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