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         struct hlist_node *p;
  56         int watched;
  57
  58         if (!S_ISDIR(inode->i_mode))
  59                 return;
  60
  61         /* determine if the children should tell inode about their events */
  62         watched = fsnotify_inode_watches_children(inode);
  63
  64         spin_lock(&inode->i_lock);
  65         /* run all of the dentries associated with this inode.  Since this is a
  66          * directory, there damn well better only be one item on this list */
  67         hlist_for_each_entry(alias, p, &inode->i_dentry, d_alias) {
  68                 struct dentry *child;
  69
  70                 /* run all of the children of the original inode and fix their
  71                  * d_flags to indicate parental interest (their parent is the
  72                  * original inode) */
  73                 spin_lock(&alias->d_lock);
  74                 list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
  75                         if (!child->d_inode)
  76                                 continue;
  77
  78                         spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
  79                         if (watched)
  80                                 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
  81                         else
  82                                 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
  83                         spin_unlock(&child->d_lock);
  84                 }
  85                 spin_unlock(&alias->d_lock);
  86         }
  87         spin_unlock(&inode->i_lock);
  88 }
  89
  90 /* Notify this dentry's parent about a child's events. */
  91 int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
  92 {
  93         struct dentry *parent;
  94         struct inode *p_inode;
  95         int ret = 0;
  96
  97         if (!dentry)
  98                 dentry = path->dentry;
  99
 100         if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
 101                 return 0;
 102
 103         parent = dget_parent(dentry);
 104         p_inode = parent->d_inode;
 105
 106         if (unlikely(!fsnotify_inode_watches_children(p_inode)))
 107                 __fsnotify_update_child_dentry_flags(p_inode);
 108         else if (p_inode->i_fsnotify_mask & mask) {
 109                 /* we are notifying a parent so come up with the new mask which
 110                  * specifies these are events which came from a child. */
 111                 mask |= FS_EVENT_ON_CHILD;
 112
 113                 if (path)
 114                         ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
 115                                        dentry->d_name.name, 0);
 116                 else
 117                         ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
 118                                        dentry->d_name.name, 0);
 119         }
 120
 121         dput(parent);
 122
 123         return ret;
 124 }
 125 EXPORT_SYMBOL_GPL(__fsnotify_parent);
 126
 127 static int send_to_group(struct inode *to_tell,
 128                          struct fsnotify_mark *inode_mark,
 129                          struct fsnotify_mark *vfsmount_mark,
 130                          __u32 mask, void *data,
 131                          int data_is, u32 cookie,
 132                          const unsigned char *file_name,
 133                          struct fsnotify_event **event)
 134 {
 135         struct fsnotify_group *group = NULL;
 136         __u32 inode_test_mask = 0;
 137         __u32 vfsmount_test_mask = 0;
 138
 139         if (unlikely(!inode_mark && !vfsmount_mark)) {
 140                 BUG();
 141                 return 0;
 142         }
 143
 144         /* clear ignored on inode modification */
 145         if (mask & FS_MODIFY) {
 146                 if (inode_mark &&
 147                     !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 148                         inode_mark->ignored_mask = 0;
 149                 if (vfsmount_mark &&
 150                     !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 151                         vfsmount_mark->ignored_mask = 0;
 152         }
 153
 154         /* does the inode mark tell us to do something? */
 155         if (inode_mark) {
 156                 group = inode_mark->group;
 157                 inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 158                 inode_test_mask &= inode_mark->mask;
 159                 inode_test_mask &= ~inode_mark->ignored_mask;
 160         }
 161
 162         /* does the vfsmount_mark tell us to do something? */
 163         if (vfsmount_mark) {
 164                 vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 165                 group = vfsmount_mark->group;
 166                 vfsmount_test_mask &= vfsmount_mark->mask;
 167                 vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
 168                 if (inode_mark)
 169                         vfsmount_test_mask &= ~inode_mark->ignored_mask;
 170         }
 171
 172         pr_debug("%s: group=%p to_tell=%p mask=%x inode_mark=%p"
 173                  " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
 174                  " data=%p data_is=%d cookie=%d event=%p\n",
 175                  __func__, group, to_tell, mask, inode_mark,
 176                  inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
 177                  data_is, cookie, *event);
 178
 179         if (!inode_test_mask && !vfsmount_test_mask)
 180                 return 0;
 181
 182         if (group->ops->should_send_event(group, to_tell, inode_mark,
 183                                           vfsmount_mark, mask, data,
 184                                           data_is) == false)
 185                 return 0;
 186
 187         if (!*event) {
 188                 *event = fsnotify_create_event(to_tell, mask, data,
 189                                                 data_is, file_name,
 190                                                 cookie, GFP_KERNEL);
 191                 if (!*event)
 192                         return -ENOMEM;
 193         }
 194         return group->ops->handle_event(group, inode_mark, vfsmount_mark, *event);
 195 }
 196
 197 /*
 198  * This is the main call to fsnotify.  The VFS calls into hook specific functions
 199  * in linux/fsnotify.h.  Those functions then in turn call here.  Here will call
 200  * out to all of the registered fsnotify_group.  Those groups can then use the
 201  * notification event in whatever means they feel necessary.
