomings in numerous shortcomings in dnotify and introduces several new features
dnotify and introduces several new features. It allows monitoring including multiple file events, one-shot support, and unmount
of both files and directories via a single open fd. Other features
include multiple file events, one-shot support, and unmount
notification. notification.
For more information, see Documentation/filesystems/inotify.txt For more information, see Documentation/filesystems/inotify.txt
If unsure, say Y. If unsure, say Y.
config INOTIFY_USER
bool "Inotify support for userspace"
depends on INOTIFY
default y
---help---
Say Y here to enable inotify support for userspace, including the
associated system calls. Inotify allows monitoring of both files and
directories via a single open fd. Events are read from the file
descriptor, which is also select()- and poll()-able.
For more information, see Documentation/filesystems/inotify.txt
If unsure, say Y.
config QUOTA config QUOTA
bool "Quota support" bool "Quota support"
help help
......
...@@ -13,6 +13,7 @@ obj-y := open.o read_write.o file_table.o buffer.o bio.o super.o \ ...@@ -13,6 +13,7 @@ obj-y := open.o read_write.o file_table.o buffer.o bio.o super.o \
ioprio.o pnode.o drop_caches.o splice.o sync.o ioprio.o pnode.o drop_caches.o splice.o sync.o
obj-$(CONFIG_INOTIFY) += inotify.o obj-$(CONFIG_INOTIFY) += inotify.o
obj-$(CONFIG_INOTIFY_USER) += inotify_user.o
obj-$(CONFIG_EPOLL) += eventpoll.o obj-$(CONFIG_EPOLL) += eventpoll.o
obj-$(CONFIG_COMPAT) += compat.o compat_ioctl.o obj-$(CONFIG_COMPAT) += compat.o compat_ioctl.o
......
This diff is collapsed.
/*
* fs/inotify_user.c - inotify support for userspace
*
* Authors:
* John McCutchan <ttb@tentacle.dhs.org>
* Robert Love <rml@novell.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/kernel.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/inotify.h>
#include <linux/syscalls.h>
#include <asm/ioctls.h>
static kmem_cache_t *watch_cachep __read_mostly;
static kmem_cache_t *event_cachep __read_mostly;
static struct vfsmount *inotify_mnt __read_mostly;
/* these are configurable via /proc/sys/fs/inotify/ */
int inotify_max_user_instances __read_mostly;
int inotify_max_user_watches __read_mostly;
int inotify_max_queued_events __read_mostly;
/*
* Lock ordering:
*
* inotify_dev->up_mutex (ensures we don't re-add the same watch)
* inode->inotify_mutex (protects inode's watch list)
* inotify_handle->mutex (protects inotify_handle's watch list)
* inotify_dev->ev_mutex (protects device's event queue)
*/
/*
* Lifetimes of the main data structures:
*
* inotify_device: Lifetime is managed by reference count, from
* sys_inotify_init() until release. Additional references can bump the count
* via get_inotify_dev() and drop the count via put_inotify_dev().
*
* inotify_user_watch: Lifetime is from create_watch() to the receipt of an
* IN_IGNORED event from inotify, or when using IN_ONESHOT, to receipt of the
* first event, or to inotify_destroy().
*/
/*
* struct inotify_device - represents an inotify instance
*
* This structure is protected by the mutex 'mutex'.
*/
struct inotify_device {
wait_queue_head_t wq; /* wait queue for i/o */
struct mutex ev_mutex; /* protects event queue */
struct mutex up_mutex; /* synchronizes watch updates */
struct list_head events; /* list of queued events */
atomic_t count; /* reference count */
struct user_struct *user; /* user who opened this dev */
struct inotify_handle *ih; /* inotify handle */
unsigned int queue_size; /* size of the queue (bytes) */
unsigned int event_count; /* number of pending events */
unsigned int max_events; /* maximum number of events */
};
/*
* struct inotify_kernel_event - An inotify event, originating from a watch and
* queued for user-space. A list of these is attached to each instance of the
* device. In read(), this list is walked and all events that can fit in the
* buffer are returned.
*
* Protected by dev->ev_mutex of the device in which we are queued.
