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/fs.h> /* struct inode */
  26 #include <linux/fsnotify_backend.h>
  27 #include <linux/inotify.h>
  28 #include <linux/path.h> /* struct path */
  29 #include <linux/slab.h> /* kmem_* */
  30 #include <linux/types.h>
  31
  32 #include "inotify.h"
  33
  34 /*
  35  * Check if 2 events contain the same information.  We do not compare private data
  36  * but at this moment that isn't a problem for any know fsnotify listeners.
  37  */
  38 static bool event_compare(struct fsnotify_event *old, struct fsnotify_event *new)
  39 {
  40         if ((old->mask == new->mask) &&
  41             (old->to_tell == new->to_tell) &&
  42             (old->data_type == new->data_type) &&
  43             (old->name_len == new->name_len)) {
  44                 switch (old->data_type) {
  45                 case (FSNOTIFY_EVENT_INODE):
  46                         /* remember, after old was put on the wait_q we aren't
  47                          * allowed to look at the inode any more, only thing
  48                          * left to check was if the file_name is the same */
  49                         if (old->name_len &&
  50                             !strcmp(old->file_name, new->file_name))
  51                                 return true;
  52                         break;
  53                 case (FSNOTIFY_EVENT_PATH):
  54                         if ((old->path.mnt == new->path.mnt) &&
  55                             (old->path.dentry == new->path.dentry))
  56                                 return true;
  57                         break;
  58                 case (FSNOTIFY_EVENT_NONE):
  59                         if (old->mask & FS_Q_OVERFLOW)
  60                                 return true;
  61                         else if (old->mask & FS_IN_IGNORED)
  62                                 return false;
  63                         return true;
  64                 };
  65         }
  66         return false;
  67 }
  68
  69 static int inotify_merge(struct list_head *list, struct fsnotify_event *event)
  70 {
  71         struct fsnotify_event_holder *last_holder;
  72         struct fsnotify_event *last_event;
  73         int ret = 0;
  74
  75         /* and the list better be locked by something too */
  76         spin_lock(&event->lock);
  77
  78         last_holder = list_entry(list->prev, struct fsnotify_event_holder, event_list);
  79         last_event = last_holder->event;
  80         if (event_compare(last_event, event))
  81                 ret = -EEXIST;
  82
  83         spin_unlock(&event->lock);
  84
  85         return ret;
  86 }
  87
  88 static int inotify_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
  89 {
  90         struct fsnotify_mark_entry *entry;
  91         struct inotify_inode_mark_entry *ientry;
  92         struct inode *to_tell;
  93         struct inotify_event_private_data *event_priv;
  94         struct fsnotify_event_private_data *fsn_event_priv;
  95         int wd, ret;
  96
  97         to_tell = event->to_tell;
  98
  99         spin_lock(&to_tell->i_lock);
 100         entry = fsnotify_find_mark_entry(group, to_tell);
 101         spin_unlock(&to_tell->i_lock);
 102         /* race with watch removal?  We already passes should_send */
 103         if (unlikely(!entry))
 104                 return 0;
 105         ientry = container_of(entry, struct inotify_inode_mark_entry,
 106                               fsn_entry);
 107         wd = ientry->wd;
 108
 109         event_priv = kmem_cache_alloc(event_priv_cachep, GFP_KERNEL);
 110         if (unlikely(!event_priv))
 111                 return -ENOMEM;
 112
 113         fsn_event_priv = &event_priv->fsnotify_event_priv_data;
 114
 115         fsn_event_priv->group = group;
 116         event_priv->wd = wd;
 117
 118         ret = fsnotify_add_notify_event(group, event, fsn_event_priv, inotify_merge);
 119         if (ret) {
 120                 inotify_free_event_priv(fsn_event_priv);
 121                 /* EEXIST says we tail matched, EOVERFLOW isn't something
 122                  * to report up the stack. */
 123                 if ((ret == -EEXIST) ||
 124                     (ret == -EOVERFLOW))
 125                         ret = 0;
 126         }
 127
 128         /*
 129          * If we hold the entry until after the event is on the queue
 130          * IN_IGNORED won't be able to pass this event in the queue
 131          */
 132         fsnotify_put_mark(entry);
 133
 134         return ret;
 135 }
 136
 137 static void inotify_freeing_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group)
 138 {
 139         inotify_ignored_and_remove_idr(entry, group);
 140 }
 141
 142 static bool inotify_should_send_event(struct fsnotify_group *group, struct inode *inode,
 143                                       __u32 mask, void *data, int data_type)
 144 {
 145         struct fsnotify_mark_entry *entry;
 146         bool send;
 147
 148         spin_lock(&inode->i_lock);
 149         entry = fsnotify_find_mark_entry(group, inode);
 150         spin_unlock(&inode->i_lock);
 151         if (!entry)
 152                 return false;
 153
 154         mask = (mask & ~FS_EVENT_ON_CHILD);
 155         send = (entry->mask & mask);
 156
 157         /* find took a reference */
 158         fsnotify_put_mark(entry);
 159
 160         return send;
 161 }
 162
 163 /*
 164  * This is NEVER supposed to be called.  Inotify marks should either have been
 165  * removed from the idr when the watch was removed or in the
 166  * fsnotify_destroy_mark_by_group() call when the inotify instance was being
 167  * torn down.  This is only called if the idr is about to be freed but there
 168  * are still marks in it.
 169  */
 170 static int idr_callback(int id, void *p, void *data)
 171 {
 172         struct fsnotify_mark_entry *entry;
 173         struct inotify_inode_mark_entry *ientry;
 174         static bool warned = false;
 175
 176         if (warned)
 177                 return 0;
 178
 179         warned = false;
 180         entry = p;
 181         ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry);
 182
 183         WARN(1, "inotify closing but id=%d for entry=%p in group=%p still in "
 184                 "idr.  Probably leaking memory\n", id, p, data);
 185
 186         /*
 187          * I'm taking the liberty of assuming that the mark in question is a
 188          * valid address and I'm dereferencing it.  This might help to figure
 189          * out why we got here and the panic is no worse than the original
 190          * BUG() that was here.
 191          */
 192         if (entry)
 193                 printk(KERN_WARNING "entry->group=%p inode=%p wd=%d\n",
 194                         entry->group, entry->inode, ientry->wd);
 195         return 0;
 196 }
 197
 198 static void inotify_free_group_priv(struct fsnotify_group *group)
 199 {
 200         /* ideally the idr is empty and we won't hit the BUG in teh callback */
 201         idr_for_each(&group->inotify_data.idr, idr_callback, group);
 202         idr_remove_all(&group->inotify_data.idr);
 203         idr_destroy(&group->inotify_data.idr);
 204 }
 205
 206 void inotify_free_event_priv(struct fsnotify_event_private_data *fsn_event_priv)
 207 {
 208         struct inotify_event_private_data *event_priv;
 209
 210
 211         event_priv = container_of(fsn_event_priv, struct inotify_event_private_data,
 212                                   fsnotify_event_priv_data);
 213
 214         kmem_cache_free(event_priv_cachep, event_priv);
 215 }
 216
 217 const struct fsnotify_ops inotify_fsnotify_ops = {
 218         .handle_event = inotify_handle_event,
 219         .should_send_event = inotify_should_send_event,
 220         .free_group_priv = inotify_free_group_priv,
 221         .free_event_priv = inotify_free_event_priv,
 222         .freeing_mark = inotify_freeing_mark,
 223 };