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 *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, 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                 struct fsnotify_group *group;
  50
  51                 spin_lock(&mark->lock);
  52                 fsnotify_get_group(mark->group);
  53                 group = mark->group;
  54                 spin_unlock(&mark->lock);
  55
  56                 fsnotify_destroy_mark(mark, group);
  57                 fsnotify_put_mark(mark);
  58                 fsnotify_put_group(group);
  59         }
  60 }
  61
  62 void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
  63 {
  64         fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_VFSMOUNT);
  65 }
  66
  67 /*
  68  * Recalculate the mask of events relevant to a given vfsmount locked.
  69  */
  70 static void fsnotify_recalc_vfsmount_mask_locked(struct vfsmount *mnt)
  71 {
  72         struct mount *m = real_mount(mnt);
  73         struct fsnotify_mark *mark;
  74         __u32 new_mask = 0;
  75
  76         assert_spin_locked(&mnt->mnt_root->d_lock);
  77
  78         hlist_for_each_entry(mark, &m->mnt_fsnotify_marks, m.m_list)
  79                 new_mask |= mark->mask;
  80         m->mnt_fsnotify_mask = new_mask;
  81 }
  82
  83 /*
  84  * Recalculate the mnt->mnt_fsnotify_mask, or the mask of all FS_* event types
  85  * any notifier is interested in hearing for this mount point
  86  */
  87 void fsnotify_recalc_vfsmount_mask(struct vfsmount *mnt)
  88 {
  89         spin_lock(&mnt->mnt_root->d_lock);
  90         fsnotify_recalc_vfsmount_mask_locked(mnt);
  91         spin_unlock(&mnt->mnt_root->d_lock);
  92 }
  93
  94 void fsnotify_destroy_vfsmount_mark(struct fsnotify_mark *mark)
  95 {
  96         struct vfsmount *mnt = mark->m.mnt;
  97
  98         BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
  99         assert_spin_locked(&mark->lock);
 100
 101         spin_lock(&mnt->mnt_root->d_lock);
 102
 103         hlist_del_init_rcu(&mark->m.m_list);
 104         mark->m.mnt = NULL;
 105
 106         fsnotify_recalc_vfsmount_mask_locked(mnt);
 107
 108         spin_unlock(&mnt->mnt_root->d_lock);
 109 }
 110
 111 static struct fsnotify_mark *fsnotify_find_vfsmount_mark_locked(struct fsnotify_group *group,
 112                                                                 struct vfsmount *mnt)
 113 {
 114         struct mount *m = real_mount(mnt);
 115         struct fsnotify_mark *mark;
 116
 117         assert_spin_locked(&mnt->mnt_root->d_lock);
 118
 119         hlist_for_each_entry(mark, &m->mnt_fsnotify_marks, m.m_list) {
 120                 if (mark->group == group) {
 121                         fsnotify_get_mark(mark);
 122                         return mark;
 123                 }
 124         }
 125         return NULL;
 126 }
 127
 128 /*
 129  * given a group and vfsmount, find the mark associated with that combination.
 130  * if found take a reference to that mark and return it, else return NULL
 131  */
 132 struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group,
 133                                                   struct vfsmount *mnt)
 134 {
 135         struct fsnotify_mark *mark;
 136
 137         spin_lock(&mnt->mnt_root->d_lock);
 138         mark = fsnotify_find_vfsmount_mark_locked(group, mnt);
 139         spin_unlock(&mnt->mnt_root->d_lock);
 140
 141         return mark;
 142 }
 143
 144 /*
 145  * Attach an initialized mark to a given group and vfsmount.
 146  * These marks may be used for the fsnotify backend to determine which
 147  * event types should be delivered to which groups.
 148  */
 149 int fsnotify_add_vfsmount_mark(struct fsnotify_mark *mark,
 150                                struct fsnotify_group *group, struct vfsmount *mnt,
 151                                int allow_dups)
 152 {
 153         struct mount *m = real_mount(mnt);
 154         struct fsnotify_mark *lmark, *last = NULL;
 155         int ret = 0;
 156
 157         mark->flags |= FSNOTIFY_MARK_FLAG_VFSMOUNT;
 158
 159         BUG_ON(!mutex_is_locked(&group->mark_mutex));
 160         assert_spin_locked(&mark->lock);
 161
 162         spin_lock(&mnt->mnt_root->d_lock);
 163
 164         mark->m.mnt = mnt;
 165
 166         /* is mark the first mark? */
 167         if (hlist_empty(&m->mnt_fsnotify_marks)) {
 168                 hlist_add_head_rcu(&mark->m.m_list, &m->mnt_fsnotify_marks);
 169                 goto out;
 170         }
 171
 172         /* should mark be in the middle of the current list? */
 173         hlist_for_each_entry(lmark, &m->mnt_fsnotify_marks, m.m_list) {
 174                 last = lmark;
 175
 176                 if ((lmark->group == group) && !allow_dups) {
 177                         ret = -EEXIST;
 178                         goto out;
 179                 }
 180
 181                 if (mark->group->priority < lmark->group->priority)
 182                         continue;
 183
 184                 if ((mark->group->priority == lmark->group->priority) &&
 185                     (mark->group < lmark->group))
 186                         continue;
 187
 188                 hlist_add_before_rcu(&mark->m.m_list, &lmark->m.m_list);
 189                 goto out;
 190         }
 191
 192         BUG_ON(last == NULL);
 193         /* mark should be the last entry.  last is the current last entry */
 194         hlist_add_after_rcu(&last->m.m_list, &mark->m.m_list);
 195 out:
 196         fsnotify_recalc_vfsmount_mask_locked(mnt);
 197         spin_unlock(&mnt->mnt_root->d_lock);
 198
 199         return ret;
 200 }