fs/notify/inode_mark.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/fs.h>
  20 #include <linux/init.h>
  21 #include <linux/kernel.h>
  22 #include <linux/module.h>
  23 #include <linux/mutex.h>
  24 #include <linux/spinlock.h>
  25
  26 #include <linux/atomic.h>
  27
  28 #include <linux/fsnotify_backend.h>
  29 #include "fsnotify.h"
  30
  31 #include "../internal.h"
  32
  33 /*
  34  * Recalculate the mask of events relevant to a given inode locked.
  35  */
  36 static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
  37 {
  38         struct fsnotify_mark *mark;
  39         __u32 new_mask = 0;
  40
  41         assert_spin_locked(&inode->i_lock);
  42
  43         hlist_for_each_entry(mark, &inode->i_fsnotify_marks, i.i_list)
  44                 new_mask |= mark->mask;
  45         inode->i_fsnotify_mask = new_mask;
  46 }
  47
  48 /*
  49  * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
  50  * any notifier is interested in hearing for this inode.
  51  */
  52 void fsnotify_recalc_inode_mask(struct inode *inode)
  53 {
  54         spin_lock(&inode->i_lock);
  55         fsnotify_recalc_inode_mask_locked(inode);
  56         spin_unlock(&inode->i_lock);
  57
  58         __fsnotify_update_child_dentry_flags(inode);
  59 }
  60
  61 void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
  62 {
  63         struct inode *inode = mark->i.inode;
  64
  65         BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
  66         assert_spin_locked(&mark->lock);
  67
  68         spin_lock(&inode->i_lock);
  69
  70         hlist_del_init_rcu(&mark->i.i_list);
  71         mark->i.inode = NULL;
  72
  73         /*
  74          * this mark is now off the inode->i_fsnotify_marks list and we
  75          * hold the inode->i_lock, so this is the perfect time to update the
  76          * inode->i_fsnotify_mask
  77          */
  78         fsnotify_recalc_inode_mask_locked(inode);
  79
  80         spin_unlock(&inode->i_lock);
  81 }
  82
  83 /*
  84  * Given an inode, destroy all of the marks associated with that inode.
  85  */
  86 void fsnotify_clear_marks_by_inode(struct inode *inode)
  87 {
  88         struct fsnotify_mark *mark, *lmark;
  89         struct hlist_node *n;
  90         LIST_HEAD(free_list);
  91
  92         spin_lock(&inode->i_lock);
  93         hlist_for_each_entry_safe(mark, n, &inode->i_fsnotify_marks, i.i_list) {
  94                 list_add(&mark->i.free_i_list, &free_list);
  95                 hlist_del_init_rcu(&mark->i.i_list);
  96                 fsnotify_get_mark(mark);
  97         }
  98         spin_unlock(&inode->i_lock);
  99
 100         list_for_each_entry_safe(mark, lmark, &free_list, i.free_i_list) {
 101                 struct fsnotify_group *group;
 102
 103                 spin_lock(&mark->lock);
 104                 fsnotify_get_group(mark->group);
 105                 group = mark->group;
 106                 spin_unlock(&mark->lock);
 107
 108                 fsnotify_destroy_mark(mark, group);
 109                 fsnotify_put_mark(mark);
 110                 fsnotify_put_group(group);
 111         }
 112 }
 113
 114 /*
 115  * Given a group clear all of the inode marks associated with that group.
 116  */
 117 void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
 118 {
 119         fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
 120 }
 121
 122 /*
 123  * given a group and inode, find the mark associated with that combination.
 124  * if found take a reference to that mark and return it, else return NULL
 125  */
 126 static struct fsnotify_mark *fsnotify_find_inode_mark_locked(
 127                 struct fsnotify_group *group,
 128                 struct inode *inode)
 129 {
 130         struct fsnotify_mark *mark;
 131
 132         assert_spin_locked(&inode->i_lock);
 133
 134         hlist_for_each_entry(mark, &inode->i_fsnotify_marks, i.i_list) {
 135                 if (mark->group == group) {
 136                         fsnotify_get_mark(mark);
 137                         return mark;
 138                 }
 139         }
 140         return NULL;
 141 }
 142
 143 /*
 144  * given a group and inode, find the mark associated with that combination.
 145  * if found take a reference to that mark and return it, else return NULL
 146  */
 147 struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
 148                                                struct inode *inode)
 149 {
 150         struct fsnotify_mark *mark;
 151
 152         spin_lock(&inode->i_lock);
 153         mark = fsnotify_find_inode_mark_locked(group, inode);
 154         spin_unlock(&inode->i_lock);
 155
 156         return mark;
 157 }
 158
 159 /*
 160  * If we are setting a mark mask on an inode mark we should pin the inode
 161  * in memory.
 162  */
 163 void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
 164                                          __u32 mask)
 165 {
 166         struct inode *inode;
 167
 168         assert_spin_locked(&mark->lock);
 169
 170         if (mask &&
 171             mark->i.inode &&
 172             !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
 173                 mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
 174                 inode = igrab(mark->i.inode);
 175                 /*
 176                  * we shouldn't be able to get here if the inode wasn't
 177                  * already safely held in memory.  But bug in case it
 178                  * ever is wrong.
