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 inode->i_fsnotify_mask, or the mask of all FS_* event types
  35  * any notifier is interested in hearing for this inode.
  36  */
  37 void fsnotify_recalc_inode_mask(struct inode *inode)
  38 {
  39         spin_lock(&inode->i_lock);
  40         inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
  41         spin_unlock(&inode->i_lock);
  42
  43         __fsnotify_update_child_dentry_flags(inode);
  44 }
  45
  46 void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
  47 {
  48         struct inode *inode = mark->inode;
  49
  50         BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
  51         assert_spin_locked(&mark->lock);
  52
  53         spin_lock(&inode->i_lock);
  54
  55         hlist_del_init_rcu(&mark->obj_list);
  56         mark->inode = NULL;
  57
  58         /*
  59          * this mark is now off the inode->i_fsnotify_marks list and we
  60          * hold the inode->i_lock, so this is the perfect time to update the
  61          * inode->i_fsnotify_mask
  62          */
  63         inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
  64         spin_unlock(&inode->i_lock);
  65 }
  66
  67 /*
  68  * Given a group clear all of the inode marks associated with that group.
  69  */
  70 void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
  71 {
  72         fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
  73 }
  74
  75 /*
  76  * given a group and inode, find the mark associated with that combination.
  77  * if found take a reference to that mark and return it, else return NULL
  78  */
  79 struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
  80                                                struct inode *inode)
  81 {
  82         struct fsnotify_mark *mark;
  83
  84         spin_lock(&inode->i_lock);
  85         mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
  86         spin_unlock(&inode->i_lock);
  87
  88         return mark;
  89 }
  90
  91 /*
  92  * If we are setting a mark mask on an inode mark we should pin the inode
  93  * in memory.
  94  */
  95 void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
  96                                          __u32 mask)
  97 {
  98         struct inode *inode;
  99
 100         assert_spin_locked(&mark->lock);
 101
 102         if (mask &&
 103             mark->inode &&
 104             !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
 105                 mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
 106                 inode = igrab(mark->inode);
 107                 /*
 108                  * we shouldn't be able to get here if the inode wasn't
 109                  * already safely held in memory.  But bug in case it
 110                  * ever is wrong.
 111                  */
 112                 BUG_ON(!inode);
 113         }
 114 }
 115
 116 /*
 117  * Attach an initialized mark to a given inode.
 118  * These marks may be used for the fsnotify backend to determine which
 119  * event types should be delivered to which group and for which inodes.  These
 120  * marks are ordered according to priority, highest number first, and then by
 121  * the group's location in memory.
 122  */
 123 int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
 124                             struct fsnotify_group *group, struct inode *inode,
 125                             int allow_dups)
 126 {
 127         int ret;
 128
 129         mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
 130
 131         BUG_ON(!mutex_is_locked(&group->mark_mutex));
 132         assert_spin_locked(&mark->lock);
 133
 134         spin_lock(&inode->i_lock);
 135         mark->inode = inode;
 136         ret = fsnotify_add_mark_list(&inode->i_fsnotify_marks, mark,
 137                                      allow_dups);
 138         inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
 139         spin_unlock(&inode->i_lock);
 140
 141         return ret;
 142 }
 143
 144 /**
 145  * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
 146  * @sb: superblock being unmounted.
 147  *
 148  * Called during unmount with no locks held, so needs to be safe against
 149  * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
 150  */
 151 void fsnotify_unmount_inodes(struct super_block *sb)
 152 {
 153         struct inode *inode, *next_i, *need_iput = NULL;
 154
 155         spin_lock(&sb->s_inode_list_lock);
 156         list_for_each_entry_safe(inode, next_i, &sb->s_inodes, i_sb_list) {
 157                 struct inode *need_iput_tmp;
 158
 159                 /*
 160                  * We cannot __iget() an inode in state I_FREEING,
 161                  * I_WILL_FREE, or I_NEW which is fine because by that point
 162                  * the inode cannot have any associated watches.
 163                  */
 164                 spin_lock(&inode->i_lock);
 165                 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
 166                         spin_unlock(&inode->i_lock);
 167                         continue;
 168                 }
 169
 170                 /*
 171                  * If i_count is zero, the inode cannot have any watches and
 172                  * doing an __iget/iput with MS_ACTIVE clear would actually
 173                  * evict all inodes with zero i_count from icache which is
 174                  * unnecessarily violent and may in fact be illegal to do.
 175                  */
 176                 if (!atomic_read(&inode->i_count)) {
 177                         spin_unlock(&inode->i_lock);
 178                         continue;
 179                 }
 180
 181                 need_iput_tmp = need_iput;
 182                 need_iput = NULL;
 183
 184                 /* In case fsnotify_inode_delete() drops a reference. */
 185                 if (inode != need_iput_tmp)
 186                         __iget(inode);
 187                 else
 188                         need_iput_tmp = NULL;
 189                 spin_unlock(&inode->i_lock);
 190
 191                 /* In case the dropping of a reference would nuke next_i. */
 192                 while (&next_i->i_sb_list != &sb->s_inodes) {
 193                         spin_lock(&next_i->i_lock);
 194                         if (!(next_i->i_state & (I_FREEING | I_WILL_FREE)) &&
 195                                                 atomic_read(&next_i->i_count)) {
 196                                 __iget(next_i);
 197                                 need_iput = next_i;
 198                                 spin_unlock(&next_i->i_lock);
 199                                 break;
 200                         }
 201                         spin_unlock(&next_i->i_lock);
 202                         next_i = list_next_entry(next_i, i_sb_list);
 203                 }
 204
 205                 /*
 206                  * We can safely drop s_inode_list_lock here because either
 207                  * we actually hold references on both inode and next_i or
 208                  * end of list.  Also no new inodes will be added since the
 209                  * umount has begun.
 210                  */
 211                 spin_unlock(&sb->s_inode_list_lock);
 212
 213                 if (need_iput_tmp)
 214                         iput(need_iput_tmp);
 215
 216                 /* for each watch, send FS_UNMOUNT and then remove it */
 217                 fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
 218
 219                 fsnotify_inode_delete(inode);
 220
 221                 iput(inode);
 222
 223                 spin_lock(&sb->s_inode_list_lock);
 224         }
 225         spin_unlock(&sb->s_inode_list_lock);
 226 }