*/
struct inotify_kernel_event {
struct inotify_event event; /* the user-space event */
struct list_head list; /* entry in inotify_device's list */
char *name; /* filename, if any */
};
/*
* struct inotify_user_watch - our version of an inotify_watch, we add
* a reference to the associated inotify_device.
*/
struct inotify_user_watch {
struct inotify_device *dev; /* associated device */
struct inotify_watch wdata; /* inotify watch data */
};
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
static int zero;
ctl_table inotify_table[] = {
{
.ctl_name = INOTIFY_MAX_USER_INSTANCES,
.procname = "max_user_instances",
.data = &inotify_max_user_instances,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec_minmax,
.strategy = &sysctl_intvec,
.extra1 = &zero,
},
{
.ctl_name = INOTIFY_MAX_USER_WATCHES,
.procname = "max_user_watches",
.data = &inotify_max_user_watches,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec_minmax,
.strategy = &sysctl_intvec,
.extra1 = &zero,
},
{
.ctl_name = INOTIFY_MAX_QUEUED_EVENTS,
.procname = "max_queued_events",
.data = &inotify_max_queued_events,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = &proc_dointvec_minmax,
.strategy = &sysctl_intvec,
.extra1 = &zero
},
{ .ctl_name = 0 }
};
#endif /* CONFIG_SYSCTL */
static inline void get_inotify_dev(struct inotify_device *dev)
{
atomic_inc(&dev->count);
}
static inline void put_inotify_dev(struct inotify_device *dev)
{
if (atomic_dec_and_test(&dev->count)) {
atomic_dec(&dev->user->inotify_devs);
free_uid(dev->user);
kfree(dev);
}
}
/*
* free_inotify_user_watch - cleans up the watch and its references
*/
static void free_inotify_user_watch(struct inotify_watch *w)
{
struct inotify_user_watch *watch;
struct inotify_device *dev;
watch = container_of(w, struct inotify_user_watch, wdata);
dev = watch->dev;
atomic_dec(&dev->user->inotify_watches);
put_inotify_dev(dev);
kmem_cache_free(watch_cachep, watch);
}
/*
* kernel_event - create a new kernel event with the given parameters
*
* This function can sleep.
*/
static struct inotify_kernel_event * kernel_event(s32 wd, u32 mask, u32 cookie,
const char *name)
{
struct inotify_kernel_event *kevent;
kevent = kmem_cache_alloc(event_cachep, GFP_KERNEL);
if (unlikely(!kevent))
return NULL;
/* we hand this out to user-space, so zero it just in case */
memset(&kevent->event, 0, sizeof(struct inotify_event));
kevent->event.wd = wd;
kevent->event.mask = mask;
kevent->event.cookie = cookie;
INIT_LIST_HEAD(&kevent->list);
if (name) {
size_t len, rem, event_size = sizeof(struct inotify_event);
/*
* We need to pad the filename so as to properly align an
* array of inotify_event structures. Because the structure is
* small and the common case is a small filename, we just round
* up to the next multiple of the structure's sizeof. This is
* simple and safe for all architectures.
*/
len = strlen(name) + 1;
rem = event_size - len;
if (len > event_size) {
rem = event_size - (len % event_size);
if (len % event_size == 0)
rem = 0;
}
kevent->name = kmalloc(len + rem, GFP_KERNEL);
if (unlikely(!kevent->name)) {
kmem_cache_free(event_cachep, kevent);
return NULL;
}
memcpy(kevent->name, name, len);
if (rem)
memset(kevent->name + len, 0, rem);
kevent->event.len = len + rem;
} else {
kevent->event.len = 0;
kevent->name = NULL;
}
return kevent;
}
/*
* inotify_dev_get_event - return the next event in the given dev's queue
*
* Caller must hold dev->ev_mutex.
*/
static inline struct inotify_kernel_event *
inotify_dev_get_event(struct inotify_device *dev)
{
return list_entry(dev->events.next, struct inotify_kernel_event, list);
}
/*
* inotify_dev_queue_event - event handler registered with core inotify, adds
* a new event to the given device
*
* Can sleep (calls kernel_event()).
