linux/fs/notify/fsnotify.c
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   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 */
  34void __fsnotify_inode_delete(struct inode *inode)
  35{
  36        fsnotify_clear_marks_by_inode(inode);
  37}
  38EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
  39
  40void __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 */
  52void __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. */
  91int __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}
 125EXPORT_SYMBOL_GPL(__fsnotify_parent);
 126
 127static 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 */
 203int 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;
 287out:
 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}
 298EXPORT_SYMBOL_GPL(fsnotify);
 299
 300static __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}
 312core_initcall(fsnotify_init);
 313
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