[linux.git] / fs / dnotify.c

/*
 * Directory notifications for Linux.
 *
 * Copyright (C) 2000,2001,2002 Stephen Rothwell
 *
 * 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/fs.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/dnotify.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/fdtable.h>

int dir_notify_enable __read_mostly = 1;

static struct kmem_cache *dn_cache __read_mostly;

static void redo_inode_mask(struct inode *inode)
{
	unsigned long new_mask;
	struct dnotify_struct *dn;

	new_mask = 0;
	for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next)
		new_mask |= dn->dn_mask & ~DN_MULTISHOT;
	inode->i_dnotify_mask = new_mask;
}

void dnotify_flush(struct file *filp, fl_owner_t id)
{
	struct dnotify_struct *dn;
	struct dnotify_struct **prev;
	struct inode *inode;

	inode = filp->f_path.dentry->d_inode;
	if (!S_ISDIR(inode->i_mode))
		return;
	spin_lock(&inode->i_lock);
	prev = &inode->i_dnotify;
	while ((dn = *prev) != NULL) {
		if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
			*prev = dn->dn_next;
			redo_inode_mask(inode);
			kmem_cache_free(dn_cache, dn);
			break;
		}
		prev = &dn->dn_next;
	}
	spin_unlock(&inode->i_lock);
}

int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
{
	struct dnotify_struct *dn;
	struct dnotify_struct *odn;
	struct dnotify_struct **prev;
	struct inode *inode;
	fl_owner_t id = current->files;
	struct file *f;
	int error = 0;

	if ((arg & ~DN_MULTISHOT) == 0) {
		dnotify_flush(filp, id);
		return 0;
	}
	if (!dir_notify_enable)
		return -EINVAL;
	inode = filp->f_path.dentry->d_inode;
	if (!S_ISDIR(inode->i_mode))
		return -ENOTDIR;
	dn = kmem_cache_alloc(dn_cache, GFP_KERNEL);
	if (dn == NULL)
		return -ENOMEM;
	spin_lock(&inode->i_lock);
	prev = &inode->i_dnotify;
	while ((odn = *prev) != NULL) {
		if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
			odn->dn_fd = fd;
			odn->dn_mask |= arg;
			inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
			goto out_free;
		}
		prev = &odn->dn_next;
	}

	rcu_read_lock();
	f = fcheck(fd);
	rcu_read_unlock();
	/* we'd lost the race with close(), sod off silently */
	/* note that inode->i_lock prevents reordering problems
	 * between accesses to descriptor table and ->i_dnotify */
	if (f != filp)
		goto out_free;

	error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
	if (error)
		goto out_free;

	dn->dn_mask = arg;
	dn->dn_fd = fd;
	dn->dn_filp = filp;
	dn->dn_owner = id;
	inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
	dn->dn_next = inode->i_dnotify;
	inode->i_dnotify = dn;
	spin_unlock(&inode->i_lock);

	if (filp->f_op && filp->f_op->dir_notify)
		return filp->f_op->dir_notify(filp, arg);
	return 0;

out_free:
	spin_unlock(&inode->i_lock);
	kmem_cache_free(dn_cache, dn);
	return error;
}

void __inode_dir_notify(struct inode *inode, unsigned long event)
{
	struct dnotify_struct *	dn;
	struct dnotify_struct **prev;
	struct fown_struct *	fown;
	int			changed = 0;

	spin_lock(&inode->i_lock);
	prev = &inode->i_dnotify;
	while ((dn = *prev) != NULL) {
		if ((dn->dn_mask & event) == 0) {
			prev = &dn->dn_next;
			continue;
		}
		fown = &dn->dn_filp->f_owner;
		send_sigio(fown, dn->dn_fd, POLL_MSG);
		if (dn->dn_mask & DN_MULTISHOT)
			prev = &dn->dn_next;
		else {
			*prev = dn->dn_next;
			changed = 1;
			kmem_cache_free(dn_cache, dn);
		}
	}
	if (changed)
		redo_inode_mask(inode);
	spin_unlock(&inode->i_lock);
}

EXPORT_SYMBOL(__inode_dir_notify);

