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
  30 /*
  31  * Clear all of the marks on an inode when it is being evicted from core
  32  */
  33 void __fsnotify_inode_delete(struct inode *inode)
  34 {
  35         fsnotify_clear_marks_by_inode(inode);
  36 }
  37 EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
  38
  39 void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
  40 {
  41         fsnotify_clear_marks_by_mount(mnt);
  42 }
  43
  44 /*
  45  * Given an inode, first check if we care what happens to our children.  Inotify
  46  * and dnotify both tell their parents about events.  If we care about any event
  47  * on a child we run all of our children and set a dentry flag saying that the
  48  * parent cares.  Thus when an event happens on a child it can quickly tell if
  49  * if there is a need to find a parent and send the event to the parent.
  50  */
  51 void __fsnotify_update_child_dentry_flags(struct inode *inode)
  52 {
  53         struct dentry *alias;
  54         int watched;
  55
  56         if (!S_ISDIR(inode->i_mode))
  57                 return;
  58
  59         /* determine if the children should tell inode about their events */
  60         watched = fsnotify_inode_watches_children(inode);
  61
  62         spin_lock(&dcache_inode_lock);
  63         /* run all of the dentries associated with this inode.  Since this is a
  64          * directory, there damn well better only be one item on this list */
  65         list_for_each_entry(alias, &inode->i_dentry, d_alias) {
  66                 struct dentry *child;
  67
  68                 /* run all of the children of the original inode and fix their
  69                  * d_flags to indicate parental interest (their parent is the
  70                  * original inode) */
  71                 spin_lock(&alias->d_lock);
  72                 list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
  73                         if (!child->d_inode)
  74                                 continue;
  75
  76                         spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
  77                         if (watched)
  78                                 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
  79                         else
  80                                 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
  81                         spin_unlock(&child->d_lock);
  82                 }
  83                 spin_unlock(&alias->d_lock);
  84         }
  85         spin_unlock(&dcache_inode_lock);
  86 }
  87
  88 /* Notify this dentry's parent about a child's events. */
  89 int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
  90 {
  91         struct dentry *parent;
  92         struct inode *p_inode;
  93         int ret = 0;
  94
  95         if (!dentry)
  96                 dentry = path->dentry;
  97
  98         if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
  99                 return 0;
 100
 101         parent = dget_parent(dentry);
 102         p_inode = parent->d_inode;
 103
 104         if (unlikely(!fsnotify_inode_watches_children(p_inode)))
 105                 __fsnotify_update_child_dentry_flags(p_inode);
 106         else if (p_inode->i_fsnotify_mask & mask) {
 107                 /* we are notifying a parent so come up with the new mask which
 108                  * specifies these are events which came from a child. */
 109                 mask |= FS_EVENT_ON_CHILD;
 110
 111                 if (path)
 112                         ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
 113                                        dentry->d_name.name, 0);
 114                 else
 115                         ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
 116                                        dentry->d_name.name, 0);
 117         }
 118
 119         dput(parent);
 120
 121         return ret;
 122 }
 123 EXPORT_SYMBOL_GPL(__fsnotify_parent);
 124
 125 static int send_to_group(struct inode *to_tell, struct vfsmount *mnt,
 126                          struct fsnotify_mark *inode_mark,
 127                          struct fsnotify_mark *vfsmount_mark,
 128                          __u32 mask, void *data,
 129                          int data_is, u32 cookie,
 130                          const unsigned char *file_name,
 131                          struct fsnotify_event **event)
 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 mnt=%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 event=%p\n",
 173                  __func__, group, to_tell, mnt, mask, inode_mark,
 174                  inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
 175                  data_is, cookie, *event);
 176
 177         if (!inode_test_mask && !vfsmount_test_mask)
 178                 return 0;
 179
 180         if (group->ops->should_send_event(group, to_tell, inode_mark,
 181                                           vfsmount_mark, mask, data,
 182                                           data_is) == false)
 183                 return 0;
 184
 185         if (!*event) {
 186                 *event = fsnotify_create_event(to_tell, mask, data,
 187                                                 data_is, file_name,
 188                                                 cookie, GFP_KERNEL);
 189                 if (!*event)
 190                         return -ENOMEM;
 191         }
 192         return group->ops->handle_event(group, inode_mark, vfsmount_mark, *event);
 193 }
 194
 195 /*
 196  * This is the main call to fsnotify.  The VFS calls into hook specific functions
 197  * in linux/fsnotify.h.  Those functions then in turn call here.  Here will call
 198  * out to all of the registered fsnotify_group.  Those groups can then use the
 199  * notification event in whatever means they feel necessary.
