fs/notify/fsnotify.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
  */

 #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);
 }

 /**
  * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
  * @sb: superblock being unmounted.
  *
  * Called during unmount with no locks held, so needs to be safe against
  * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
  */
 static void fsnotify_unmount_inodes(struct super_block *sb)
 {
 	struct inode *inode, *iput_inode = NULL;

 	spin_lock(&sb->s_inode_list_lock);
 	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
 		/*
 		 * We cannot __iget() an inode in state I_FREEING,
 		 * I_WILL_FREE, or I_NEW which is fine because by that point
 		 * the inode cannot have any associated watches.
 		 */
 		spin_lock(&inode->i_lock);
 		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
 			spin_unlock(&inode->i_lock);
 			continue;
 		}

 		/*
 		 * If i_count is zero, the inode cannot have any watches and
 		 * doing an __iget/iput with SB_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.
 		 * However, we should have been called /after/ evict_inodes
 		 * removed all zero refcount inodes, in any case.  Test to
 		 * be sure.
 		 */
 		if (!atomic_read(&inode->i_count)) {
 			spin_unlock(&inode->i_lock);
 			continue;
 		}

 		__iget(inode);
 		spin_unlock(&inode->i_lock);
 		spin_unlock(&sb->s_inode_list_lock);

 		if (iput_inode)
 			iput(iput_inode);

 		/* for each watch, send FS_UNMOUNT and then remove it */
 		fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);

 		fsnotify_inode_delete(inode);

 		iput_inode = inode;

 		cond_resched();
 		spin_lock(&sb->s_inode_list_lock);
 	}
 	spin_unlock(&sb->s_inode_list_lock);

 	if (iput_inode)
 		iput(iput_inode);
 	/* Wait for outstanding inode references from connectors */
 	wait_var_event(&sb->s_fsnotify_inode_refs,
 		       !atomic_long_read(&sb->s_fsnotify_inode_refs));
 }

 void fsnotify_sb_delete(struct super_block *sb)
 {
 	fsnotify_unmount_inodes(sb);
 	fsnotify_clear_marks_by_sb(sb);
 }

 /*
  * 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(&inode->i_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 */
 	hlist_for_each_entry(alias, &inode->i_dentry, d_u.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) */
 		spin_lock(&alias->d_lock);
 		list_for_each_entry(child, &alias->d_subdirs, d_child) {
 			if (!child->d_inode)
 				continue;

 			spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
 			if (watched)
 				child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
 			else
 				child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
 			spin_unlock(&child->d_lock);
 		}
 		spin_unlock(&alias->d_lock);
 	}
 	spin_unlock(&inode->i_lock);
 }

 /* Notify this dentry's parent about a child's events. */
 int __fsnotify_parent(const struct path *path, struct dentry *dentry, __u32 mask)
 {
 	struct dentry *parent;
 	struct inode *p_inode;
 	int ret = 0;

 	if (!dentry)
 		dentry = path->dentry;

 	if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
 		return 0;

 	parent = dget_parent(dentry);
 	p_inode = parent->d_inode;

 	if (unlikely(!fsnotify_inode_watches_children(p_inode))) {
 		__fsnotify_update_child_dentry_flags(p_inode);
 	} else if (p_inode->i_fsnotify_mask & mask & ALL_FSNOTIFY_EVENTS) {
 		struct name_snapshot name;

 		/* 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;

 		take_dentry_name_snapshot(&name, dentry);
 		if (path)
 			ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
 				       &name.name, 0);
 		else
 			ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
 				       &name.name, 0);
 		release_dentry_name_snapshot(&name);
 	}

 	dput(parent);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(__fsnotify_parent);

 static int send_to_group(struct inode *to_tell,
 			 __u32 mask, const void *data,
 			 int data_is, u32 cookie,
 			 const struct qstr *file_name,
 			 struct fsnotify_iter_info *iter_info)
 {
 	struct fsnotify_group *group = NULL;
 	__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
 	__u32 marks_mask = 0;
 	__u32 marks_ignored_mask = 0;
 	struct fsnotify_mark *mark;
 	int type;

 	if (WARN_ON(!iter_info->report_mask))
 		return 0;

