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_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                 list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
  72                         if (!child->d_inode)
  73                                 continue;
  74
  75                         spin_lock(&child->d_lock);
  76                         if (watched)
  77                                 child->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
  78                         else
  79                                 child->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
  80                         spin_unlock(&child->d_lock);
  81                 }
  82         }
  83         spin_unlock(&dcache_lock);
  84 }
  85
  86 /* Notify this dentry's parent about a child's events. */
  87 void __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)
  88 {
  89         struct dentry *parent;
  90         struct inode *p_inode;
  91         bool send = false;
  92         bool should_update_children = false;
  93
  94         if (!dentry)
  95                 dentry = path->dentry;
  96
  97         if (!(dentry->d_flags & DCACHE_FSNOTIFY_PARENT_WATCHED))
  98                 return;
  99
 100         spin_lock(&dentry->d_lock);
 101         parent = dentry->d_parent;
 102         p_inode = parent->d_inode;
 103
 104         if (fsnotify_inode_watches_children(p_inode)) {
 105                 if (p_inode->i_fsnotify_mask & mask) {
 106                         dget(parent);
 107                         send = true;
 108                 }
 109         } else {
 110                 /*
 111                  * The parent doesn't care about events on it's children but
 112                  * at least one child thought it did.  We need to run all the
 113                  * children and update their d_flags to let them know p_inode
 114                  * doesn't care about them any more.
 115                  */
 116                 dget(parent);
 117                 should_update_children = true;
 118         }
 119
 120         spin_unlock(&dentry->d_lock);
 121
 122         if (send) {
 123                 /* we are notifying a parent so come up with the new mask which
 124                  * specifies these are events which came from a child. */
 125                 mask |= FS_EVENT_ON_CHILD;
 126
 127                 if (path)
 128                         fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
 129                                  dentry->d_name.name, 0);
 130                 else
 131                         fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
 132                                  dentry->d_name.name, 0);
 133                 dput(parent);
 134         }
 135
 136         if (unlikely(should_update_children)) {
 137                 __fsnotify_update_child_dentry_flags(p_inode);
 138                 dput(parent);
 139         }
 140 }
 141 EXPORT_SYMBOL_GPL(__fsnotify_parent);
 142
 143 static int send_to_group(struct inode *to_tell, struct vfsmount *mnt,
 144                          struct fsnotify_mark *inode_mark,
 145                          struct fsnotify_mark *vfsmount_mark,
 146                          __u32 mask, void *data,
 147                          int data_is, u32 cookie,
 148                          const unsigned char *file_name,
 149                          struct fsnotify_event **event)
 150 {
 151         struct fsnotify_group *group = NULL;
 152         __u32 inode_test_mask = 0;
 153         __u32 vfsmount_test_mask = 0;
 154
 155         if (unlikely(!inode_mark && !vfsmount_mark)) {
 156                 BUG();
 157                 return 0;
 158         }
 159
 160         /* clear ignored on inode modification */
 161         if (mask & FS_MODIFY) {
 162                 if (inode_mark &&
 163                     !(inode_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 164                         inode_mark->ignored_mask = 0;
 165                 if (vfsmount_mark &&
 166                     !(vfsmount_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
 167                         vfsmount_mark->ignored_mask = 0;
 168         }
 169
 170         /* does the inode mark tell us to do something? */
 171         if (inode_mark) {
 172                 group = inode_mark->group;
 173                 inode_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 174                 inode_test_mask &= inode_mark->mask;
 175                 inode_test_mask &= ~inode_mark->ignored_mask;
 176         }
 177
 178         /* does the vfsmount_mark tell us to do something? */
 179         if (vfsmount_mark) {
 180                 vfsmount_test_mask = (mask & ~FS_EVENT_ON_CHILD);
 181                 group = vfsmount_mark->group;
 182                 vfsmount_test_mask &= vfsmount_mark->mask;
 183                 vfsmount_test_mask &= ~vfsmount_mark->ignored_mask;
 184                 if (inode_mark)
 185                         vfsmount_test_mask &= ~inode_mark->ignored_mask;
 186         }
 187
 188         pr_debug("%s: group=%p to_tell=%p mnt=%p mask=%x inode_mark=%p"
 189                  " inode_test_mask=%x vfsmount_mark=%p vfsmount_test_mask=%x"
 190                  " data=%p data_is=%d cookie=%d event=%p\n",
 191                  __func__, group, to_tell, mnt, mask, inode_mark,
 192                  inode_test_mask, vfsmount_mark, vfsmount_test_mask, data,
 193                  data_is, cookie, *event);
 194
 195         if (!inode_test_mask && !vfsmount_test_mask)
 196                 return 0;
 197
 198         if (group->ops->should_send_event(group, to_tell, inode_mark,
 199                                           vfsmount_mark, mask, data,
 200                                           data_is) == false)
 201                 return 0;
 202
 203         if (!*event) {
 204                 *event = fsnotify_create_event(to_tell, mask, data,
 205                                                 data_is, file_name,
 206                                                 cookie, GFP_KERNEL);
 207                 if (!*event)
 208                         return -ENOMEM;
 209         }
 210         return group->ops->handle_event(group, inode_mark, vfsmount_mark, *event);
 211 }
 212
 213 /*
 214  * This is the main call to fsnotify.  The VFS calls into hook specific functions
 215  * in linux/fsnotify.h.  Those functions then in turn call here.  Here will call
 216  * out to all of the registered fsnotify_group.  Those groups can then use the
 217  * notification event in whatever means they feel necessary.