 202  */
 203 int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 204              const unsigned char *file_name, u32 cookie)
 205 {
 206         struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
 207         struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
 208         struct fsnotify_group *inode_group, *vfsmount_group;
 209         struct fsnotify_event *event = NULL;
 210         struct mount *mnt;
 211         int idx, ret = 0;
 212         /* global tests shouldn't care about events on child only the specific event */
 213         __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
 214
 215         if (data_is == FSNOTIFY_EVENT_PATH)
 216                 mnt = real_mount(((struct path *)data)->mnt);
 217         else
 218                 mnt = NULL;
 219
 220         /*
 221          * if this is a modify event we may need to clear the ignored masks
 222          * otherwise return if neither the inode nor the vfsmount care about
 223          * this type of event.
 224          */
 225         if (!(mask & FS_MODIFY) &&
 226             !(test_mask & to_tell->i_fsnotify_mask) &&
 227             !(mnt && test_mask & mnt->mnt_fsnotify_mask))
 228                 return 0;
 229
 230         idx = srcu_read_lock(&fsnotify_mark_srcu);
 231
 232         if ((mask & FS_MODIFY) ||
 233             (test_mask & to_tell->i_fsnotify_mask))
 234                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 235                                               &fsnotify_mark_srcu);
 236
 237         if (mnt && ((mask & FS_MODIFY) ||
 238                     (test_mask & mnt->mnt_fsnotify_mask))) {
 239                 vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
 240                                                  &fsnotify_mark_srcu);
 241                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 242                                               &fsnotify_mark_srcu);
 243         }
 244
 245         while (inode_node || vfsmount_node) {
 246                 inode_group = vfsmount_group = NULL;
 247
 248                 if (inode_node) {
 249                         inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
 250                                                  struct fsnotify_mark, i.i_list);
 251                         inode_group = inode_mark->group;
 252                 }
 253
 254                 if (vfsmount_node) {
 255                         vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
 256                                                         struct fsnotify_mark, m.m_list);
 257                         vfsmount_group = vfsmount_mark->group;
 258                 }
 259
 260                 if (inode_group > vfsmount_group) {
 261                         /* handle inode */
 262                         ret = send_to_group(to_tell, inode_mark, NULL, mask, data,
 263                                             data_is, cookie, file_name, &event);
 264                         /* we didn't use the vfsmount_mark */
 265                         vfsmount_group = NULL;
 266                 } else if (vfsmount_group > inode_group) {
 267                         ret = send_to_group(to_tell, NULL, vfsmount_mark, mask, data,
 268                                             data_is, cookie, file_name, &event);
 269                         inode_group = NULL;
 270                 } else {
 271                         ret = send_to_group(to_tell, inode_mark, vfsmount_mark,
 272                                             mask, data, data_is, cookie, file_name,
 273                                             &event);
 274                 }
 275
 276                 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
 277                         goto out;
 278
 279                 if (inode_group)
 280                         inode_node = srcu_dereference(inode_node->next,
 281                                                       &fsnotify_mark_srcu);
 282                 if (vfsmount_group)
 283                         vfsmount_node = srcu_dereference(vfsmount_node->next,
 284                                                          &fsnotify_mark_srcu);
 285         }
 286         ret = 0;
 287 out:
 288         srcu_read_unlock(&fsnotify_mark_srcu, idx);
 289         /*
 290          * fsnotify_create_event() took a reference so the event can't be cleaned
 291          * up while we are still trying to add it to lists, drop that one.
 292          */
 293         if (event)
 294                 fsnotify_put_event(event);
 295
 296         return ret;
 297 }
 298 EXPORT_SYMBOL_GPL(fsnotify);
 299
 300 static __init int fsnotify_init(void)
 301 {
 302         int ret;
 303
 304         BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
 305
 306         ret = init_srcu_struct(&fsnotify_mark_srcu);
 307         if (ret)
 308                 panic("initializing fsnotify_mark_srcu");
 309
 310         return 0;
 311 }
 312 core_initcall(fsnotify_init);