 	/* clear ignored on inode modification */
 	if (mask & FS_MODIFY) {
 		fsnotify_foreach_obj_type(type) {
 			if (!fsnotify_iter_should_report_type(iter_info, type))
 				continue;
 			mark = iter_info->marks[type];
 			if (mark &&
 			    !(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 				mark->ignored_mask = 0;
 		}
 	}

 	fsnotify_foreach_obj_type(type) {
 		if (!fsnotify_iter_should_report_type(iter_info, type))
 			continue;
 		mark = iter_info->marks[type];
 		/* does the object mark tell us to do something? */
 		if (mark) {
 			group = mark->group;
 			marks_mask |= mark->mask;
 			marks_ignored_mask |= mark->ignored_mask;
 		}
 	}

 	pr_debug("%s: group=%p to_tell=%p mask=%x marks_mask=%x marks_ignored_mask=%x"
 		 " data=%p data_is=%d cookie=%d\n",
 		 __func__, group, to_tell, mask, marks_mask, marks_ignored_mask,
 		 data, data_is, cookie);

 	if (!(test_mask & marks_mask & ~marks_ignored_mask))
 		return 0;

 	return group->ops->handle_event(group, to_tell, mask, data, data_is,
 					file_name, cookie, iter_info);
 }

 static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
 {
 	struct fsnotify_mark_connector *conn;
 	struct hlist_node *node = NULL;

 	conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
 	if (conn)
 		node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);

 	return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
 }

 static struct fsnotify_mark *fsnotify_next_mark(struct fsnotify_mark *mark)
 {
 	struct hlist_node *node = NULL;

 	if (mark)
 		node = srcu_dereference(mark->obj_list.next,
 					&fsnotify_mark_srcu);

 	return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
 }

 /*
  * iter_info is a multi head priority queue of marks.
  * Pick a subset of marks from queue heads, all with the
  * same group and set the report_mask for selected subset.
  * Returns the report_mask of the selected subset.
  */
 static unsigned int fsnotify_iter_select_report_types(
 		struct fsnotify_iter_info *iter_info)
 {
 	struct fsnotify_group *max_prio_group = NULL;
 	struct fsnotify_mark *mark;
 	int type;

 	/* Choose max prio group among groups of all queue heads */
 	fsnotify_foreach_obj_type(type) {
 		mark = iter_info->marks[type];
 		if (mark &&
 		    fsnotify_compare_groups(max_prio_group, mark->group) > 0)
 			max_prio_group = mark->group;
 	}

 	if (!max_prio_group)
 		return 0;

 	/* Set the report mask for marks from same group as max prio group */
 	iter_info->report_mask = 0;
 	fsnotify_foreach_obj_type(type) {
 		mark = iter_info->marks[type];
 		if (mark &&
 		    fsnotify_compare_groups(max_prio_group, mark->group) == 0)
 			fsnotify_iter_set_report_type(iter_info, type);
 	}

 	return iter_info->report_mask;
 }

 /*
  * Pop from iter_info multi head queue, the marks that were iterated in the
  * current iteration step.
  */
 static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
 {
 	int type;

 	fsnotify_foreach_obj_type(type) {
 		if (fsnotify_iter_should_report_type(iter_info, type))
 			iter_info->marks[type] =
 				fsnotify_next_mark(iter_info->marks[type]);
 	}
 }

 /*
  * 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, const void *data, int data_is,
 	     const struct qstr *file_name, u32 cookie)
 {
 	struct fsnotify_iter_info iter_info = {};
 	struct super_block *sb = to_tell->i_sb;
 	struct mount *mnt = NULL;
 	__u32 mnt_or_sb_mask = sb->s_fsnotify_mask;
 	int ret = 0;
 	__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);

 	if (data_is == FSNOTIFY_EVENT_PATH) {
 		mnt = real_mount(((const struct path *)data)->mnt);
 		mnt_or_sb_mask |= mnt->mnt_fsnotify_mask;
 	}
 	/* An event "on child" is not intended for a mount/sb mark */
 	if (mask & FS_EVENT_ON_CHILD)
 		mnt_or_sb_mask = 0;

