[net-next-2.6.git] / fs / notify / fsnotify.c

/*
 *  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);

void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
{
	fsnotify_clear_marks_by_mount(mnt);
}

/*
 * 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 (!dentry)
		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);

void __fsnotify_flush_ignored_mask(struct inode *inode, void *data, int data_is)
{
	struct fsnotify_mark *mark;
	struct hlist_node *node;

	if (!hlist_empty(&inode->i_fsnotify_marks)) {
		spin_lock(&inode->i_lock);
		hlist_for_each_entry(mark, node, &inode->i_fsnotify_marks, i.i_list) {
			if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
				mark->ignored_mask = 0;
		}
		spin_unlock(&inode->i_lock);
	}

	if (data_is == FSNOTIFY_EVENT_FILE) {
		struct vfsmount *mnt;

		mnt = ((struct file *)data)->f_path.mnt;
		if (mnt && !hlist_empty(&mnt->mnt_fsnotify_marks)) {
			spin_lock(&mnt->mnt_root->d_lock);
			hlist_for_each_entry(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
				if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
					mark->ignored_mask = 0;
			}
			spin_unlock(&mnt->mnt_root->d_lock);
		}
	}
}

static int send_to_group(struct fsnotify_group *group, struct inode *to_tell,
			 struct vfsmount *mnt, __u32 mask, void *data,
			 int data_is, u32 cookie, const unsigned char *file_name,
			 struct fsnotify_event **event)
{
	pr_debug("%s: group=%p to_tell=%p mnt=%p mask=%x data=%p data_is=%d"
		 " cookie=%d event=%p\n", __func__, group, to_tell, mnt,
		 mask, data, data_is, cookie, *event);

	if (!group->ops->should_send_event(group, to_tell, mnt, mask,
					   data, data_is))
		return 0;
	if (!*event) {
		*event = fsnotify_create_event(to_tell, mask, data,
						data_is, file_name,
						cookie, GFP_KERNEL);
		if (!*event)
			return -ENOMEM;
	}
	return group->ops->handle_event(group, *event);
}

static bool needed_by_vfsmount(__u32 test_mask, struct vfsmount *mnt)
{
	if (!mnt)
		return false;

	return (test_mask & mnt->mnt_fsnotify_mask);
}

/*
 * 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.
 */
int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
	     const unsigned char *file_name, u32 cookie)
{
	struct fsnotify_group *group;
	struct fsnotify_event *event = NULL;
	struct vfsmount *mnt = NULL;
	int idx, ret = 0;
	/* 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 0;
 
	if (mask & FS_MODIFY)
		__fsnotify_flush_ignored_mask(to_tell, data, data_is);

	/* if none of the directed listeners or vfsmount listeners care */
	if (!(test_mask & fsnotify_inode_mask) &&
	    !(test_mask & fsnotify_vfsmount_mask))
		return 0;
 
	if (data_is == FSNOTIFY_EVENT_FILE)
		mnt = ((struct file *)data)->f_path.mnt;

	/* 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, mnt))
		return 0;

	/*
	 * 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) {
				ret = send_to_group(group, to_tell, NULL, mask, data, data_is,
						    cookie, file_name, &event);
				if (ret)
					goto out;
			}
		}
	}
	if (needed_by_vfsmount(test_mask, mnt)) {
		list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list) {
			if (test_mask & group->mask) {
				ret = send_to_group(group, to_tell, mnt, mask, data, data_is,
						    cookie, file_name, &event);
				if (ret)
					goto out;
			}
		}
	}
out:
	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);

	return ret;
}
EXPORT_SYMBOL_GPL(fsnotify);

static __init int fsnotify_init(void)
{
	BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);

