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
  27 #include <linux/atomic.h>
  28
  29 #include <linux/fsnotify_backend.h>
  30 #include "fsnotify.h"
  31 #include "../mount.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         struct mount *m = real_mount(mnt);
  38         LIST_HEAD(free_list);
  39
  40         spin_lock(&mnt->mnt_root->d_lock);
  41         hlist_for_each_entry_safe(mark, pos, n, &m->mnt_fsnotify_marks, m.m_list) {
  42                 list_add(&mark->m.free_m_list, &free_list);
  43                 hlist_del_init_rcu(&mark->m.m_list);
  44                 fsnotify_get_mark(mark);
  45         }
  46         spin_unlock(&mnt->mnt_root->d_lock);
  47
  48         list_for_each_entry_safe(mark, lmark, &free_list, m.free_m_list) {
  49                 fsnotify_destroy_mark(mark);
  50                 fsnotify_put_mark(mark);
  51         }
  52 }
  53
  54 void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
  55 {
  56         fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_VFSMOUNT);
  57 }
  58
  59 /*
  60  * Recalculate the mask of events relevant to a given vfsmount locked.
  61  */
  62 static void fsnotify_recalc_vfsmount_mask_locked(struct vfsmount *mnt)
  63 {
  64         struct mount *m = real_mount(mnt);
  65         struct fsnotify_mark *mark;
  66         struct hlist_node *pos;
  67         __u32 new_mask = 0;
  68
  69         assert_spin_locked(&mnt->mnt_root->d_lock);
  70
  71         hlist_for_each_entry(mark, pos, &m->mnt_fsnotify_marks, m.m_list)
  72                 new_mask |= mark->mask;
  73         m->mnt_fsnotify_mask = new_mask;
  74 }
  75
  76 /*
  77  * Recalculate the mnt->mnt_fsnotify_mask, or the mask of all FS_* event types
  78  * any notifier is interested in hearing for this mount point
  79  */
  80 void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt)
  81 {
  82         spin_lock(&mnt->mnt_root->d_lock);
  83         fsnotify_recalc_vfsmount_mask_locked(mnt);
  84         spin_unlock(&mnt->mnt_root->d_lock);
  85 }
  86
  87 void fsnotify_destroy_vfsmount_mark(struct fsnotify_mark *mark)
  88 {
  89         struct vfsmount *mnt = mark->m.mnt;
  90
  91         assert_spin_locked(&mark->lock);
  92         assert_spin_locked(&mark->group->mark_lock);
  93
  94         spin_lock(&mnt->mnt_root->d_lock);
  95
  96         hlist_del_init_rcu(&mark->m.m_list);
  97         mark->m.mnt = NULL;
  98
  99         fsnotify_recalc_vfsmount_mask_locked(mnt);
 100
 101         spin_unlock(&mnt->mnt_root->d_lock);
 102 }
 103
 104 static struct fsnotify_mark *fsnotify_find_vfsmount_mark_locked(struct fsnotify_group *group,
 105                                                                 struct vfsmount *mnt)
 106 {
 107         struct mount *m = real_mount(mnt);
 108         struct fsnotify_mark *mark;
 109         struct hlist_node *pos;
 110
 111         assert_spin_locked(&mnt->mnt_root->d_lock);
 112
 113         hlist_for_each_entry(mark, pos, &m->mnt_fsnotify_marks, m.m_list) {
 114                 if (mark->group == group) {
 115                         fsnotify_get_mark(mark);
 116                         return mark;
 117                 }
 118         }
 119         return NULL;
 120 }
 121
 122 /*
 123  * given a group and vfsmount, find the mark associated with that combination.
 124  * if found take a reference to that mark and return it, else return NULL
 125  */
 126 struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group,
 127                                                   struct vfsmount *mnt)
 128 {
 129         struct fsnotify_mark *mark;
 130
 131         spin_lock(&mnt->mnt_root->d_lock);
 132         mark = fsnotify_find_vfsmount_mark_locked(group, mnt);
 133         spin_unlock(&mnt->mnt_root->d_lock);
 134
 135         return mark;
 136 }
 137
 138 /*
 139  * Attach an initialized mark to a given group and vfsmount.
 140  * These marks may be used for the fsnotify backend to determine which
 141  * event types should be delivered to which groups.
 142  */
 143 int fsnotify_add_vfsmount_mark(struct fsnotify_mark *mark,
 144                                struct fsnotify_group *group, struct vfsmount *mnt,
 145                                int allow_dups)
 146 {
 147         struct mount *m = real_mount(mnt);
 148         struct fsnotify_mark *lmark;
 149         struct hlist_node *node, *last = NULL;
 150         int ret = 0;
 151
 152         mark->flags |= FSNOTIFY_MARK_FLAG_VFSMOUNT;
 153
 154         assert_spin_locked(&mark->lock);
 155         assert_spin_locked(&group->mark_lock);
 156
 157         spin_lock(&mnt->mnt_root->d_lock);
 158
 159         mark->m.mnt = mnt;
 160
 161         /* is mark the first mark? */
 162         if (hlist_empty(&m->mnt_fsnotify_marks)) {
 163                 hlist_add_head_rcu(&mark->m.m_list, &m->mnt_fsnotify_marks);
 164                 goto out;
 165         }
 166
 167         /* should mark be in the middle of the current list? */
 168         hlist_for_each_entry(lmark, node, &m->mnt_fsnotify_marks, m.m_list) {
 169                 last = node;
 170
 171                 if ((lmark->group == group) && !allow_dups) {
 172                         ret = -EEXIST;
 173                         goto out;
 174                 }
 175
 176                 if (mark->group->priority < lmark->group->priority)
 177                         continue;
 178
 179                 if ((mark->group->priority == lmark->group->priority) &&
 180                     (mark->group < lmark->group))
 181                         continue;
 182
 183                 hlist_add_before_rcu(&mark->m.m_list, &lmark->m.m_list);
 184                 goto out;
 185         }
 186
 187         BUG_ON(last == NULL);
 188         /* mark should be the last entry.  last is the current last entry */
 189         hlist_add_after_rcu(last, &mark->m.m_list);
 190 out:
 191         fsnotify_recalc_vfsmount_mask_locked(mnt);
 192         spin_unlock(&mnt->mnt_root->d_lock);
 193
 194         return ret;
 195 }