 	/*
 	 * Optimization: srcu_read_lock() has a memory barrier which can
 	 * be expensive.  It protects walking the *_fsnotify_marks lists.
 	 * However, if we do not walk the lists, we do not have to do
 	 * SRCU because we have no references to any objects and do not
 	 * need SRCU to keep them "alive".
 	 */
 	if (!to_tell->i_fsnotify_marks && !sb->s_fsnotify_marks &&
 	    (!mnt || !mnt->mnt_fsnotify_marks))
 		return 0;
 	/*
 	 * if this is a modify event we may need to clear the ignored masks
 	 * otherwise return if neither the inode nor the vfsmount/sb care about
 	 * this type of event.
 	 */
 	if (!(mask & FS_MODIFY) &&
 	    !(test_mask & (to_tell->i_fsnotify_mask | mnt_or_sb_mask)))
 		return 0;

 	iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);

 	iter_info.marks[FSNOTIFY_OBJ_TYPE_INODE] =
 		fsnotify_first_mark(&to_tell->i_fsnotify_marks);
 	iter_info.marks[FSNOTIFY_OBJ_TYPE_SB] =
 		fsnotify_first_mark(&sb->s_fsnotify_marks);
 	if (mnt) {
 		iter_info.marks[FSNOTIFY_OBJ_TYPE_VFSMOUNT] =
 			fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
 	}

 	/*
 	 * We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
 	 * ignore masks are properly reflected for mount/sb mark notifications.
 	 * That's why this traversal is so complicated...
 	 */
 	while (fsnotify_iter_select_report_types(&iter_info)) {
 		ret = send_to_group(to_tell, mask, data, data_is, cookie,
 				    file_name, &iter_info);

 		if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
 			goto out;

 		fsnotify_iter_next(&iter_info);
 	}
 	ret = 0;
 out:
 	srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(fsnotify);

 extern struct kmem_cache *fsnotify_mark_connector_cachep;

 static __init int fsnotify_init(void)
 {
 	int ret;

 	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);

 	ret = init_srcu_struct(&fsnotify_mark_srcu);
 	if (ret)
 		panic("initializing fsnotify_mark_srcu");

 	fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
 						    SLAB_PANIC);

 	return 0;
 }
 core_initcall(fsnotify_init);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
	*/

	#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);
	}

	/**
	* fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
	* @sb: superblock being unmounted.
	*
	* Called during unmount with no locks held, so needs to be safe against
	* concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
	*/
	static void fsnotify_unmount_inodes(struct super_block *sb)
	{
	struct inode inode, iput_inode = NULL;

	spin_lock(&sb->s_inode_list_lock);
	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
	/*
	* We cannot __iget() an inode in state I_FREEING,
	* I_WILL_FREE, or I_NEW which is fine because by that point
	* the inode cannot have any associated watches.
	*/
	spin_lock(&inode->i_lock);
	if (inode->i_state & (I_FREEING\|I_WILL_FREE\|I_NEW)) {
	spin_unlock(&inode->i_lock);
	continue;
	}

	/*
	* If i_count is zero, the inode cannot have any watches and
	* doing an __iget/iput with SB_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.
	* However, we should have been called /after/ evict_inodes
	* removed all zero refcount inodes, in any case. Test to
	* be sure.
	*/
	if (!atomic_read(&inode->i_count)) {
	spin_unlock(&inode->i_lock);
	continue;
	}

	__iget(inode);
	spin_unlock(&inode->i_lock);
	spin_unlock(&sb->s_inode_list_lock);

	if (iput_inode)
	iput(iput_inode);

	/* for each watch, send FS_UNMOUNT and then remove it */
	fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);

	fsnotify_inode_delete(inode);

	iput_inode = inode;

	cond_resched();
	spin_lock(&sb->s_inode_list_lock);
	}
	spin_unlock(&sb->s_inode_list_lock);

	if (iput_inode)
	iput(iput_inode);
	/* Wait for outstanding inode references from connectors */
	wait_var_event(&sb->s_fsnotify_inode_refs,
	!atomic_long_read(&sb->s_fsnotify_inode_refs));
	}

	void fsnotify_sb_delete(struct super_block *sb)
	{
	fsnotify_unmount_inodes(sb);
	fsnotify_clear_marks_by_sb(sb);
	}

	/*
	* 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(&inode->i_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 */
	hlist_for_each_entry(alias, &inode->i_dentry, d_u.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) */
	spin_lock(&alias->d_lock);
	list_for_each_entry(child, &alias->d_subdirs, d_child) {
	if (!child->d_inode)
	continue;

	spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
	if (watched)
	child->d_flags \|= DCACHE_FSNOTIFY_PARENT_WATCHED;
	else
	child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
	spin_unlock(&child->d_lock);
	}
	spin_unlock(&alias->d_lock);
	}
	spin_unlock(&inode->i_lock);
	}