/*
 * This is hopelessly wrong, but unfixable without API changes.  At
 * least it doesn't oops the kernel...
 *
 * To safely access ->d_parent we need to keep d_move away from it.  Use the
 * dentry's d_lock for this.
 */
void dnotify_parent(struct dentry *dentry, unsigned long event)
{
	struct dentry *parent;

	if (!dir_notify_enable)
		return;

	spin_lock(&dentry->d_lock);
	parent = dentry->d_parent;
	if (parent->d_inode->i_dnotify_mask & event) {
		dget(parent);
		spin_unlock(&dentry->d_lock);
		__inode_dir_notify(parent->d_inode, event);
		dput(parent);
	} else {
		spin_unlock(&dentry->d_lock);
	}
}
EXPORT_SYMBOL_GPL(dnotify_parent);

static int __init dnotify_init(void)
{
	dn_cache = kmem_cache_create("dnotify_cache",
		sizeof(struct dnotify_struct), 0, SLAB_PANIC, NULL);
	return 0;
}

module_init(dnotify_init)
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Directory notifications for Linux.
	3	*
	4	* Copyright (C) 2000,2001,2002 Stephen Rothwell
	5	*
	6	* This program is free software; you can redistribute it and/or modify it
	7	* under the terms of the GNU General Public License as published by the
	8	* Free Software Foundation; either version 2, or (at your option) any
	9	* later version.
	10	*
	11	* This program is distributed in the hope that it will be useful, but
	12	* WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	14	* General Public License for more details.
	15	*/
	16	#include <linux/fs.h>
	17	#include <linux/module.h>
	18	#include <linux/sched.h>
	19	#include <linux/dnotify.h>
	20	#include <linux/init.h>
	21	#include <linux/spinlock.h>
	22	#include <linux/slab.h>
9f3acc31	23	#include <linux/fdtable.h>
1da177e4	24
fa3536cc	25	int dir_notify_enable __read_mostly = 1;
1da177e4	26
e18b890b	27	static struct kmem_cache *dn_cache __read_mostly;
1da177e4 LT	28
	29	static void redo_inode_mask(struct inode *inode)
	30	{
	31	unsigned long new_mask;
	32	struct dnotify_struct *dn;
	33
	34	new_mask = 0;
	35	for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next)
	36	new_mask \|= dn->dn_mask & ~DN_MULTISHOT;
	37	inode->i_dnotify_mask = new_mask;
	38	}
	39
	40	void dnotify_flush(struct file *filp, fl_owner_t id)
	41	{
	42	struct dnotify_struct *dn;
	43	struct dnotify_struct **prev;
	44	struct inode *inode;
	45
0f7fc9e4	46	inode = filp->f_path.dentry->d_inode;
1da177e4 LT	47	if (!S_ISDIR(inode->i_mode))
	48	return;
	49	spin_lock(&inode->i_lock);
	50	prev = &inode->i_dnotify;
	51	while ((dn = *prev) != NULL) {
	52	if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
	53	*prev = dn->dn_next;
	54	redo_inode_mask(inode);
	55	kmem_cache_free(dn_cache, dn);
	56	break;
	57	}
	58	prev = &dn->dn_next;
	59	}
	60	spin_unlock(&inode->i_lock);
	61	}
	62
	63	int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
	64	{
	65	struct dnotify_struct *dn;
	66	struct dnotify_struct *odn;
	67	struct dnotify_struct **prev;
	68	struct inode *inode;
	69	fl_owner_t id = current->files;
214b7049	70	struct file *f;
1da177e4 LT	71	int error = 0;
	72
	73	if ((arg & ~DN_MULTISHOT) == 0) {
	74	dnotify_flush(filp, id);
	75	return 0;
	76	}
	77	if (!dir_notify_enable)
	78	return -EINVAL;
0f7fc9e4	79	inode = filp->f_path.dentry->d_inode;
