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