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_FILE):
  56                         if ((old->file->f_path.mnt == new->file->f_path.mnt) &&
  57                             (old->file->f_path.dentry == new->file->f_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, struct fsnotify_event *event)
  93 {
  94         struct fsnotify_mark *fsn_mark;
  95         struct inotify_inode_mark *i_mark;
  96         struct inode *to_tell;
  97         struct inotify_event_private_data *event_priv;
  98         struct fsnotify_event_private_data *fsn_event_priv;
  99         struct fsnotify_event *added_event;
 100         int wd, ret = 0;
 101
 102         pr_debug("%s: group=%p event=%p to_tell=%p mask=%x\n", __func__, group,
 103                  event, event->to_tell, event->mask);
 104
 105         to_tell = event->to_tell;
 106
 107         fsn_mark = fsnotify_find_inode_mark(group, to_tell);
 108         /* race with watch removal?  We already passes should_send */
 109         if (unlikely(!fsn_mark))
 110                 return 0;
 111         i_mark = container_of(fsn_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 (fsn_mark->mask & IN_ONESHOT)
 134                 fsnotify_destroy_mark(fsn_mark);
 135
 136         /*
 137          * If we hold the fsn_mark until after the event is on the queue
 138          * IN_IGNORED won't be able to pass this event in the queue
 139          */
 140         fsnotify_put_mark(fsn_mark);
 141
 142         return ret;
 143 }
 144
 145 static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
 146 {
 147         inotify_ignored_and_remove_idr(fsn_mark, group);
 148 }
 149
 150 static bool inotify_should_send_event(struct fsnotify_group *group, struct inode *inode,
 151                                       struct vfsmount *mnt, __u32 mask, void *data,
 152                                       int data_type)
 153 {
 154         struct fsnotify_mark *fsn_mark;
 155         bool send;
 156
 157         pr_debug("%s: group=%p inode=%p mask=%x data=%p data_type=%d\n",
 158                  __func__, group, inode, mask, data, data_type);
 159
 160         fsn_mark = fsnotify_find_inode_mark(group, inode);
 161         if (!fsn_mark)
 162                 return false;
 163
 164         mask = (mask & ~FS_EVENT_ON_CHILD);
 165         send = (fsn_mark->mask & mask);
 166
 167         if (send && (fsn_mark->mask & FS_EXCL_UNLINK) &&
 168             (data_type == FSNOTIFY_EVENT_FILE)) {
 169                 struct file *file  = data;
 170
 171                 if (d_unlinked(file->f_path.dentry))
 172                         send = false;
 173         }
 174
 175         /* find took a reference */
 176         fsnotify_put_mark(fsn_mark);
 177
 178         return send;
 179 }
 180
 181 /*
 182  * This is NEVER supposed to be called.  Inotify marks should either have been
 183  * removed from the idr when the watch was removed or in the
 184  * fsnotify_destroy_mark_by_group() call when the inotify instance was being
 185  * torn down.  This is only called if the idr is about to be freed but there
 186  * are still marks in it.
 187  */
 188 static int idr_callback(int id, void *p, void *data)
 189 {
 190         struct fsnotify_mark *fsn_mark;
 191         struct inotify_inode_mark *i_mark;
 192         static bool warned = false;
 193
 194         if (warned)
 195                 return 0;
 196
 197         warned = true;
 198         fsn_mark = p;
 199         i_mark = container_of(fsn_mark, struct inotify_inode_mark, fsn_mark);
 200
 201         WARN(1, "inotify closing but id=%d for fsn_mark=%p in group=%p still in "
 202                 "idr.  Probably leaking memory\n", id, p, data);
 203
 204         /*
 205          * I'm taking the liberty of assuming that the mark in question is a
 206          * valid address and I'm dereferencing it.  This might help to figure
 207          * out why we got here and the panic is no worse than the original
 208          * BUG() that was here.
 209          */
 210         if (fsn_mark)
 211                 printk(KERN_WARNING "fsn_mark->group=%p inode=%p wd=%d\n",
 212                         fsn_mark->group, fsn_mark->i.inode, i_mark->wd);
 213         return 0;
 214 }
 215
 216 static void inotify_free_group_priv(struct fsnotify_group *group)
 217 {
 218         /* ideally the idr is empty and we won't hit the BUG in teh callback */
 219         idr_for_each(&group->inotify_data.idr, idr_callback, group);
 220         idr_remove_all(&group->inotify_data.idr);
 221         idr_destroy(&group->inotify_data.idr);
 222         free_uid(group->inotify_data.user);
 223 }
 224
 225 void inotify_free_event_priv(struct fsnotify_event_private_data *fsn_event_priv)
 226 {
 227         struct inotify_event_private_data *event_priv;
 228
 229
 230         event_priv = container_of(fsn_event_priv, struct inotify_event_private_data,
 231                                   fsnotify_event_priv_data);
 232
 233         kmem_cache_free(event_priv_cachep, event_priv);
 234 }
 235
 236 const struct fsnotify_ops inotify_fsnotify_ops = {
 237         .handle_event = inotify_handle_event,
 238         .should_send_event = inotify_should_send_event,
 239         .free_group_priv = inotify_free_group_priv,
 240         .free_event_priv = inotify_free_event_priv,
 241         .freeing_mark = inotify_freeing_mark,
 242 };