	/* Notify this dentry's parent about a child's events. */
	int __fsnotify_parent(const struct path path, struct dentry dentry, __u32 mask)
	{
	struct dentry *parent;
	struct inode *p_inode;
	int ret = 0;

	if (!dentry)
	dentry = path->dentry;

	if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
	return 0;

	parent = dget_parent(dentry);
	p_inode = parent->d_inode;

	if (unlikely(!fsnotify_inode_watches_children(p_inode))) {
	__fsnotify_update_child_dentry_flags(p_inode);
	} else if (p_inode->i_fsnotify_mask & mask & ALL_FSNOTIFY_EVENTS) {
	struct name_snapshot name;

	/* 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;

	take_dentry_name_snapshot(&name, dentry);
	if (path)
	ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
	&name.name, 0);
	else
	ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
	&name.name, 0);
	release_dentry_name_snapshot(&name);
	}

	dput(parent);

	return ret;
	}
	EXPORT_SYMBOL_GPL(__fsnotify_parent);

	static int send_to_group(struct inode *to_tell,
	__u32 mask, const void *data,
	int data_is, u32 cookie,
	const struct qstr *file_name,
	struct fsnotify_iter_info *iter_info)
	{
	struct fsnotify_group *group = NULL;
	__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);
	__u32 marks_mask = 0;
	__u32 marks_ignored_mask = 0;
	struct fsnotify_mark *mark;
	int type;

	if (WARN_ON(!iter_info->report_mask))
	return 0;

	/* clear ignored on inode modification */
	if (mask & FS_MODIFY) {
	fsnotify_foreach_obj_type(type) {
	if (!fsnotify_iter_should_report_type(iter_info, type))
	continue;
	mark = iter_info->marks[type];
	if (mark &&
	!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
	mark->ignored_mask = 0;
	}
	}

	fsnotify_foreach_obj_type(type) {
	if (!fsnotify_iter_should_report_type(iter_info, type))
	continue;
	mark = iter_info->marks[type];
	/* does the object mark tell us to do something? */
	if (mark) {
	group = mark->group;
	marks_mask \|= mark->mask;
	marks_ignored_mask \|= mark->ignored_mask;
	}
	}

	pr_debug("%s: group=%p to_tell=%p mask=%x marks_mask=%x marks_ignored_mask=%x"
	" data=%p data_is=%d cookie=%d\n",
	__func__, group, to_tell, mask, marks_mask, marks_ignored_mask,
	data, data_is, cookie);

	if (!(test_mask & marks_mask & ~marks_ignored_mask))
	return 0;

	return group->ops->handle_event(group, to_tell, mask, data, data_is,
	file_name, cookie, iter_info);
	}

	static struct fsnotify_mark fsnotify_first_mark(struct fsnotify_mark_connector *connp)
	{
	struct fsnotify_mark_connector *conn;
	struct hlist_node *node = NULL;

	conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
	if (conn)
	node = srcu_dereference(conn->list.first, &fsnotify_mark_srcu);

	return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
	}

	static struct fsnotify_mark fsnotify_next_mark(struct fsnotify_mark mark)
	{
	struct hlist_node *node = NULL;

	if (mark)
	node = srcu_dereference(mark->obj_list.next,
	&fsnotify_mark_srcu);

	return hlist_entry_safe(node, struct fsnotify_mark, obj_list);
	}

	/*
	* iter_info is a multi head priority queue of marks.
	* Pick a subset of marks from queue heads, all with the
	* same group and set the report_mask for selected subset.
	* Returns the report_mask of the selected subset.
	*/
	static unsigned int fsnotify_iter_select_report_types(
	struct fsnotify_iter_info *iter_info)
	{
	struct fsnotify_group *max_prio_group = NULL;
	struct fsnotify_mark *mark;
	int type;

	/* Choose max prio group among groups of all queue heads */
	fsnotify_foreach_obj_type(type) {
	mark = iter_info->marks[type];
	if (mark &&
	fsnotify_compare_groups(max_prio_group, mark->group) > 0)
	max_prio_group = mark->group;
	}

	if (!max_prio_group)
	return 0;

