fs/notify/inotify/inotify_fsnotify.c

   1 /*
   2  * fs/inotify_user.c - inotify support for userspace
   3  *
   4  * Authors:
   5  *      John McCutchan  <ttb@tentacle.dhs.org>
   6  *      Robert Love     <rml@novell.com>
   7  *
   8  * Copyright (C) 2005 John McCutchan
   9  * Copyright 2006 Hewlett-Packard Development Company, L.P.
  10  *
  11  * Copyright (C) 2009 Eric Paris <Red Hat Inc>
  12  * inotify was largely rewriten to make use of the fsnotify infrastructure
  13  *
  14  * This program is free software; you can redistribute it and/or modify it
  15  * under the terms of the GNU General Public License as published by the
  16  * Free Software Foundation; either version 2, or (at your option) any
  17  * later version.
  18  *
  19  * This program is distributed in the hope that it will be useful, but
  20  * WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  22  * General Public License for more details.
  23  */
  24
  25 #include <linux/dcache.h> /* d_unlinked */
  26 #include <linux/fs.h> /* struct inode */
  27 #include <linux/fsnotify_backend.h>
  28 #include <linux/inotify.h>
  29 #include <linux/path.h> /* struct path */
  30 #include <linux/slab.h> /* kmem_* */
  31 #include <linux/types.h>
  32 #include <linux/sched.h>
  33
  34 #include "inotify.h"
  35
  36 /*
  37  * Check if 2 events contain the same information.  We do not compare private data
  38  * but at this moment that isn't a problem for any know fsnotify listeners.
  39  */
  40 static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new)
  41 {
  42         if ((old->mask == new->mask) &&
  43             (old->to_tell == new->to_tell) &&
  44             (old->data_type == new->data_type) &&
  45             (old->name_len == new->name_len)) {
  46                 switch (old->data_type) {
  47                 case (FSNOTIFY_EVENT_INODE):
  48                         /* remember, after old was put on the wait_q we aren't
  49                          * allowed to look at the inode any more, only thing
  50                          * left to check was if the file_name is the same */
  51                         if (!old->name_len ||
  52                             !strcmp(old->file_name, new->file_name))
  53                                 return true;
  54                         break;
  55                 case (FSNOTIFY_EVENT_PATH):
  56                         if ((old->path.mnt == new->path.mnt) &&
  57                             (old->path.dentry == new->path.dentry))
  58                                 return true;
  59                         break;
  60                 case (FSNOTIFY_EVENT_NONE):
  61                         if (old->mask & FS_Q_OVERFLOW)
  62                                 return true;
  63                         else if (old->mask & FS_IN_IGNORED)
  64                                 return false;
  65                         return true;
  66                 };
  67         }
  68         return false;
  69 }
  70
  71 static struct fsnotify_event *inotify_merge(struct list_head *list,
  72                                             struct fsnotify_event *event)
  73 {
  74         struct fsnotify_event_holder *last_holder;
  75         struct fsnotify_event *last_event;
  76
  77         /* and the list better be locked by something too */
  78         spin_lock(&event->lock);
  79
  80         last_holder = list_entry(list->prev, struct fsnotify_event_holder, event_list);
  81         last_event = last_holder->event;
  82         if (event_compare(last_event, event))
  83                 fsnotify_get_event(last_event);
  84         else
  85                 last_event = NULL;
  86
  87         spin_unlock(&event->lock);
  88
  89         return last_event;
  90 }
  91
  92 static int inotify_handle_event(struct fsnotify_group *group,
  93                                 struct fsnotify_mark *inode_mark,
  94                                 struct fsnotify_mark *vfsmount_mark,
  95                                 struct fsnotify_event *event)
  96 {
  97         struct inotify_inode_mark *i_mark;
  98         struct inode *to_tell;
  99         struct inotify_event_private_data *event_priv;
 100         struct fsnotify_event_private_data *fsn_event_priv;
 101         struct fsnotify_event *added_event;
 102         int wd, ret = 0;
 103
 104         BUG_ON(vfsmount_mark);
 105
 106         pr_debug("%s: group=%p event=%p to_tell=%p mask=%x\n", __func__, group,
 107                  event, event->to_tell, event->mask);