1da177e4 LT	80	if (!S_ISDIR(inode->i_mode))
1da177e4 LT	81	return -ENOTDIR;
e94b1766	82	dn = kmem_cache_alloc(dn_cache, GFP_KERNEL);
1da177e4 LT	83	if (dn == NULL)
	84	return -ENOMEM;
	85	spin_lock(&inode->i_lock);
	86	prev = &inode->i_dnotify;
	87	while ((odn = *prev) != NULL) {
	88	if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
	89	odn->dn_fd = fd;
	90	odn->dn_mask \|= arg;
	91	inode->i_dnotify_mask \|= arg & ~DN_MULTISHOT;
	92	goto out_free;
	93	}
	94	prev = &odn->dn_next;
	95	}
	96
214b7049 AV	97	rcu_read_lock();
	98	f = fcheck(fd);
	99	rcu_read_unlock();
	100	/* we'd lost the race with close(), sod off silently */
	101	/* note that inode->i_lock prevents reordering problems
	102	* between accesses to descriptor table and ->i_dnotify */
	103	if (f != filp)
	104	goto out_free;
	105
609d7fa9	106	error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
1da177e4 LT	107	if (error)
	108	goto out_free;
	109
	110	dn->dn_mask = arg;
	111	dn->dn_fd = fd;
	112	dn->dn_filp = filp;
	113	dn->dn_owner = id;
	114	inode->i_dnotify_mask \|= arg & ~DN_MULTISHOT;
	115	dn->dn_next = inode->i_dnotify;
	116	inode->i_dnotify = dn;
	117	spin_unlock(&inode->i_lock);
	118
	119	if (filp->f_op && filp->f_op->dir_notify)
	120	return filp->f_op->dir_notify(filp, arg);
	121	return 0;
	122
	123	out_free:
	124	spin_unlock(&inode->i_lock);
	125	kmem_cache_free(dn_cache, dn);
	126	return error;
	127	}
	128
	129	void __inode_dir_notify(struct inode *inode, unsigned long event)
	130	{
	131	struct dnotify_struct * dn;
	132	struct dnotify_struct **prev;
	133	struct fown_struct * fown;
	134	int changed = 0;
	135
	136	spin_lock(&inode->i_lock);
	137	prev = &inode->i_dnotify;
	138	while ((dn = *prev) != NULL) {
	139	if ((dn->dn_mask & event) == 0) {
	140	prev = &dn->dn_next;
	141	continue;
	142	}
	143	fown = &dn->dn_filp->f_owner;
	144	send_sigio(fown, dn->dn_fd, POLL_MSG);
	145	if (dn->dn_mask & DN_MULTISHOT)
	146	prev = &dn->dn_next;
	147	else {
	148	*prev = dn->dn_next;
	149	changed = 1;
	150	kmem_cache_free(dn_cache, dn);
	151	}
	152	}
	153	if (changed)
	154	redo_inode_mask(inode);
	155	spin_unlock(&inode->i_lock);
	156	}
	157
	158	EXPORT_SYMBOL(__inode_dir_notify);
	159
	160	/*
	161	* This is hopelessly wrong, but unfixable without API changes. At
	162	* least it doesn't oops the kernel...
	163	*
	164	* To safely access ->d_parent we need to keep d_move away from it. Use the
	165	* dentry's d_lock for this.
	166	*/
	167	void dnotify_parent(struct dentry *dentry, unsigned long event)
	168	{
	169	struct dentry *parent;
	170
171	if (!dir_notify_enable)
172	return;
173
174	spin_lock(&dentry->d_lock);
175	parent = dentry->d_parent;
176	if (parent->d_inode->i_dnotify_mask & event) {
177	dget(parent);
178	spin_unlock(&dentry->d_lock);
179	__inode_dir_notify(parent->d_inode, event);
180	dput(parent);
181	} else {
182	spin_unlock(&dentry->d_lock);
183	}
184	}
185	EXPORT_SYMBOL_GPL(dnotify_parent);
186
187	static int __init dnotify_init(void)
188	{
189	dn_cache = kmem_cache_create("dnotify_cache",
20c2df83	190	sizeof(struct dnotify_struct), 0, SLAB_PANIC, NULL);
1da177e4 LT	191	return 0;
	192	}
	193
	194	module_init(dnotify_init)