inotify_fsnotify.c

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/*
 * fs/inotify_user.c - inotify support for userspace
 *
 * Authors:
 *  John McCutchan  <[email protected]>
 *  Robert Love <[email protected]>
 *
 * 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,
};