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_u.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_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 {
 133         struct fsnotify_group *group = NULL;
 134         __u32 inode_test_mask = 0;
 135         __u32 vfsmount_test_mask = 0;
 136
 137         if (unlikely(!inode_mark && !vfsmount_mark)) {
 138                 BUG();
 139                 return 0;
 140         }
 141
 142         /* clear ignored on inode modification */
 143         if (mask & FS_MODIFY) {
 144                 if (inode_mark &&
 145                     !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 146                         inode_mark->ignored_mask = 0;
 147                 if (vfsmount_mark &&
 148                     !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 149                         vfsmount_mark->ignored_mask = 0;
 150         }
 151
 152         /* does the inode mark tell us to do something? */
 153         if (inode_mark) {
 154                 group = inode_mark->group;
 155                 inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 156                 inode_test_mask &= inode_mark->mask;
 157                 inode_test_mask &= ~inode_mark->ignored_mask;
 158         }
 159
 160         /* does the vfsmount_mark tell us to do something? */
 161         if (vfsmount_mark) {
 162                 vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 163                 group = vfsmount_mark->group;
 164                 vfsmount_test_mask &= vfsmount_mark->mask;
 165                 vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
 166                 if (inode_mark)
 167                         vfsmount_test_mask &= ~inode_mark->ignored_mask;
 168         }
 169
 170         pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p"
 171                  " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
 172                  " data=%p data_is=%d cookie=%d\n",
 173                  __func__, group, to_tell, mask, inode_mark,
 174                  inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
 175                  data_is, cookie);
 176
 177         if (!inode_test_mask && !vfsmount_test_mask)
 178                 return 0;
 179
 180         return group->ops->handle_event(group, to_tell, inode_mark,
 181                                         vfsmount_mark, mask, data, data_is,
 182                                         file_name, cookie);
 183 }
 184
 185 /*
 186  * This is the main call to fsnotify.  The VFS calls into hook specific functions
 187  * in linux/fsnotify.h.  Those functions then in turn call here.  Here will call
 188  * out to all of the registered fsnotify_group.  Those groups can then use the
 189  * notification event in whatever means they feel necessary.
 190  */
 191 int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 192              const unsigned char *file_name, u32 cookie)
 193 {
 194         struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
 195         struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
 196         struct fsnotify_group *inode_group, *vfsmount_group;
 197         struct mount *mnt;
 198         int idx, ret = 0;
 199         /* global tests shouldn't care about events on child only the specific event */
 200         __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
 201
 202         if (data_is == FSNOTIFY_EVENT_PATH)
 203                 mnt = real_mount(((struct path *)data)->mnt);
 204         else
 205                 mnt = NULL;
 206
 207         /*
 208          * if this is a modify event we may need to clear the ignored masks
 209          * otherwise return if neither the inode nor the vfsmount care about
 210          * this type of event.
 211          */
 212         if (!(mask & FS_MODIFY) &&
 213             !(test_mask & to_tell->i_fsnotify_mask) &&
 214             !(mnt && test_mask & mnt->mnt_fsnotify_mask))
 215                 return 0;
 216
 217         idx = srcu_read_lock(&fsnotify_mark_srcu);
 218
 219         if ((mask & FS_MODIFY) ||
 220             (test_mask & to_tell->i_fsnotify_mask))
 221                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 222                                               &fsnotify_mark_srcu);
 223
 224         if (mnt && ((mask & FS_MODIFY) ||
 225                     (test_mask & mnt->mnt_fsnotify_mask))) {
 226                 vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
 227                                                  &fsnotify_mark_srcu);
 228                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 229                                               &fsnotify_mark_srcu);
 230         }
 231
 232         /*
 233          * We need to merge inode & vfsmount mark lists so that inode mark
 234          * ignore masks are properly reflected for mount mark notifications.
 235          * That's why this traversal is so complicated...
 236          */
 237         while (inode_node || vfsmount_node) {
 238                 inode_group = NULL;
 239                 inode_mark = NULL;
 240                 vfsmount_group = NULL;
 241                 vfsmount_mark = NULL;
 242
 243                 if (inode_node) {
 244                         inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
 245                                                  struct fsnotify_mark, obj_list);
 246                         inode_group = inode_mark->group;
 247                 }
 248
 249                 if (vfsmount_node) {
 250                         vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
 251                                                     struct fsnotify_mark, obj_list);
 252                         vfsmount_group = vfsmount_mark->group;
 253                 }
 254
 255                 if (inode_group && vfsmount_group) {
 256                         int cmp = fsnotify_compare_groups(inode_group,
 257                                                           vfsmount_group);
 258                         if (cmp > 0) {
 259                                 inode_group = NULL;
 260                                 inode_mark = NULL;
 261                         } else if (cmp < 0) {
 262                                 vfsmount_group = NULL;
 263                                 vfsmount_mark = NULL;
 264                         }
 265                 }
 266                 ret = send_to_group(to_tell, inode_mark, vfsmount_mark, mask,
 267                                     data, data_is, cookie, file_name);
 268
 269                 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
 270                         goto out;
 271
 272                 if (inode_group)
 273                         inode_node = srcu_dereference(inode_node->next,
 274                                                       &fsnotify_mark_srcu);
 275                 if (vfsmount_group)
 276                         vfsmount_node = srcu_dereference(vfsmount_node->next,
 277                                                          &fsnotify_mark_srcu);
 278         }
 279         ret = 0;
 280 out:
 281         srcu_read_unlock(&fsnotify_mark_srcu, idx);
 282
 283         return ret;
 284 }
 285 EXPORT_SYMBOL_GPL(fsnotify);
 286
 287 static __init int fsnotify_init(void)
 288 {
 289         int ret;
 290
 291         BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
 292
 293         ret = init_srcu_struct(&fsnotify_mark_srcu);
 294         if (ret)
 295                 panic("initializing fsnotify_mark_srcu");
 296
 297         return 0;
 298 }
 299 core_initcall(fsnotify_init);