/*
 *  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/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/writeback.h> /* for inode_lock */

#include <asm/atomic.h>

#include <linux/fsnotify_backend.h>
#include "fsnotify.h"

/*
 * Recalculate the mask of events relevant to a given inode locked.
 */
static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
{
	struct fsnotify_mark *mark;
	struct hlist_node *pos;
	__u32 new_mask = 0;

	assert_spin_locked(&inode->i_lock);

	hlist_for_each_entry(mark, pos, &inode->i_fsnotify_marks, i.i_list)
		new_mask |= mark->mask;
	inode->i_fsnotify_mask = new_mask;
}

/*
 * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
 * any notifier is interested in hearing for this inode.
 */
void fsnotify_recalc_inode_mask(struct inode *inode)
{
	spin_lock(&inode->i_lock);
	fsnotify_recalc_inode_mask_locked(inode);
	spin_unlock(&inode->i_lock);

	__fsnotify_update_child_dentry_flags(inode);
}

void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
{
	struct inode *inode = mark->i.inode;

	assert_spin_locked(&mark->lock);
	assert_spin_locked(&mark->group->mark_lock);

	spin_lock(&inode->i_lock);

	hlist_del_init(&mark->i.i_list);
	mark->i.inode = NULL;

	/*
	 * this mark is now off the inode->i_fsnotify_marks list and we
	 * hold the inode->i_lock, so this is the perfect time to update the
	 * inode->i_fsnotify_mask
	 */
	fsnotify_recalc_inode_mask_locked(inode);

	spin_unlock(&inode->i_lock);
}

/*
 * Given an inode, destroy all of the marks associated with that inode.
 */
void fsnotify_clear_marks_by_inode(struct inode *inode)
{
	struct fsnotify_mark *mark, *lmark;
	struct hlist_node *pos, *n;
	LIST_HEAD(free_list);

	spin_lock(&inode->i_lock);
	hlist_for_each_entry_safe(mark, pos, n, &inode->i_fsnotify_marks, i.i_list) {
		list_add(&mark->i.free_i_list, &free_list);
		hlist_del_init(&mark->i.i_list);
		fsnotify_get_mark(mark);
	}
	spin_unlock(&inode->i_lock);

	list_for_each_entry_safe(mark, lmark, &free_list, i.free_i_list) {
		fsnotify_destroy_mark(mark);
		fsnotify_put_mark(mark);
	}
}

/*
 * given a group and inode, find the mark associated with that combination.
 * if found take a reference to that mark and return it, else return NULL
 */
struct fsnotify_mark *fsnotify_find_inode_mark_locked(struct fsnotify_group *group,
						      struct inode *inode)
{
	struct fsnotify_mark *mark;
	struct hlist_node *pos;

	assert_spin_locked(&inode->i_lock);

	hlist_for_each_entry(mark, pos, &inode->i_fsnotify_marks, i.i_list) {
		if (mark->group == group) {
			fsnotify_get_mark(mark);
			return mark;
		}
	}
	return NULL;
}

/*
 * given a group and inode, find the mark associated with that combination.
 * if found take a reference to that mark and return it, else return NULL
 */
struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
					       struct inode *inode)
{
	struct fsnotify_mark *mark;

	spin_lock(&inode->i_lock);
	mark = fsnotify_find_inode_mark_locked(group, inode);
	spin_unlock(&inode->i_lock);

	return mark;
}

/*
 * Attach an initialized mark mark to a given group and inode.
 * These marks may be used for the fsnotify backend to determine which
 * event types should be delivered to which group and for which inodes.
 */
int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
			    struct fsnotify_group *group, struct inode *inode,
			    int allow_dups)
{
	struct fsnotify_mark *lmark = NULL;
	int ret = 0;

	inode = igrab(inode);
	if (unlikely(!inode))
		return -EINVAL;

	mark->flags = FSNOTIFY_MARK_FLAG_INODE;

	assert_spin_locked(&mark->lock);
	assert_spin_locked(&group->mark_lock);

	spin_lock(&inode->i_lock);

	if (!allow_dups)
		lmark = fsnotify_find_inode_mark_locked(group, inode);
	if (!lmark) {
		mark->i.inode = inode;

		hlist_add_head(&mark->i.i_list, &inode->i_fsnotify_marks);

		fsnotify_recalc_inode_mask_locked(inode);
	}

	spin_unlock(&inode->i_lock);

	if (lmark) {
		ret = -EEXIST;
		iput(inode);
	}

	return ret;
}

/**
 * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
 * @list: list of inodes being unmounted (sb->s_inodes)
 *
 * Called with inode_lock held, protecting the unmounting super block's list
 * of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
 * We temporarily drop inode_lock, however, and CAN block.
 */
void fsnotify_unmount_inodes(struct list_head *list)
{
	struct inode *inode, *next_i, *need_iput = NULL;

	list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
		struct inode *need_iput_tmp;

		/*
		 * We cannot __iget() an inode in state I_CLEAR, I_FREEING,
		 * I_WILL_FREE, or I_NEW which is fine because by that point
		 * the inode cannot have any associated watches.
		 */
		if (inode->i_state & (I_CLEAR|I_FREEING|I_WILL_FREE|I_NEW))
			continue;

		/*
		 * If i_count is zero, the inode cannot have any watches and
		 * doing an __iget/iput with MS_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.
		 */
		if (!atomic_read(&inode->i_count))
			continue;

		need_iput_tmp = need_iput;
		need_iput = NULL;

		/* In case fsnotify_inode_delete() drops a reference. */
		if (inode != need_iput_tmp)
			__iget(inode);
		else
			need_iput_tmp = NULL;

		/* In case the dropping of a reference would nuke next_i. */
		if ((&next_i->i_sb_list != list) &&
		    atomic_read(&next_i->i_count) &&
		    !(next_i->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))) {
			__iget(next_i);
			need_iput = next_i;
		}

		/*
		 * We can safely drop inode_lock here because we hold
		 * references on both inode and next_i.  Also no new inodes
		 * will be added since the umount has begun.  Finally,
		 * iprune_mutex keeps shrink_icache_memory() away.
		 */
		spin_unlock(&inode_lock);

		if (need_iput_tmp)
			iput(need_iput_tmp);

		/* 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);

		spin_lock(&inode_lock);
	}
}