// 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(inode, FS_UNMOUNT);

  
  		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);

  }

  /* Are inode/sb/mount interested in parent and name info with this event? */
  static bool fsnotify_event_needs_parent(struct inode *inode, struct mount *mnt,
  					__u32 mask)
  {
  	__u32 marks_mask = 0;
  
  	/* We only send parent/name to inode/sb/mount for events on non-dir */
  	if (mask & FS_ISDIR)
  		return false;

  	/*
  	 * All events that are possible on child can also may be reported with
  	 * parent/name info to inode/sb/mount.  Otherwise, a watching parent
  	 * could result in events reported with unexpected name info to sb/mount.
  	 */
  	BUILD_BUG_ON(FS_EVENTS_POSS_ON_CHILD & ~FS_EVENTS_POSS_TO_PARENT);

  	/* Did either inode/sb/mount subscribe for events with parent/name? */
  	marks_mask |= fsnotify_parent_needed_mask(inode->i_fsnotify_mask);
  	marks_mask |= fsnotify_parent_needed_mask(inode->i_sb->s_fsnotify_mask);
  	if (mnt)
  		marks_mask |= fsnotify_parent_needed_mask(mnt->mnt_fsnotify_mask);
  
  	/* Did they subscribe for this event with parent/name info? */
  	return mask & marks_mask;
  }

  /*
   * Notify this dentry's parent about a child's events with child name info

   * if parent is watching or if inode/sb/mount are interested in events with
   * parent and name info.
   *
   * Notify only the child without name info if parent is not watching and
   * inode/sb/mount are not interested in events with parent and name info.

   */

  int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,

  		      int data_type)

  {

  	const struct path *path = fsnotify_data_path(data, data_type);
  	struct mount *mnt = path ? real_mount(path->mnt) : NULL;

  	struct inode *inode = d_inode(dentry);

  	struct dentry *parent;

  	bool parent_watched = dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED;

  	bool parent_needed, parent_interested;

  	__u32 p_mask;

  	struct inode *p_inode = NULL;

  	struct name_snapshot name;
  	struct qstr *file_name = NULL;

  	int ret = 0;

  	/*
  	 * Do inode/sb/mount care about parent and name info on non-dir?
  	 * Do they care about any event at all?
  	 */
  	if (!inode->i_fsnotify_marks && !inode->i_sb->s_fsnotify_marks &&
  	    (!mnt || !mnt->mnt_fsnotify_marks) && !parent_watched)
  		return 0;

  	parent = NULL;

  	parent_needed = fsnotify_event_needs_parent(inode, mnt, mask);
  	if (!parent_watched && !parent_needed)

  		goto notify;

  	/* Does parent inode care about events on children? */

  	parent = dget_parent(dentry);

  	p_inode = parent->d_inode;

  	p_mask = fsnotify_inode_watches_children(p_inode);
  	if (unlikely(parent_watched && !p_mask))

  		__fsnotify_update_child_dentry_flags(p_inode);

  
  	/*
  	 * Include parent/name in notification either if some notification

  	 * groups require parent info or the parent is interested in this event.

  	 */

  	parent_interested = mask & p_mask & ALL_FSNOTIFY_EVENTS;
  	if (parent_needed || parent_interested) {

  		/* When notifying parent, child should be passed as data */
  		WARN_ON_ONCE(inode != fsnotify_data_inode(data, data_type));

  		/* Notify both parent and child with child name info */

  		take_dentry_name_snapshot(&name, dentry);

  		file_name = &name.name;

  		if (parent_interested)

  			mask |= FS_EVENT_ON_CHILD;

  	}

  notify:

  	ret = fsnotify(mask, data, data_type, p_inode, file_name, inode, 0);

  	if (file_name)
  		release_dentry_name_snapshot(&name);
  	dput(parent);

  	return ret;

  }

  EXPORT_SYMBOL_GPL(__fsnotify_parent);

  static int fsnotify_handle_inode_event(struct fsnotify_group *group,
  				       struct fsnotify_mark *inode_mark,
  				       u32 mask, const void *data, int data_type,
  				       struct inode *dir, const struct qstr *name,
  				       u32 cookie)
  {
  	const struct path *path = fsnotify_data_path(data, data_type);
  	struct inode *inode = fsnotify_data_inode(data, data_type);
  	const struct fsnotify_ops *ops = group->ops;
  
  	if (WARN_ON_ONCE(!ops->handle_inode_event))
  		return 0;
  
  	if ((inode_mark->mask & FS_EXCL_UNLINK) &&
  	    path && d_unlinked(path->dentry))
  		return 0;

