fs/notify/vfsmount_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/mount.h>
  24 #include <linux/mutex.h>
  25 #include <linux/spinlock.h>
  26 #include <linux/writeback.h> /* for inode_lock */
  27
  28 #include <asm/atomic.h>
  29
  30 #include <linux/fsnotify_backend.h>
  31 #include "fsnotify.h"
  32
  33 void fsnotify_clear_marks_by_mount(struct vfsmount *mnt)
  34 {
  35         struct fsnotify_mark *mark, *lmark;
  36         struct hlist_node *pos, *n;
  37         LIST_HEAD(free_list);
  38
  39         spin_lock(&mnt->mnt_root->d_lock);
  40         hlist_for_each_entry_safe(mark, pos, n, &mnt->mnt_fsnotify_marks, m.m_list) {
  41                 list_add(&mark->m.free_m_list, &free_list);
  42                 hlist_del_init_rcu(&mark->m.m_list);
  43                 fsnotify_get_mark(mark);
  44         }
  45         spin_unlock(&mnt->mnt_root->d_lock);
  46
  47         list_for_each_entry_safe(mark, lmark, &free_list, m.free_m_list) {
  48                 fsnotify_destroy_mark(mark);
  49                 fsnotify_put_mark(mark);
  50         }
  51 }
  52
  53 void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
  54 {
  55         fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_VFSMOUNT);
  56 }
  57
  58 /*
  59  * Recalculate the mask of events relevant to a given vfsmount locked.
  60  */
  61 static void fsnotify_recalc_vfsmount_mask_locked(struct vfsmount *mnt)
  62 {
  63         struct fsnotify_mark *mark;
  64         struct hlist_node *pos;
  65         __u32 new_mask = 0;
  66
  67         assert_spin_locked(&mnt->mnt_root->d_lock);
  68
  69         hlist_for_each_entry(mark, pos, &mnt->mnt_fsnotify_marks, m.m_list)
  70                 new_mask |= mark->mask;
  71         mnt->mnt_fsnotify_mask = new_mask;
  72 }
  73
  74 /*
  75  * Recalculate the mnt->mnt_fsnotify_mask, or the mask of all FS_* event types
  76  * any notifier is interested in hearing for this mount point
  77  */
  78 void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt)
  79 {
  80         spin_lock(&mnt->mnt_root->d_lock);
  81         fsnotify_recalc_vfsmount_mask_locked(mnt);
  82         spin_unlock(&mnt->mnt_root->d_lock);
  83 }
  84
  85 void fsnotify_destroy_vfsmount_mark(struct fsnotify_mark *mark)
  86 {
  87         struct vfsmount *mnt = mark->m.mnt;
  88
  89         assert_spin_locked(&mark->lock);
  90         assert_spin_locked(&mark->group->mark_lock);
  91
  92         spin_lock(&mnt->mnt_root->d_lock);
  93
  94         hlist_del_init_rcu(&mark->m.m_list);
  95         mark->m.mnt = NULL;
  96
  97         fsnotify_recalc_vfsmount_mask_locked(mnt);
  98
  99         spin_unlock(&mnt->mnt_root->d_lock);
 100 }
 101
 102 static struct fsnotify_mark *fsnotify_find_vfsmount_mark_locked(struct fsnotify_group *group,
 103                                                                 struct vfsmount *mnt)
 104 {
 105         struct fsnotify_mark *mark;
 106         struct hlist_node *pos;
 107
 108         assert_spin_locked(&mnt->mnt_root->d_lock);
 109
 110         hlist_for_each_entry(mark, pos, &mnt->mnt_fsnotify_marks, m.m_list) {
 111                 if (mark->group == group) {
 112                         fsnotify_get_mark(mark);
 113                         return mark;
 114                 }
 115         }
 116         return NULL;
 117 }
 118
 119 /*
 120  * given a group and vfsmount, find the mark associated with that combination.
 121  * if found take a reference to that mark and return it, else return NULL
 122  */
 123 struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group,
 124                                                   struct vfsmount *mnt)
 125 {
 126         struct fsnotify_mark *mark;
 127
 128         spin_lock(&mnt->mnt_root->d_lock);
 129         mark = fsnotify_find_vfsmount_mark_locked(group, mnt);
 130         spin_unlock(&mnt->mnt_root->d_lock);
 131
 132         return mark;
 133 }
 134
 135 /*
 136  * Attach an initialized mark to a given group and vfsmount.
 137  * These marks may be used for the fsnotify backend to determine which
 138  * event types should be delivered to which groups.
 139  */
 140 int fsnotify_add_vfsmount_mark(struct fsnotify_mark *mark,
 141                                struct fsnotify_group *group, struct vfsmount *mnt,
 142                                int allow_dups)
 143 {
 144         struct fsnotify_mark *lmark;
 145         struct hlist_node *node, *last = NULL;
 146         int ret = 0;
 147
 148         mark->flags |= FSNOTIFY_MARK_FLAG_VFSMOUNT;
 149
 150         assert_spin_locked(&mark->lock);
 151         assert_spin_locked(&group->mark_lock);
 152
 153         spin_lock(&mnt->mnt_root->d_lock);
 154
 155         mark->m.mnt = mnt;
 156
 157         /* is mark the first mark? */
 158         if (hlist_empty(&mnt->mnt_fsnotify_marks)) {
 159                 hlist_add_head_rcu(&mark->m.m_list, &mnt->mnt_fsnotify_marks);
 160                 goto out;
 161         }
 162
 163         /* should mark be in the middle of the current list? */
 164         hlist_for_each_entry(lmark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
 165                 last = node;
 166
 167                 if ((lmark->group == group) && !allow_dups) {
 168                         ret = -EEXIST;
 169                         goto out;
 170                 }
 171
 172                 if (mark->group->priority < lmark->group->priority)
 173                         continue;
 174
 175                 if ((mark->group->priority == lmark->group->priority) &&
 176                     (mark->group < lmark->group))
 177                         continue;
 178
 179                 hlist_add_before_rcu(&mark->m.m_list, &lmark->m.m_list);
 180                 goto out;
 181         }
 182
 183         BUG_ON(last == NULL);
 184         /* mark should be the last entry.  last is the current last entry */
 185         hlist_add_after_rcu(last, &mark->m.m_list);
 186 out:
 187         fsnotify_recalc_vfsmount_mask_locked(mnt);
 188         spin_unlock(&mnt->mnt_root->d_lock);
 189
 190         return ret;
 191 }