/*
 * fs/inotify_user.c - inotify support for userspace
 *
 * Authors:
 *      John McCutchan  <ttb@tentacle.dhs.org>
 *      Robert Love     <rml@novell.com>
 *
 * Copyright (C) 2005 John McCutchan
 * Copyright 2006 Hewlett-Packard Development Company, L.P.
 *
 * Copyright (C) 2009 Eric Paris <Red Hat Inc>
 * inotify was largely rewriten to make use of the fsnotify infrastructure
 *
 * 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.
 */

#include <linux/dcache.h> /* d_unlinked */
#include <linux/fs.h> /* struct inode */
#include <linux/fsnotify_backend.h>
#include <linux/inotify.h>
#include <linux/path.h> /* struct path */
#include <linux/slab.h> /* kmem_* */
#include <linux/types.h>
#include <linux/sched.h>

#include "inotify.h"

/*
 * Check if 2 events contain the same information.  We do not compare private data
 * but at this moment that isn't a problem for any know fsnotify listeners.
 */
static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new)
{
        if ((old->mask == new->mask) &&
            (old->to_tell == new->to_tell) &&
            (old->data_type == new->data_type) &&
            (old->name_len == new->name_len)) {
                switch (old->data_type) {
                case (FSNOTIFY_EVENT_INODE):
                        /* remember, after old was put on the wait_q we aren't
                         * allowed to look at the inode any more, only thing
                         * left to check was if the file_name is the same */
                        if (!old->name_len ||
                            !strcmp(old->file_name, new->file_name))
                                return true;
                        break;
                case (FSNOTIFY_EVENT_PATH):
                        if ((old->path.mnt == new->path.mnt) &&
                            (old->path.dentry == new->path.dentry))
                                return true;
                        break;
                case (FSNOTIFY_EVENT_NONE):
                        if (old->mask & FS_Q_OVERFLOW)
                                return true;
                        else if (old->mask & FS_IN_IGNORED)
                                return false;
                        return true;
                };
        }
        return false;
}

static struct fsnotify_event *inotify_merge(struct list_head *list,
                                            struct fsnotify_event *event)
{
        struct fsnotify_event_holder *last_holder;
        struct fsnotify_event *last_event;

        /* and the list better be locked by something too */
        spin_lock(&event->lock);

        last_holder = list_entry(list->prev, struct fsnotify_event_holder, event_list);
        last_event = last_holder->event;
        if (event_compare(last_event, event))
                fsnotify_get_event(last_event);
        else
                last_event = NULL;

        spin_unlock(&event->lock);

        return last_event;
}

static int inotify_handle_event(struct fsnotify_group *group,
                                struct fsnotify_mark *inode_mark,
                                struct fsnotify_mark *vfsmount_mark,
                                struct fsnotify_event *event)
{
        struct inotify_inode_mark *i_mark;
        struct inode *to_tell;
        struct inotify_event_private_data *event_priv;
        struct fsnotify_event_private_data *fsn_event_priv;
        struct fsnotify_event *added_event;
        int wd, ret = 0;

        BUG_ON(vfsmount_mark);

        pr_debug("%s: group=%p event=%p to_tell=%p mask=%x\n", __func__, group,
                 event, event->to_tell, event->mask);

        to_tell = event->to_tell;

        i_mark = container_of(inode_mark, struct inotify_inode_mark,
                              fsn_mark);
        wd = i_mark->wd;

        event_priv = kmem_cache_alloc(event_priv_cachep, GFP_KERNEL);
        if (unlikely(!event_priv))
                return -ENOMEM;

        fsn_event_priv = &event_priv->fsnotify_event_priv_data;

        fsn_event_priv->group = group;
        event_priv->wd = wd;

        added_event = fsnotify_add_notify_event(group, event, fsn_event_priv, inotify_merge);
        if (added_event) {
                inotify_free_event_priv(fsn_event_priv);
                if (!IS_ERR(added_event))
                        fsnotify_put_event(added_event);
                else
                        ret = PTR_ERR(added_event);
        }

        if (inode_mark->mask & IN_ONESHOT)
                fsnotify_destroy_mark(inode_mark);

        return ret;
}

static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
{
        inotify_ignored_and_remove_idr(fsn_mark, group);
}

static bool inotify_should_send_event(struct fsnotify_group *group, struct inode *inode,
                                      struct fsnotify_mark *inode_mark,
                                      struct fsnotify_mark *vfsmount_mark,
                                      __u32 mask, void *data, int data_type)
{
        if ((inode_mark->mask & FS_EXCL_UNLINK) &&
            (data_type == FSNOTIFY_EVENT_PATH)) {
                struct path *path = data;

                if (d_unlinked(path->dentry))
                        return false;
        }

        return true;
}

/*
 * This is NEVER supposed to be called.  Inotify marks should either have been
 * removed from the idr when the watch was removed or in the
 * fsnotify_destroy_mark_by_group() call when the inotify instance was being
 * torn down.  This is only called if the idr is about to be freed but there
 * are still marks in it.
 */
static int idr_callback(int id, void *p, void *data)
{
        struct fsnotify_mark *fsn_mark;
        struct inotify_inode_mark *i_mark;
        static bool warned = false;

        if (warned)
                return 0;

        warned = true;
        fsn_mark = p;
        i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);

        WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
                "idr.  Probably leaking memory\n", id, p, data);

        /*
         * I'm taking the liberty of assuming that the mark in question is a
         * valid address and I'm dereferencing it.  This might help to figure
         * out why we got here and the panic is no worse than the original
         * BUG() that was here.
         */
        if (fsn_mark)
                printk(KERN_WARNING "fsn_mark->group=%p inode=%p wd=%d\n",
                        fsn_mark->group, fsn_mark->i.inode, i_mark->wd);
        return 0;
}

static void inotify_free_group_priv(struct fsnotify_group *group)
{
        /* ideally the idr is empty and we won't hit the BUG in the callback */
        idr_for_each(&group->inotify_data.idr, idr_callback, group);
        idr_remove_all(&group->inotify_data.idr);
        idr_destroy(&group->inotify_data.idr);
        atomic_dec(&group->inotify_data.user->inotify_devs);
        free_uid(group->inotify_data.user);
}

void inotify_free_event_priv(struct fsnotify_event_private_data *fsn_event_priv)
{
        struct inotify_event_private_data *event_priv;


        event_priv = container_of(fsn_event_priv, struct inotify_event_private_data,
                                  fsnotify_event_priv_data);

        kmem_cache_free(event_priv_cachep, event_priv);
}

const struct fsnotify_ops inotify_fsnotify_ops = {
        .handle_event = inotify_handle_event,
        .should_send_event = inotify_should_send_event,
        .free_group_priv = inotify_free_group_priv,
        .free_event_priv = inotify_free_event_priv,
        .freeing_mark = inotify_freeing_mark,
};