 200  */
 201 int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 202              const unsigned char *file_name, u32 cookie)
 203 {
 204         struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
 205         struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
 206         struct fsnotify_group *inode_group, *vfsmount_group;
 207         struct fsnotify_event *event = NULL;
 208         struct vfsmount *mnt;
 209         int idx, ret = 0;
 210         /* global tests shouldn't care about events on child only the specific event */
 211         __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
 212
 213         if (data_is == FSNOTIFY_EVENT_PATH)
 214                 mnt = ((struct path *)data)->mnt;
 215         else
 216                 mnt = NULL;
 217
 218         /*
 219          * if this is a modify event we may need to clear the ignored masks
 220          * otherwise return if neither the inode nor the vfsmount care about
 221          * this type of event.
 222          */
 223         if (!(mask & FS_MODIFY) &&
 224             !(test_mask & to_tell->i_fsnotify_mask) &&
 225             !(mnt && test_mask & mnt->mnt_fsnotify_mask))
 226                 return 0;
 227
 228         idx = srcu_read_lock(&fsnotify_mark_srcu);
 229
 230         if ((mask & FS_MODIFY) ||
 231             (test_mask & to_tell->i_fsnotify_mask))
 232                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 233                                               &fsnotify_mark_srcu);
 234
 235         if (mnt && ((mask & FS_MODIFY) ||
 236                     (test_mask & mnt->mnt_fsnotify_mask))) {
 237                 vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
 238                                                  &fsnotify_mark_srcu);
 239                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 240                                               &fsnotify_mark_srcu);
 241         }
 242
 243         while (inode_node || vfsmount_node) {
 244                 inode_group = vfsmount_group = NULL;
 245
 246                 if (inode_node) {
 247                         inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
 248                                                  struct fsnotify_mark, i.i_list);
 249                         inode_group = inode_mark->group;
 250                 }
 251
 252                 if (vfsmount_node) {
 253                         vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
 254                                                         struct fsnotify_mark, m.m_list);
 255                         vfsmount_group = vfsmount_mark->group;
 256                 }
 257
 258                 if (inode_group > vfsmount_group) {
 259                         /* handle inode */
 260                         ret = send_to_group(to_tell, NULL, inode_mark, NULL, mask, data,
 261                                             data_is, cookie, file_name, &event);
 262                         /* we didn't use the vfsmount_mark */
 263                         vfsmount_group = NULL;
 264                 } else if (vfsmount_group > inode_group) {
 265                         ret = send_to_group(to_tell, mnt, NULL, vfsmount_mark, mask, data,
 266                                             data_is, cookie, file_name, &event);
 267                         inode_group = NULL;
 268                 } else {
 269                         ret = send_to_group(to_tell, mnt, inode_mark, vfsmount_mark,
 270                                             mask, data, data_is, cookie, file_name,
 271                                             &event);
 272                 }
 273
 274                 if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
 275                         goto out;
 276
 277                 if (inode_group)
 278                         inode_node = srcu_dereference(inode_node->next,
 279                                                       &fsnotify_mark_srcu);
 280                 if (vfsmount_group)
 281                         vfsmount_node = srcu_dereference(vfsmount_node->next,
 282                                                          &fsnotify_mark_srcu);
 283         }
 284         ret = 0;
 285 out:
 286         srcu_read_unlock(&fsnotify_mark_srcu, idx);
 287         /*
 288          * fsnotify_create_event() took a reference so the event can't be cleaned
 289          * up while we are still trying to add it to lists, drop that one.
 290          */
 291         if (event)
 292                 fsnotify_put_event(event);
 293
 294         return ret;
 295 }
 296 EXPORT_SYMBOL_GPL(fsnotify);
 297
 298 static __init int fsnotify_init(void)
 299 {
 300         int ret;
 301
 302         BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
 303
 304         ret = init_srcu_struct(&fsnotify_mark_srcu);
 305         if (ret)
 306                 panic("initializing fsnotify_mark_srcu");
 307
 308         return 0;
 309 }
 310 core_initcall(fsnotify_init);