	/* Set the report mask for marks from same group as max prio group */
	iter_info->report_mask = 0;
	fsnotify_foreach_obj_type(type) {
	mark = iter_info->marks[type];
	if (mark &&
	fsnotify_compare_groups(max_prio_group, mark->group) == 0)
	fsnotify_iter_set_report_type(iter_info, type);
	}

	return iter_info->report_mask;
	}

	/*
	* Pop from iter_info multi head queue, the marks that were iterated in the
	* current iteration step.
	*/
	static void fsnotify_iter_next(struct fsnotify_iter_info *iter_info)
	{
	int type;

	fsnotify_foreach_obj_type(type) {
	if (fsnotify_iter_should_report_type(iter_info, type))
	iter_info->marks[type] =
	fsnotify_next_mark(iter_info->marks[type]);
	}
	}

	/*
	* 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, const void data, int data_is,
	const struct qstr *file_name, u32 cookie)
	{
	struct fsnotify_iter_info iter_info = {};
	struct super_block *sb = to_tell->i_sb;
	struct mount *mnt = NULL;
	__u32 mnt_or_sb_mask = sb->s_fsnotify_mask;
	int ret = 0;
	__u32 test_mask = (mask & ALL_FSNOTIFY_EVENTS);

	if (data_is == FSNOTIFY_EVENT_PATH) {
	mnt = real_mount(((const struct path *)data)->mnt);
	mnt_or_sb_mask \|= mnt->mnt_fsnotify_mask;
	}
	/* An event "on child" is not intended for a mount/sb mark */
	if (mask & FS_EVENT_ON_CHILD)
	mnt_or_sb_mask = 0;

	/*
	* Optimization: srcu_read_lock() has a memory barrier which can
	* be expensive. It protects walking the *_fsnotify_marks lists.
	* However, if we do not walk the lists, we do not have to do
	* SRCU because we have no references to any objects and do not
	* need SRCU to keep them "alive".
	*/
	if (!to_tell->i_fsnotify_marks && !sb->s_fsnotify_marks &&
	(!mnt \|\| !mnt->mnt_fsnotify_marks))
	return 0;
	/*
	* if this is a modify event we may need to clear the ignored masks
	* otherwise return if neither the inode nor the vfsmount/sb care about
	* this type of event.
	*/
	if (!(mask & FS_MODIFY) &&
	!(test_mask & (to_tell->i_fsnotify_mask \| mnt_or_sb_mask)))
	return 0;

	iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);

	iter_info.marks[FSNOTIFY_OBJ_TYPE_INODE] =
	fsnotify_first_mark(&to_tell->i_fsnotify_marks);
	iter_info.marks[FSNOTIFY_OBJ_TYPE_SB] =
	fsnotify_first_mark(&sb->s_fsnotify_marks);
	if (mnt) {
	iter_info.marks[FSNOTIFY_OBJ_TYPE_VFSMOUNT] =
	fsnotify_first_mark(&mnt->mnt_fsnotify_marks);
	}

	/*
	* We need to merge inode/vfsmount/sb mark lists so that e.g. inode mark
	* ignore masks are properly reflected for mount/sb mark notifications.
	* That's why this traversal is so complicated...
	*/
	while (fsnotify_iter_select_report_types(&iter_info)) {
	ret = send_to_group(to_tell, mask, data, data_is, cookie,
	file_name, &iter_info);

	if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
	goto out;

	fsnotify_iter_next(&iter_info);
	}
	ret = 0;
	out:
	srcu_read_unlock(&fsnotify_mark_srcu, iter_info.srcu_idx);

	return ret;
	}
	EXPORT_SYMBOL_GPL(fsnotify);

	extern struct kmem_cache *fsnotify_mark_connector_cachep;

	static __init int fsnotify_init(void)
	{
	int ret;

	BUILD_BUG_ON(HWEIGHT32(ALL_FSNOTIFY_BITS) != 25);

	ret = init_srcu_struct(&fsnotify_mark_srcu);
	if (ret)
	panic("initializing fsnotify_mark_srcu");

	fsnotify_mark_connector_cachep = KMEM_CACHE(fsnotify_mark_connector,
	SLAB_PANIC);

	return 0;
	}
	core_initcall(fsnotify_init);