fs/notify/fsnotify.c

   1 /*
   2  *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
   3  *
   4  *  This program is free software; you can redistribute it and/or modify
   5  *  it under the terms of the GNU General Public License as published by
   6  *  the Free Software Foundation; either version 2, or (at your option)
   7  *  any later version.
   8  *
   9  *  This program is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *  GNU General Public License for more details.
  13  *
  14  *  You should have received a copy of the GNU General Public License
  15  *  along with this program; see the file COPYING.  If not, write to
  16  *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #include <linux/dcache.h>
  20 #include <linux/fs.h>
  21 #include <linux/gfp.h>
  22 #include <linux/init.h>
  23 #include <linux/module.h>
  24 #include <linux/mount.h>
  25 #include <linux/srcu.h>
  26
  27 #include <linux/fsnotify_backend.h>
  28 #include "fsnotify.h"
  29 #include "../mount.h"
  30
  31 /*
  32  * Clear all of the marks on an inode when it is being evicted from core
  33  */
  34 void __fsnotify_inode_delete(struct inode *inode)
  35 {
  36         fsnotify_clear_marks_by_inode(inode);
  37 }
  38 EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
  39
  40 void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
  41 {
  42         fsnotify_clear_marks_by_mount(mnt);
  43 }
  44
  45 /*
  46  * Given an inode, first check if we care what happens to our children.  Inotify
  47  * and dnotify both tell their parents about events.  If we care about any event
  48  * on a child we run all of our children and set a dentry flag saying that the
  49  * parent cares.  Thus when an event happens on a child it can quickly tell if
  50  * if there is a need to find a parent and send the event to the parent.
  51  */
  52 void __fsnotify_update_child_dentry_flags(struct inode *inode)
  53 {
  54         struct dentry *alias;
  55         int watched;
  56
  57         if (!S_ISDIR(inode->i_mode))
  58                 return;
  59
  60         /* determine if the children should tell inode about their events */
  61         watched = fsnotify_inode_watches_children(inode);
  62
  63         spin_lock(&inode->i_lock);
  64         /* run all of the dentries associated with this inode.  Since this is a
  65          * directory, there damn well better only be one item on this list */
  66         hlist_for_each_entry(alias, &inode->i_dentry, d_alias) {
  67                 struct dentry *child;
  68
  69                 /* run all of the children of the original inode and fix their
  70                  * d_flags to indicate parental interest (their parent is the
  71                  * original inode) */
  72                 spin_lock(&alias->d_lock);
  73                 list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
  74                         if (!child->d_inode)
  75                                 continue;
  76
  77                         spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
  78                         if (watched)
  79                                 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
  80                         else
  81                                 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
  82                         spin_unlock(&child->d_lock);
  83                 }
  84                 spin_unlock(&alias->d_lock);
  85         }
  86         spin_unlock(&inode->i_lock);
  87 }
  88
  89 /* Notify this dentry's parent about a child's events. */
  90 int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
  91 {
  92         struct dentry *parent;
  93         struct inode *p_inode;
  94         int ret = 0;
  95
  96         if (!dentry)
  97                 dentry = path->dentry;
  98
  99         if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
 100                 return 0;
 101
 102         parent = dget_parent(dentry);
 103         p_inode = parent->d_inode;
 104
 105         if (unlikely(!fsnotify_inode_watches_children(p_inode)))
 106                 __fsnotify_update_child_dentry_flags(p_inode);
 107         else if (p_inode->i_fsnotify_mask & mask) {
 108                 /* we are notifying a parent so come up with the new mask which
 109                  * specifies these are events which came from a child. */
 110                 mask |= FS_EVENT_ON_CHILD;
 111
 112                 if (path)
 113                         ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
 114                                        dentry->d_name.name, 0);
 115                 else
 116                         ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
 117                                        dentry->d_name.name, 0);
 118         }
 119
 120         dput(parent);
 121
 122         return ret;
 123 }
 124 EXPORT_SYMBOL_GPL(__fsnotify_parent);
 125
 126 static int send_to_group(struct inode *to_tell,
 127                          struct fsnotify_mark *inode_mark,
 128                          struct fsnotify_mark *vfsmount_mark,
 129                          __u32 mask, void *data,
 130                          int data_is, u32 cookie,
 131                          const unsigned char *file_name,
 132                          struct fsnotify_event **event)
 133 {
 134         struct fsnotify_group *group = NULL;
 135         __u32 inode_test_mask = 0;
 136         __u32 vfsmount_test_mask = 0;
 137
 138         if (unlikely(!inode_mark && !vfsmount_mark)) {
 139                 BUG();
 140                 return 0;
 141         }
 142
 143         /* clear ignored on inode modification */
 144         if (mask & FS_MODIFY) {
 145                 if (inode_mark &&
 146                     !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 147                         inode_mark->ignored_mask = 0;
 148                 if (vfsmount_mark &&
 149                     !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 150                         vfsmount_mark->ignored_mask = 0;
 151         }
 152
 153         /* does the inode mark tell us to do something? */
 154         if (inode_mark) {
 155                 group = inode_mark->group;
 156                 inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 157                 inode_test_mask &= inode_mark->mask;
 158                 inode_test_mask &= ~inode_mark->ignored_mask;
 159         }
 160
 161         /* does the vfsmount_mark tell us to do something? */
 162         if (vfsmount_mark) {
 163                 vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 164                 group = vfsmount_mark->group;
 165                 vfsmount_test_mask &= vfsmount_mark->mask;
 166                 vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
 167                 if (inode_mark)
 168                         vfsmount_test_mask &= ~inode_mark->ignored_mask;
 169         }
 170
 171         pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p"
 172                  " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
 173                  " data=%p data_is=%d cookie=%d event=%p\n",
 174                  __func__, group, to_tell, mask, inode_mark,
 175                  inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
 176                  data_is, cookie, *event);
 177
 178         if (!inode_test_mask && !vfsmount_test_mask)
 179                 return 0;
 180
 181         if (group->ops->should_send_event(group, to_tell, inode_mark,
 182                                           vfsmount_mark, mask, data,
 183                                           data_is) == false)
 184                 return 0;
 185
 186         if (!*event) {
 187                 *event = fsnotify_create_event(to_tell, mask, data,
 188                                                 data_is, file_name,
 189                                                 cookie, GFP_KERNEL);
 190                 if (!*event)
 191                         return -ENOMEM;
 192         }
 193         return group->ops->handle_event(group, inode_mark, vfsmount_mark, *event);
 194 }
 195
 196 /*
 197  * This is the main call to fsnotify.  The VFS calls into hook specific functions
 198  * in linux/fsnotify.h.  Those functions then in turn call here.  Here will call
 199  * out to all of the registered fsnotify_group.  Those groups can then use the
 200  * notification event in whatever means they feel necessary.