  	/* Check interest of this mark in case event was sent with two marks */
  	if (!(mask & inode_mark->mask & ALL_FSNOTIFY_EVENTS))
  		return 0;

  	return ops->handle_inode_event(inode_mark, mask, inode, dir, name, cookie);
  }

  static int fsnotify_handle_event(struct fsnotify_group *group, __u32 mask,
  				 const void *data, int data_type,
  				 struct inode *dir, const struct qstr *name,
  				 u32 cookie, struct fsnotify_iter_info *iter_info)
  {
  	struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);

  	struct fsnotify_mark *parent_mark = fsnotify_iter_parent_mark(iter_info);

  	int ret;

  	if (WARN_ON_ONCE(fsnotify_iter_sb_mark(iter_info)) ||
  	    WARN_ON_ONCE(fsnotify_iter_vfsmount_mark(iter_info)))
  		return 0;

  	if (parent_mark) {
  		/*
  		 * parent_mark indicates that the parent inode is watching
  		 * children and interested in this event, which is an event
  		 * possible on child. But is *this mark* watching children and
  		 * interested in this event?
  		 */
  		if (parent_mark->mask & FS_EVENT_ON_CHILD) {
  			ret = fsnotify_handle_inode_event(group, parent_mark, mask,
  							  data, data_type, dir, name, 0);
  			if (ret)
  				return ret;
  		}
  		if (!inode_mark)
  			return 0;
  	}
  
  	if (mask & FS_EVENT_ON_CHILD) {
  		/*
  		 * Some events can be sent on both parent dir and child marks
  		 * (e.g. FS_ATTRIB).  If both parent dir and child are
  		 * watching, report the event once to parent dir with name (if
  		 * interested) and once to child without name (if interested).
  		 * The child watcher is expecting an event without a file name
  		 * and without the FS_EVENT_ON_CHILD flag.
  		 */
  		mask &= ~FS_EVENT_ON_CHILD;

  		dir = NULL;
  		name = NULL;
  	}

  	return fsnotify_handle_inode_event(group, inode_mark, mask, data, data_type,
  					   dir, name, cookie);

  }

  static int send_to_group(__u32 mask, const void *data, int data_type,
  			 struct inode *dir, const struct qstr *file_name,
  			 u32 cookie, 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 mask=%x marks_mask=%x marks_ignored_mask=%x data=%p data_type=%d dir=%p cookie=%d
  ",
  		 __func__, group, mask, marks_mask, marks_ignored_mask,
  		 data, data_type, dir, cookie);

  	if (!(test_mask & marks_mask & ~marks_ignored_mask))

  		return 0;

  	if (group->ops->handle_event) {
  		return group->ops->handle_event(group, mask, data, data_type, dir,
  						file_name, cookie, iter_info);
  	}
  
  	return fsnotify_handle_event(group, mask, data, data_type, dir,
  				     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]);
  	}

  }
  
  /*

   * fsnotify - 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.
   *
   * @mask:	event type and flags
   * @data:	object that event happened on
   * @data_type:	type of object for fanotify_data_XXX() accessors
   * @dir:	optional directory associated with event -
   *		if @file_name is not NULL, this is the directory that
   *		@file_name is relative to
   * @file_name:	optional file name associated with event
   * @inode:	optional inode associated with event -
   *		either @dir or @inode must be non-NULL.
   *		if both are non-NULL event may be reported to both.
   * @cookie:	inotify rename cookie

   */

  int fsnotify(__u32 mask, const void *data, int data_type, struct inode *dir,
  	     const struct qstr *file_name, struct inode *inode, u32 cookie)

  {

  	const struct path *path = fsnotify_data_path(data, data_type);

  	struct fsnotify_iter_info iter_info = {};

  	struct super_block *sb;

  	struct mount *mnt = NULL;

  	struct inode *parent = NULL;

  	int ret = 0;

  	__u32 test_mask, marks_mask;

  	if (path)

  		mnt = real_mount(path->mnt);

  	if (!inode) {
  		/* Dirent event - report on TYPE_INODE to dir */
  		inode = dir;
  	} else if (mask & FS_EVENT_ON_CHILD) {
  		/*

  		 * Event on child - report on TYPE_PARENT to dir if it is
  		 * watching children and on TYPE_INODE to child.

  		 */

  		parent = dir;

  	}
  	sb = inode->i_sb;

  	/*

  	 * 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 (!sb->s_fsnotify_marks &&

  	    (!mnt || !mnt->mnt_fsnotify_marks) &&

  	    (!inode || !inode->i_fsnotify_marks) &&

  	    (!parent || !parent->i_fsnotify_marks))

  		return 0;

  	marks_mask = sb->s_fsnotify_mask;

  	if (mnt)
  		marks_mask |= mnt->mnt_fsnotify_mask;

  	if (inode)
  		marks_mask |= inode->i_fsnotify_mask;

  	if (parent)
  		marks_mask |= parent->i_fsnotify_mask;

  	/*

  	 * if this is a modify event we may need to clear the ignored masks

  	 * otherwise return if none of the marks care about this type of event.

  	 */

  	test_mask = (mask & ALL_FSNOTIFY_EVENTS);
  	if (!(mask & FS_MODIFY) && !(test_mask & marks_mask))

  		return 0;

  	iter_info.srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);

  	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);

  	}

  	if (inode) {
  		iter_info.marks[FSNOTIFY_OBJ_TYPE_INODE] =
  			fsnotify_first_mark(&inode->i_fsnotify_marks);
  	}

  	if (parent) {
  		iter_info.marks[FSNOTIFY_OBJ_TYPE_PARENT] =
  			fsnotify_first_mark(&parent->i_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(mask, data, data_type, dir, file_name,
  				    cookie, &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);
  
  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);