*/
static void inotify_dev_queue_event(struct inotify_watch *w, u32 wd, u32 mask,
u32 cookie, const char *name)
{
struct inotify_user_watch *watch;
struct inotify_device *dev;
struct inotify_kernel_event *kevent, *last;
watch = container_of(w, struct inotify_user_watch, wdata);
dev = watch->dev;
mutex_lock(&dev->ev_mutex);
/* we can safely put the watch as we don't reference it while
* generating the event
*/
if (mask & IN_IGNORED || mask & IN_ONESHOT)
put_inotify_watch(w); /* final put */
/* coalescing: drop this event if it is a dupe of the previous */
last = inotify_dev_get_event(dev);
if (last && last->event.mask == mask && last->event.wd == wd &&
last->event.cookie == cookie) {
const char *lastname = last->name;
if (!name && !lastname)
goto out;
if (name && lastname && !strcmp(lastname, name))
goto out;
}
/* the queue overflowed and we already sent the Q_OVERFLOW event */
if (unlikely(dev->event_count > dev->max_events))
goto out;
/* if the queue overflows, we need to notify user space */
if (unlikely(dev->event_count == dev->max_events))
kevent = kernel_event(-1, IN_Q_OVERFLOW, cookie, NULL);
else
kevent = kernel_event(wd, mask, cookie, name);
if (unlikely(!kevent))
goto out;
/* queue the event and wake up anyone waiting */
dev->event_count++;
dev->queue_size += sizeof(struct inotify_event) + kevent->event.len;
list_add_tail(&kevent->list, &dev->events);
wake_up_interruptible(&dev->wq);
out:
mutex_unlock(&dev->ev_mutex);
}
/*
* remove_kevent - cleans up and ultimately frees the given kevent
*
* Caller must hold dev->ev_mutex.
*/
static void remove_kevent(struct inotify_device *dev,
struct inotify_kernel_event *kevent)
{
list_del(&kevent->list);
dev->event_count--;
dev->queue_size -= sizeof(struct inotify_event) + kevent->event.len;
kfree(kevent->name);
kmem_cache_free(event_cachep, kevent);
}
/*
* inotify_dev_event_dequeue - destroy an event on the given device
*
* Caller must hold dev->ev_mutex.
*/
static void inotify_dev_event_dequeue(struct inotify_device *dev)
{
if (!list_empty(&dev->events)) {
struct inotify_kernel_event *kevent;
kevent = inotify_dev_get_event(dev);
remove_kevent(dev, kevent);
}
}
/*
* find_inode - resolve a user-given path to a specific inode and return a nd
*/
static int find_inode(const char __user *dirname, struct nameidata *nd,
unsigned flags)
{
int error;
error = __user_walk(dirname, flags, nd);
if (error)
return error;
/* you can only watch an inode if you have read permissions on it */
error = vfs_permission(nd, MAY_READ);
if (error)
path_release(nd);
return error;
}
/*
* create_watch - creates a watch on the given device.
*
* Callers must hold dev->up_mutex.