 179                  */
 180                 BUG_ON(!inode);
 181         }
 182 }
 183
 184 /*
 185  * Attach an initialized mark to a given inode.
 186  * These marks may be used for the fsnotify backend to determine which
 187  * event types should be delivered to which group and for which inodes.  These
 188  * marks are ordered according to priority, highest number first, and then by
 189  * the group's location in memory.
 190  */
 191 int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
 192                             struct fsnotify_group *group, struct inode *inode,
 193                             int allow_dups)
 194 {
 195         struct fsnotify_mark *lmark, *last = NULL;
 196         int ret = 0;
 197
 198         mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
 199
 200         BUG_ON(!mutex_is_locked(&group->mark_mutex));
 201         assert_spin_locked(&mark->lock);
 202
 203         spin_lock(&inode->i_lock);
 204
 205         mark->i.inode = inode;
 206
 207         /* is mark the first mark? */
 208         if (hlist_empty(&inode->i_fsnotify_marks)) {
 209                 hlist_add_head_rcu(&mark->i.i_list, &inode->i_fsnotify_marks);
 210                 goto out;
 211         }
 212
 213         /* should mark be in the middle of the current list? */
 214         hlist_for_each_entry(lmark, &inode->i_fsnotify_marks, i.i_list) {
 215                 last = lmark;
 216
 217                 if ((lmark->group == group) && !allow_dups) {
 218                         ret = -EEXIST;
 219                         goto out;
 220                 }
 221
 222                 if (mark->group->priority < lmark->group->priority)
 223                         continue;
 224
 225                 if ((mark->group->priority == lmark->group->priority) &&
 226                     (mark->group < lmark->group))
 227                         continue;
 228
 229                 hlist_add_before_rcu(&mark->i.i_list, &lmark->i.i_list);
 230                 goto out;
 231         }
 232
 233         BUG_ON(last == NULL);
 234         /* mark should be the last entry.  last is the current last entry */
 235         hlist_add_after_rcu(&last->i.i_list, &mark->i.i_list);
 236 out:
 237         fsnotify_recalc_inode_mask_locked(inode);
 238         spin_unlock(&inode->i_lock);
 239
 240         return ret;
 241 }
 242
 243 /**
 244  * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
 245  * @list: list of inodes being unmounted (sb->s_inodes)
 246  *
 247  * Called during unmount with no locks held, so needs to be safe against
 248  * concurrent modifiers. We temporarily drop inode_sb_list_lock and CAN block.
 249  */
 250 void fsnotify_unmount_inodes(struct list_head *list)
 251 {
 252         struct inode *inode, *next_i, *need_iput = NULL;
 253
 254         spin_lock(&inode_sb_list_lock);
 255         list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
 256                 struct inode *need_iput_tmp;
 257
 258                 /*
 259                  * We cannot __iget() an inode in state I_FREEING,
 260                  * I_WILL_FREE, or I_NEW which is fine because by that point
 261                  * the inode cannot have any associated watches.
 262                  */
 263                 spin_lock(&inode->i_lock);
 264                 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
 265                         spin_unlock(&inode->i_lock);
 266                         continue;
 267                 }
 268
 269                 /*
 270                  * If i_count is zero, the inode cannot have any watches and
 271                  * doing an __iget/iput with MS_ACTIVE clear would actually
 272                  * evict all inodes with zero i_count from icache which is
 273                  * unnecessarily violent and may in fact be illegal to do.
 274                  */
 275                 if (!atomic_read(&inode->i_count)) {
 276                         spin_unlock(&inode->i_lock);
 277                         continue;
 278                 }
 279
 280                 need_iput_tmp = need_iput;
 281                 need_iput = NULL;
 282
 283                 /* In case fsnotify_inode_delete() drops a reference. */
 284                 if (inode != need_iput_tmp)
 285                         __iget(inode);
 286                 else
 287                         need_iput_tmp = NULL;
 288                 spin_unlock(&inode->i_lock);
 289
 290                 /* In case the dropping of a reference would nuke next_i. */
 291                 while (&next_i->i_sb_list != list) {
 292                         spin_lock(&next_i->i_lock);
 293                         if (!(next_i->i_state & (I_FREEING | I_WILL_FREE)) &&
 294                                                 atomic_read(&next_i->i_count)) {
 295                                 __iget(next_i);
 296                                 need_iput = next_i;
 297                                 spin_unlock(&next_i->i_lock);
 298                                 break;
 299                         }
 300                         spin_unlock(&next_i->i_lock);
 301                         next_i = list_entry(next_i->i_sb_list.next,
 302                                                 struct inode, i_sb_list);
 303                 }
 304
 305                 /*
 306                  * We can safely drop inode_sb_list_lock here because either
 307                  * we actually hold references on both inode and next_i or
 308                  * end of list.  Also no new inodes will be added since the
 309                  * umount has begun.
 310                  */
 311                 spin_unlock(&inode_sb_list_lock);
 312
 313                 if (need_iput_tmp)
 314                         iput(need_iput_tmp);
 315
 316                 /* for each watch, send FS_UNMOUNT and then remove it */
 317                 fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
 318
 319                 fsnotify_inode_delete(inode);
 320
 321                 iput(inode);
 322
 323                 spin_lock(&inode_sb_list_lock);
 324         }
 325         spin_unlock(&inode_sb_list_lock);
 326 }