	return init_srcu_struct(&fsnotify_grp_srcu);
}
subsys_initcall(fsnotify_init);
Commit	Line	Data
90586523 EP	1	/*
	2	* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2, or (at your option)
	7	* any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; see the file COPYING. If not, write to
	16	* the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
	17	*/
	18
	19	#include <linux/dcache.h>
	20	#include <linux/fs.h>
5a0e3ad6	21	#include <linux/gfp.h>
90586523 EP	22	#include <linux/init.h>
90586523 EP	23	#include <linux/module.h>
7131485a	24	#include <linux/mount.h>
90586523 EP	25	#include <linux/srcu.h>
	26
	27	#include <linux/fsnotify_backend.h>
	28	#include "fsnotify.h"
	29
3be25f49 EP	30	/*
	31	* Clear all of the marks on an inode when it is being evicted from core
	32	*/
	33	void __fsnotify_inode_delete(struct inode *inode)
	34	{
	35	fsnotify_clear_marks_by_inode(inode);
	36	}
	37	EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
	38
ca9c726e AG	39	void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
	40	{
	41	fsnotify_clear_marks_by_mount(mnt);
	42	}
	43
c28f7e56 EP	44	/*
	45	* Given an inode, first check if we care what happens to our children. Inotify
	46	* and dnotify both tell their parents about events. If we care about any event
	47	* on a child we run all of our children and set a dentry flag saying that the
	48	* parent cares. Thus when an event happens on a child it can quickly tell if
	49	* if there is a need to find a parent and send the event to the parent.
	50	*/
	51	void __fsnotify_update_child_dentry_flags(struct inode *inode)
	52	{
	53	struct dentry *alias;
	54	int watched;
	55
	56	if (!S_ISDIR(inode->i_mode))
	57	return;
	58
	59	/* determine if the children should tell inode about their events */
	60	watched = fsnotify_inode_watches_children(inode);
	61
	62	spin_lock(&dcache_lock);
	63	/* run all of the dentries associated with this inode. Since this is a
	64	* directory, there damn well better only be one item on this list */
	65	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
	66	struct dentry *child;
	67
	68	/* run all of the children of the original inode and fix their
	69	* d_flags to indicate parental interest (their parent is the
	70	* original inode) */
	71	list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
	72	if (!child->d_inode)
	73	continue;
	74
	75	spin_lock(&child->d_lock);
	76	if (watched)
	77	child->d_flags \|= DCACHE_FSNOTIFY_PARENT_WATCHED;
	78	else
	79	child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
	80	spin_unlock(&child->d_lock);
	81	}
	82	}
	83	spin_unlock(&dcache_lock);
	84	}
	85
	86	/* Notify this dentry's parent about a child's events. */
3bcf3860	87	void __fsnotify_parent(struct file file, struct dentry dentry, __u32 mask)
c28f7e56 EP	88	{
	89	struct dentry *parent;
	90	struct inode *p_inode;
	91	bool send = false;
	92	bool should_update_children = false;
	93
72acc854	94	if (!dentry)
3bcf3860	95	dentry = file->f_path.dentry;
28c60e37	96
c28f7e56 EP	97	if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
	98	return;
	99
	100	spin_lock(&dentry->d_lock);
	101	parent = dentry->d_parent;
	102	p_inode = parent->d_inode;
	103
	104	if (fsnotify_inode_watches_children(p_inode)) {
	105	if (p_inode->i_fsnotify_mask & mask) {
	106	dget(parent);
	107	send = true;
	108	}
	109	} else {
	110	/*
	111	* The parent doesn't care about events on it's children but
	112	* at least one child thought it did. We need to run all the
	113	* children and update their d_flags to let them know p_inode
	114	* doesn't care about them any more.
	115	*/
	116	dget(parent);
	117	should_update_children = true;
	118	}
	119
	120	spin_unlock(&dentry->d_lock);
	121
	122	if (send) {
	123	/* we are notifying a parent so come up with the new mask which
	124	* specifies these are events which came from a child. */
	125	mask \|= FS_EVENT_ON_CHILD;
	126
3bcf3860 EP	127	if (file)
3bcf3860 EP	128	fsnotify(p_inode, mask, file, FSNOTIFY_EVENT_FILE,
28c60e37 EP	129	dentry->d_name.name, 0);
	130	else
	131	fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
	132	dentry->d_name.name, 0);
c28f7e56 EP	133	dput(parent);
	134	}
	135
	136	if (unlikely(should_update_children)) {
	137	__fsnotify_update_child_dentry_flags(p_inode);
	138	dput(parent);
	139	}
	140	}
	141	EXPORT_SYMBOL_GPL(__fsnotify_parent);
	142
e8983861 EP	143	void __fsnotify_flush_ignored_mask(struct inode inode, void data, int data_is)
	144	{
	145	struct fsnotify_mark *mark;
	146	struct hlist_node *node;
	147
	148	if (!hlist_empty(&inode->i_fsnotify_marks)) {
	149	spin_lock(&inode->i_lock);
	150	hlist_for_each_entry(mark, node, &inode->i_fsnotify_marks, i.i_list) {
c908370f EP	151	if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
c908370f EP	152	mark->ignored_mask = 0;
e8983861 EP	153	}
	154	spin_unlock(&inode->i_lock);
	155	}
	156
3bcf3860	157	if (data_is == FSNOTIFY_EVENT_FILE) {
e8983861 EP	158	struct vfsmount *mnt;
e8983861 EP	159