 218  */
 219 int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
 220              const unsigned char *file_name, u32 cookie)
 221 {
 222         struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
 223         struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
 224         struct fsnotify_group *inode_group, *vfsmount_group;
 225         struct fsnotify_event *event = NULL;
 226         struct vfsmount *mnt;
 227         int idx, ret = 0;
 228         /* global tests shouldn't care about events on child only the specific event */
 229         __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);
 230
 231         if (data_is == FSNOTIFY_EVENT_PATH)
 232                 mnt = ((struct path *)data)->mnt;
 233         else
 234                 mnt = NULL;
 235
 236         /*
 237          * if this is a modify event we may need to clear the ignored masks
 238          * otherwise return if neither the inode nor the vfsmount care about
 239          * this type of event.
 240          */
 241         if (!(mask & FS_MODIFY) &&
 242             !(test_mask & to_tell->i_fsnotify_mask) &&
 243             !(mnt && test_mask & mnt->mnt_fsnotify_mask))
 244                 return 0;
 245
 246         idx = srcu_read_lock(&fsnotify_mark_srcu);
 247
 248         if ((mask & FS_MODIFY) ||
 249             (test_mask & to_tell->i_fsnotify_mask))
 250                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 251                                               &fsnotify_mark_srcu);
 252
 253         if (mnt && ((mask & FS_MODIFY) ||
 254                     (test_mask & mnt->mnt_fsnotify_mask))) {
 255                 vfsmount_node = srcu_dereference(mnt->mnt_fsnotify_marks.first,
 256                                                  &fsnotify_mark_srcu);
 257                 inode_node = srcu_dereference(to_tell->i_fsnotify_marks.first,
 258                                               &fsnotify_mark_srcu);
 259         }
 260
 261         while (inode_node || vfsmount_node) {
 262                 inode_group = vfsmount_group = NULL;
 263
 264                 if (inode_node) {
 265                         inode_mark = hlist_entry(srcu_dereference(inode_node, &fsnotify_mark_srcu),
 266                                                  struct fsnotify_mark, i.i_list);
 267                         inode_group = inode_mark->group;
 268                 }
 269
 270                 if (vfsmount_node) {
 271                         vfsmount_mark = hlist_entry(srcu_dereference(vfsmount_node, &fsnotify_mark_srcu),
 272                                                         struct fsnotify_mark, m.m_list);
 273                         vfsmount_group = vfsmount_mark->group;
 274                 }
 275
 276                 if (inode_group > vfsmount_group) {
 277                         /* handle inode */
 278                         send_to_group(to_tell, NULL, inode_mark, NULL, mask, data,
 279                                       data_is, cookie, file_name, &event);
 280                         /* we didn't use the vfsmount_mark */
 281                         vfsmount_group = NULL;
 282                 } else if (vfsmount_group > inode_group) {
 283                         send_to_group(to_tell, mnt, NULL, vfsmount_mark, mask, data,
 284                                       data_is, cookie, file_name, &event);
 285                         inode_group = NULL;
 286                 } else {
 287                         send_to_group(to_tell, mnt, inode_mark, vfsmount_mark,
 288                                       mask, data, data_is, cookie, file_name,
 289                                       &event);
 290                 }
 291
 292                 if (inode_group)
 293                         inode_node = srcu_dereference(inode_node->next,
 294                                                       &fsnotify_mark_srcu);
 295                 if (vfsmount_group)
 296                         vfsmount_node = srcu_dereference(vfsmount_node->next,
 297                                                          &fsnotify_mark_srcu);
 298         }
 299
 300         srcu_read_unlock(&fsnotify_mark_srcu, idx);
 301         /*
 302          * fsnotify_create_event() took a reference so the event can't be cleaned
 303          * up while we are still trying to add it to lists, drop that one.
 304          */
 305         if (event)
 306                 fsnotify_put_event(event);
 307
 308         return ret;
 309 }
 310 EXPORT_SYMBOL_GPL(fsnotify);
 311
 312 static __init int fsnotify_init(void)
 313 {
 314         int ret;
 315
 316         BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
 317
 318         ret = init_srcu_struct(&fsnotify_mark_srcu);
 319         if (ret)
 320                 panic("initializing fsnotify_mark_srcu");
 321
 322         return 0;
 323 }
 324 core_initcall(fsnotify_init);