 108
 109         to_tell = event->to_tell;
 110
 111         i_mark = container_of(inode_mark, struct inotify_inode_mark,
 112                               fsn_mark);
 113         wd = i_mark->wd;
 114
 115         event_priv = kmem_cache_alloc(event_priv_cachep, GFP_KERNEL);
 116         if (unlikely(!event_priv))
 117                 return -ENOMEM;
 118
 119         fsn_event_priv = &event_priv->fsnotify_event_priv_data;
 120
 121         fsn_event_priv->group = group;
 122         event_priv->wd = wd;
 123
 124         added_event = fsnotify_add_notify_event(group, event, fsn_event_priv, inotify_merge);
 125         if (added_event) {
 126                 inotify_free_event_priv(fsn_event_priv);
 127                 if (!IS_ERR(added_event))
 128                         fsnotify_put_event(added_event);
 129                 else
 130                         ret = PTR_ERR(added_event);
 131         }
 132
 133         if (inode_mark->mask & IN_ONESHOT)
 134                 fsnotify_destroy_mark(inode_mark);
 135
 136         return ret;
 137 }
 138
 139 static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
 140 {
 141         inotify_ignored_and_remove_idr(fsn_mark, group);
 142 }
 143
 144 static bool inotify_should_send_event(struct fsnotify_group *group, struct inode *inode,
 145                                       struct fsnotify_mark *inode_mark,
 146                                       struct fsnotify_mark *vfsmount_mark,
 147                                       __u32 mask, void *data, int data_type)
 148 {
 149         if ((inode_mark->mask & FS_EXCL_UNLINK) &&
 150             (data_type == FSNOTIFY_EVENT_PATH)) {
 151                 struct path *path = data;
 152
 153                 if (d_unlinked(path->dentry))
 154                         return false;
 155         }
 156
 157         return true;
 158 }
 159
 160 /*
 161  * This is NEVER supposed to be called.  Inotify marks should either have been
 162  * removed from the idr when the watch was removed or in the
 163  * fsnotify_destroy_mark_by_group() call when the inotify instance was being
 164  * torn down.  This is only called if the idr is about to be freed but there
 165  * are still marks in it.
 166  */
 167 static int idr_callback(int id, void *p, void *data)
 168 {
 169         struct fsnotify_mark *fsn_mark;
 170         struct inotify_inode_mark *i_mark;
 171         static bool warned = false;
 172
 173         if (warned)
 174                 return 0;
 175
 176         warned = true;
 177         fsn_mark = p;
 178         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
 179
 180         WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
 181                 "idr.  Probably leaking memory\n", id, p, data);
 182
 183         /*
 184          * I'm taking the liberty of assuming that the mark in question is a
 185          * valid address and I'm dereferencing it.  This might help to figure
 186          * out why we got here and the panic is no worse than the original
 187          * BUG() that was here.
 188          */
 189         if (fsn_mark)
 190                 printk(KERN_WARNING "fsn_mark->group=%p inode=%p wd=%d\n",
 191                         fsn_mark->group, fsn_mark->i.inode, i_mark->wd);
 192         return 0;
 193 }
 194
 195 static void inotify_free_group_priv(struct fsnotify_group *group)
 196 {
 197         /* ideally the idr is empty and we won't hit the BUG in the callback */
 198         idr_for_each(&group->inotify_data.idr, idr_callback, group);
 199         idr_remove_all(&group->inotify_data.idr);
 200         idr_destroy(&group->inotify_data.idr);
 201         atomic_dec(&group->inotify_data.user->inotify_devs);
 202         free_uid(group->inotify_data.user);
 203 }
 204
 205 void inotify_free_event_priv(struct fsnotify_event_private_data *fsn_event_priv)
 206 {
 207         struct inotify_event_private_data *event_priv;
 208
 209
 210         event_priv = container_of(fsn_event_priv, struct inotify_event_private_data,
 211                                   fsnotify_event_priv_data);
 212
 213         kmem_cache_free(event_priv_cachep, event_priv);
 214 }
 215
 216 const struct fsnotify_ops inotify_fsnotify_ops = {
 217         .handle_event = inotify_handle_event,
 218         .should_send_event = inotify_should_send_event,
 219         .free_group_priv = inotify_free_group_priv,
 220         .free_event_priv = inotify_free_event_priv,
 221         .freeing_mark = inotify_freeing_mark,
 222 };