3bcf3860	160	mnt = ((struct file *)data)->f_path.mnt;
e8983861 EP	161	if (mnt && !hlist_empty(&mnt->mnt_fsnotify_marks)) {
	162	spin_lock(&mnt->mnt_root->d_lock);
	163	hlist_for_each_entry(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
c908370f EP	164	if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
c908370f EP	165	mark->ignored_mask = 0;
e8983861 EP	166	}
	167	spin_unlock(&mnt->mnt_root->d_lock);
	168	}
	169	}
	170	}
	171
c4ec54b4 EP	172	static int send_to_group(struct fsnotify_group group, struct inode to_tell,
	173	struct vfsmount mnt, __u32 mask, void data,
	174	int data_is, u32 cookie, const unsigned char *file_name,
	175	struct fsnotify_event **event)
7131485a	176	{
5ba08e2e EP	177	pr_debug("%s: group=%p to_tell=%p mnt=%p mask=%x data=%p data_is=%d"
	178	" cookie=%d event=%p\n", __func__, group, to_tell, mnt,
	179	mask, data, data_is, cookie, *event);
	180
3a9fb89f	181	if (!group->ops->should_send_event(group, to_tell, mnt, mask,
7131485a	182	data, data_is))
c4ec54b4	183	return 0;
7131485a EP	184	if (!*event) {
	185	*event = fsnotify_create_event(to_tell, mask, data,
	186	data_is, file_name,
	187	cookie, GFP_KERNEL);
7131485a	188	if (!*event)
c4ec54b4	189	return -ENOMEM;
7131485a	190	}
c4ec54b4	191	return group->ops->handle_event(group, *event);
7131485a EP	192	}
7131485a EP	193
3a9fb89f	194	static bool needed_by_vfsmount(__u32 test_mask, struct vfsmount *mnt)
7131485a	195	{
3a9fb89f	196	if (!mnt)
7131485a EP	197	return false;
7131485a EP	198
2504c5d6	199	return (test_mask & mnt->mnt_fsnotify_mask);
7131485a	200	}
e8983861	201
90586523 EP	202	/*
	203	* This is the main call to fsnotify. The VFS calls into hook specific functions
	204	* in linux/fsnotify.h. Those functions then in turn call here. Here will call
	205	* out to all of the registered fsnotify_group. Those groups can then use the
	206	* notification event in whatever means they feel necessary.
	207	*/
c4ec54b4 EP	208	int fsnotify(struct inode to_tell, __u32 mask, void data, int data_is,
c4ec54b4 EP	209	const unsigned char *file_name, u32 cookie)
90586523 EP	210	{
	211	struct fsnotify_group *group;
	212	struct fsnotify_event *event = NULL;
3a9fb89f	213	struct vfsmount *mnt = NULL;
c4ec54b4	214	int idx, ret = 0;
e42e2773 EP	215	/* global tests shouldn't care about events on child only the specific event */
e42e2773 EP	216	__u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
90586523	217
7131485a EP	218	/* if no fsnotify listeners, nothing to do */
	219	if (list_empty(&fsnotify_inode_groups) &&
	220	list_empty(&fsnotify_vfsmount_groups))
c4ec54b4	221	return 0;
7131485a	222
e8983861 EP	223	if (mask & FS_MODIFY)
	224	__fsnotify_flush_ignored_mask(to_tell, data, data_is);
	225
7131485a EP	226	/* if none of the directed listeners or vfsmount listeners care */
	227	if (!(test_mask & fsnotify_inode_mask) &&
	228	!(test_mask & fsnotify_vfsmount_mask))
c4ec54b4	229	return 0;
7131485a	230
3bcf3860 EP	231	if (data_is == FSNOTIFY_EVENT_FILE)
3bcf3860 EP	232	mnt = ((struct file *)data)->f_path.mnt;
3a9fb89f	233
7131485a EP	234	/* if this inode's directed listeners don't care and nothing on the vfsmount
	235	* listeners list cares, nothing to do */
	236	if (!(test_mask & to_tell->i_fsnotify_mask) &&
3a9fb89f	237	!needed_by_vfsmount(test_mask, mnt))
c4ec54b4	238	return 0;
90586523	239
90586523 EP	240	/*
	241	* SRCU!! the groups list is very very much read only and the path is
	242	* very hot. The VAST majority of events are not going to need to do
	243	* anything other than walk the list so it's crazy to pre-allocate.
	244	*/
	245	idx = srcu_read_lock(&fsnotify_grp_srcu);
7131485a EP	246
	247	if (test_mask & to_tell->i_fsnotify_mask) {
	248	list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list) {
	249	if (test_mask & group->mask) {
c4ec54b4 EP	250	ret = send_to_group(group, to_tell, NULL, mask, data, data_is,
	251	cookie, file_name, &event);
	252	if (ret)
	253	goto out;
90586523	254	}
90586523 EP	255	}
90586523 EP	256	}
3a9fb89f	257	if (needed_by_vfsmount(test_mask, mnt)) {
7131485a EP	258	list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list) {
7131485a EP	259	if (test_mask & group->mask) {
c4ec54b4 EP	260	ret = send_to_group(group, to_tell, mnt, mask, data, data_is,
	261	cookie, file_name, &event);
	262	if (ret)
	263	goto out;
7131485a EP	264	}
	265	}
	266	}
c4ec54b4	267	out:
90586523 EP	268	srcu_read_unlock(&fsnotify_grp_srcu, idx);
	269	/*
	270	* fsnotify_create_event() took a reference so the event can't be cleaned
	271	* up while we are still trying to add it to lists, drop that one.
	272	*/
	273	if (event)
	274	fsnotify_put_event(event);
c4ec54b4	275
98b5c10d	276	return ret;
90586523 EP	277	}
	278	EXPORT_SYMBOL_GPL(fsnotify);
	279
	280	static __init int fsnotify_init(void)
	281	{
20dee624 EP	282	BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
20dee624 EP	283
90586523 EP	284	return init_srcu_struct(&fsnotify_grp_srcu);
	285	}
	286	subsys_initcall(fsnotify_init);