/*
 *  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/spinlock.h>

#include <linux/atomic.h>

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

#include "../internal.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_rcu(&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_rcu(&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 clear all of the inode marks associated with that group.
 */
void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
{
        fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
}

/*
 * 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;
}

/*
 * If we are setting a mark mask on an inode mark we should pin the inode
 * in memory.
 */
void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
                                         __u32 mask)
{
        struct inode *inode;

        assert_spin_locked(&mark->lock);

        if (mask &&
            mark->i.inode &&
            !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
                mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
                inode = igrab(mark->i.inode);
                /*
                 * we shouldn't be able to get here if the inode wasn't
                 * already safely held in memory.  But bug in case it
                 * ever is wrong.
                 */
                BUG_ON(!inode);
        }
}

/*
 * Attach an initialized mark to a given 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.  These
 * marks are ordered according to priority, highest number first, and then by
 * the group's location in memory.
 */
int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
                            struct fsnotify_group *group, struct inode *inode,
                            int allow_dups)
{
        struct fsnotify_mark *lmark;
        struct hlist_node *node, *last = NULL;
        int ret = 0;

        mark->flags |= FSNOTIFY_MARK_FLAG_INODE;

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

        spin_lock(&inode->i_lock);

        mark->i.inode = inode;

        /* is mark the first mark? */
        if (hlist_empty(&inode->i_fsnotify_marks)) {
                hlist_add_head_rcu(&mark->i.i_list, &inode->i_fsnotify_marks);
                goto out;
        }

        /* should mark be in the middle of the current list? */
        hlist_for_each_entry(lmark, node, &inode->i_fsnotify_marks, i.i_list) {
                last = node;

                if ((lmark->group == group) && !allow_dups) {
                        ret = -EEXIST;
                        goto out;
                }

                if (mark->group->priority < lmark->group->priority)
                        continue;

                if ((mark->group->priority == lmark->group->priority) &&
                    (mark->group < lmark->group))
                        continue;

                hlist_add_before_rcu(&mark->i.i_list, &lmark->i.i_list);
                goto out;
        }

        BUG_ON(last == NULL);
        /* mark should be the last entry.  last is the current last entry */
        hlist_add_after_rcu(last, &mark->i.i_list);
out:
        fsnotify_recalc_inode_mask_locked(inode);
        spin_unlock(&inode->i_lock);

        return ret;
}

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

        spin_lock(&inode_sb_list_lock);
        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_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 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)) {
                        spin_unlock(&inode->i_lock);
                        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;
                spin_unlock(&inode->i_lock);

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

                /*
                 * We can safely drop inode_sb_list_lock here because we hold
                 * references on both inode and next_i.  Also no new inodes
                 * will be added since the umount has begun.
                 */
                spin_unlock(&inode_sb_list_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_sb_list_lock);
        }
        spin_unlock(&inode_sb_list_lock);
}