 201  */
 202 int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 203              const unsigned char *file_name, u32 cookie)
 204 {
 205         struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
 206         struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
 207         struct fsnotify_group *inode_group, *vfsmount_group;
 208         struct fsnotify_event *event = NULL;
 209         struct mount *mnt;
 210         int idx, ret = 0;
 211         /* global tests shouldn't care about events on child only the specific event */
 212         __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
 213
 214         if (data_is == FSNOTIFY_EVENT_PATH)
 215                 mnt = real_mount(((struct path *)data)->mnt);
 216         else
 217                 mnt = NULL;
 218
 219         /*
 220          * if this is a modify event we may need to clear the ignored masks
 221          * otherwise return if neither the inode nor the vfsmount care about
 222          * this type of event.
 223          */
 224         if (!(mask & FS_MODIFY) &&
 225             !(test_mask & to_tell->i_fsnotify_mask) &&
 226             !(mnt && test_mask & mnt->mnt_fsnotify_mask))
 227                 return 0;
 228
 229         idx = srcu_read_lock(&fsnotify_mark_srcu);
 230
 231         if ((mask & FS_MODIFY) ||
 232             (test_mask & to_tell->i_fsnotify_mask))
 233                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 234                                               &fsnotify_mark_srcu);
 235
 236         if (mnt && ((mask & FS_MODIFY) ||
 237                     (test_mask & mnt->mnt_fsnotify_mask))) {
 238                 vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
 239                                                  &fsnotify_mark_srcu);
 240                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 241                                               &fsnotify_mark_srcu);
 242         }
 243
 244         while (inode_node || vfsmount_node) {
 245                 inode_group = vfsmount_group = NULL;
 246
 247                 if (inode_node) {
 248                         inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
 249                                                  struct fsnotify_mark, i.i_list);
 250                         inode_group = inode_mark->group;
 251                 }
 252
 253                 if (vfsmount_node) {
 254                         vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
 255                                                         struct fsnotify_mark, m.m_list);
 256                         vfsmount_group = vfsmount_mark->group;
 257                 }
 258
 259                 if (inode_group > vfsmount_group) {
 260                         /* handle inode */
 261                         ret = send_to_group(to_tell, inode_mark, NULL, mask, data,
 262                                             data_is, cookie, file_name, &event);
 263                         /* we didn't use the vfsmount_mark */
 264                         vfsmount_group = NULL;
 265                 } else if (vfsmount_group > inode_group) {
 266                         ret = send_to_group(to_tell, NULL, vfsmount_mark, mask, data,
 267                                             data_is, cookie, file_name, &event);
 268                         inode_group = NULL;
 269                 } else {
 270                         ret = send_to_group(to_tell, inode_mark, vfsmount_mark,
 271                                             mask, data, data_is, cookie, file_name,
 272                                             &event);
 273                 }
 274
 275                 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
 276                         goto out;
 277
 278                 if (inode_group)
 279                         inode_node = srcu_dereference(inode_node->next,
 280                                                       &fsnotify_mark_srcu);
 281                 if (vfsmount_group)
 282                         vfsmount_node = srcu_dereference(vfsmount_node->next,
 283                                                          &fsnotify_mark_srcu);
 284         }
 285         ret = 0;
 286 out:
 287         srcu_read_unlock(&fsnotify_mark_srcu, idx);
 288         /*
 289          * fsnotify_create_event() took a reference so the event can't be cleaned
 290          * up while we are still trying to add it to lists, drop that one.
 291          */
 292         if (event)
 293                 fsnotify_put_event(event);
 294
 295         return ret;
 296 }
 297 EXPORT_SYMBOL_GPL(fsnotify);
 298
 299 static __init int fsnotify_init(void)
 300 {
 301         int ret;
 302
 303         BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
 304
 305         ret = init_srcu_struct(&fsnotify_mark_srcu);
 306         if (ret)
 307                 panic("initializing fsnotify_mark_srcu");
 308
 309         return 0;
 310 }
 311 core_initcall(fsnotify_init);