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 #include <linux/writeback.h> /* for inode_lock */
  26
  27 #include <asm/atomic.h>
  28
  29 #include <linux/fsnotify_backend.h>
  30 #include "fsnotify.h"
  31
  32 /*
  33  * Recalculate the mask of events relevant to a given inode locked.
  34  */
  35 static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
  36 {
  37         struct fsnotify_mark *mark;
  38         struct hlist_node *pos;
  39         __u32 new_mask = 0;
  40
  41         assert_spin_locked(&inode->i_lock);
  42
  43         hlist_for_each_entry(mark, pos, &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         assert_spin_locked(&mark->lock);
  66         assert_spin_locked(&mark->group->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 *pos, *n;
  90         LIST_HEAD(free_list);
  91
  92         spin_lock(&inode->i_lock);
  93         hlist_for_each_entry_safe(mark, pos, 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                 fsnotify_destroy_mark(mark);
 102                 fsnotify_put_mark(mark);
 103         }
 104 }
 105
 106 /*
 107  * Given a group clear all of the inode marks associated with that group.
 108  */
 109 void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
 110 {
 111         fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
 112 }
 113
 114 /*
 115  * given a group and inode, find the mark associated with that combination.
 116  * if found take a reference to that mark and return it, else return NULL
 117  */
 118 struct fsnotify_mark *fsnotify_find_inode_mark_locked(struct fsnotify_group *group,
 119                                                       struct inode *inode)
 120 {
 121         struct fsnotify_mark *mark;
 122         struct hlist_node *pos;
 123
 124         assert_spin_locked(&inode->i_lock);
 125
 126         hlist_for_each_entry(mark, pos, &inode->i_fsnotify_marks, i.i_list) {
 127                 if (mark->group == group) {
 128                         fsnotify_get_mark(mark);
 129                         return mark;
 130                 }
 131         }
 132         return NULL;
 133 }
 134
 135 /*
 136  * given a group and inode, find the mark associated with that combination.
 137  * if found take a reference to that mark and return it, else return NULL
 138  */
 139 struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
 140                                                struct inode *inode)
 141 {
 142         struct fsnotify_mark *mark;
 143
 144         spin_lock(&inode->i_lock);
 145         mark = fsnotify_find_inode_mark_locked(group, inode);
 146         spin_unlock(&inode->i_lock);
 147
 148         return mark;
 149 }
 150
 151 /*
 152  * If we are setting a mark mask on an inode mark we should pin the inode
 153  * in memory.
 154  */
 155 void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
 156                                          __u32 mask)
 157 {
 158         struct inode *inode;
 159
 160         assert_spin_locked(&mark->lock);
 161
 162         if (mask &&
 163             mark->i.inode &&
 164             !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
 165                 mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
 166                 inode = igrab(mark->i.inode);
 167                 /*
 168                  * we shouldn't be able to get here if the inode wasn't
 169                  * already safely held in memory.  But bug in case it
 170                  * ever is wrong.
 171                  */
 172                 BUG_ON(!inode);
 173         }
 174 }
 175
 176 /*
 177  * Attach an initialized mark to a given inode.
 178  * These marks may be used for the fsnotify backend to determine which
 179  * event types should be delivered to which group and for which inodes.  These
 180  * marks are ordered according to priority, highest number first, and then by
 181  * the group's location in memory.
 182  */
 183 int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
 184                             struct fsnotify_group *group, struct inode *inode,
 185                             int allow_dups)
 186 {
 187         struct fsnotify_mark *lmark;
 188         struct hlist_node *node, *last = NULL;
 189         int ret = 0;
 190
 191         mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
 192
 193         assert_spin_locked(&mark->lock);
 194         assert_spin_locked(&group->mark_lock);
 195
 196         spin_lock(&inode->i_lock);
 197
 198         mark->i.inode = inode;
 199
 200         /* is mark the first mark? */
 201         if (hlist_empty(&inode->i_fsnotify_marks)) {
 202                 hlist_add_head_rcu(&mark->i.i_list, &inode->i_fsnotify_marks);
 203                 goto out;
 204         }
 205
 206         /* should mark be in the middle of the current list? */
 207         hlist_for_each_entry(lmark, node, &inode->i_fsnotify_marks, i.i_list) {
 208                 last = node;
 209
 210                 if ((lmark->group == group) && !allow_dups) {
 211                         ret = -EEXIST;
 212                         goto out;
 213                 }
 214
 215                 if (mark->group->priority < lmark->group->priority)
 216                         continue;
 217
 218                 if ((mark->group->priority == lmark->group->priority) &&
 219                     (mark->group < lmark->group))
 220                         continue;
 221
 222                 hlist_add_before_rcu(&mark->i.i_list, &lmark->i.i_list);
 223                 goto out;
 224         }
 225
 226         BUG_ON(last == NULL);
 227         /* mark should be the last entry.  last is the current last entry */
 228         hlist_add_after_rcu(last, &mark->i.i_list);
 229 out:
 230         fsnotify_recalc_inode_mask_locked(inode);
 231         spin_unlock(&inode->i_lock);
 232
 233         return ret;
 234 }
 235
 236 /**
 237  * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
 238  * @list: list of inodes being unmounted (sb->s_inodes)
 239  *
 240  * Called with inode_lock held, protecting the unmounting super block's list
 241  * of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
 242  * We temporarily drop inode_lock, however, 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_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_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.  Finally,
 299                  * iprune_mutex keeps shrink_icache_memory() away.
 300                  */
 301                 spin_unlock(&inode_lock);
 302
 303                 if (need_iput_tmp)
 304                         iput(need_iput_tmp);
 305
 306                 /* for each watch, send FS_UNMOUNT and then remove it */
 307                 fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
 308
 309                 fsnotify_inode_delete(inode);
 310
 311                 iput(inode);
 312
 313                 spin_lock(&inode_lock);
 314         }
 315         spin_unlock(&inode_lock);
 316 }