*/
static int create_watch(struct inotify_device *dev, struct inode *inode,
u32 mask)
{
struct inotify_user_watch *watch;
int ret;
if (atomic_read(&dev->user->inotify_watches) >=
inotify_max_user_watches)
return -ENOSPC;
watch = kmem_cache_alloc(watch_cachep, GFP_KERNEL);
if (unlikely(!watch))
return -ENOMEM;
/* save a reference to device and bump the count to make it official */
get_inotify_dev(dev);
watch->dev = dev;
atomic_inc(&dev->user->inotify_watches);
ret = inotify_add_watch(dev->ih, &watch->wdata, inode, mask);
if (ret < 0)
free_inotify_user_watch(&watch->wdata);
return ret;
}
/* Device Interface */
static unsigned int inotify_poll(struct file *file, poll_table *wait)
{
struct inotify_device *dev = file->private_data;
int ret = 0;
poll_wait(file, &dev->wq, wait);
mutex_lock(&dev->ev_mutex);
if (!list_empty(&dev->events))
ret = POLLIN | POLLRDNORM;
mutex_unlock(&dev->ev_mutex);
return ret;
}
static ssize_t inotify_read(struct file *file, char __user *buf,
size_t count, loff_t *pos)
{
size_t event_size = sizeof (struct inotify_event);
struct inotify_device *dev;
char __user *start;
int ret;
DEFINE_WAIT(wait);
start = buf;
dev = file->private_data;
while (1) {
int events;
prepare_to_wait(&dev->wq, &wait, TASK_INTERRUPTIBLE);
mutex_lock(&dev->ev_mutex);
events = !list_empty(&dev->events);
mutex_unlock(&dev->ev_mutex);
if (events) {
ret = 0;
break;
}
if (file->f_flags & O_NONBLOCK) {
ret = -EAGAIN;
break;
}
if (signal_pending(current)) {
ret = -EINTR;
break;
}
schedule();
}
finish_wait(&dev->wq, &wait);
if (ret)
return ret;
mutex_lock(&dev->ev_mutex);
while (1) {
struct inotify_kernel_event *kevent;
ret = buf - start;
if (list_empty(&dev->events))
break;
kevent = inotify_dev_get_event(dev);
if (event_size + kevent->event.len > count)
break;
if (copy_to_user(buf, &kevent->event, event_size)) {
ret = -EFAULT;
break;
}
buf += event_size;
count -= event_size;
if (kevent->name) {
if (copy_to_user(buf, kevent->name, kevent->event.len)){
ret = -EFAULT;
break;
}
buf += kevent->event.len;
count -= kevent->event.len;
}
remove_kevent(dev, kevent);
}
mutex_unlock(&dev->ev_mutex);
return ret;
}
static int inotify_release(struct inode *ignored, struct file *file)
{
struct inotify_device *dev = file->private_data;
inotify_destroy(dev->ih);
/* destroy all of the events on this device */
mutex_lock(&dev->ev_mutex);
while (!list_empty(&dev->events))
inotify_dev_event_dequeue(dev);
mutex_unlock(&dev->ev_mutex);
/* free this device: the put matching the get in inotify_init() */
put_inotify_dev(dev);
return 0;
}
static long inotify_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct inotify_device *dev;
void __user *p;
int ret = -ENOTTY;
dev = file->private_data;
p = (void __user *) arg;
switch (cmd) {
case FIONREAD:
ret = put_user(dev->queue_size, (int __user *) p);
break;
}
return ret;
}
static const struct file_operations inotify_fops = {
.poll = inotify_poll,
.read = inotify_read,
.release = inotify_release,
.unlocked_ioctl = inotify_ioctl,
.compat_ioctl = inotify_ioctl,
};
static const struct inotify_operations inotify_user_ops = {
.handle_event = inotify_dev_queue_event,
.destroy_watch = free_inotify_user_watch,
};
asmlinkage long sys_inotify_init(void)
{
struct inotify_device *dev;
struct inotify_handle *ih;
struct user_struct *user;
struct file *filp;
int fd, ret;
fd = get_unused_fd();
if (fd < 0)
return fd;
filp = get_empty_filp();
if (!filp) {
ret = -ENFILE;
goto out_put_fd;
}
user = get_uid(current->user);
if (unlikely(atomic_read(&user->inotify_devs) >=
inotify_max_user_instances)) {
ret = -EMFILE;
goto out_free_uid;
}
dev = kmalloc(sizeof(struct inotify_device), GFP_KERNEL);
if (unlikely(!dev)) {
ret = -ENOMEM;
goto out_free_uid;
}
ih = inotify_init(&inotify_user_ops);
if (unlikely(IS_ERR(ih))) {
ret = PTR_ERR(ih);
goto out_free_dev;
}
dev->ih = ih;
filp->f_op = &inotify_fops;
filp->f_vfsmnt = mntget(inotify_mnt);
filp->f_dentry = dget(inotify_mnt->mnt_root);
filp->f_mapping = filp->f_dentry->d_inode->i_mapping;
filp->f_mode = FMODE_READ;
filp->f_flags = O_RDONLY;
filp->private_data = dev;
INIT_LIST_HEAD(&dev->events);