/* * Copyright (C) 2008 Red Hat, Inc., Eric Paris * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2, or (at your option) * any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; see the file COPYING. If not, write to * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */ #include #include #include #include #include #include #include #include "fsnotify.h" #include /* protects writes to fsnotify_groups and fsnotify_mask */ static DEFINE_MUTEX(fsnotify_grp_mutex); /* all groups registered to receive inode filesystem notifications */ LIST_HEAD(fsnotify_inode_groups); /* all groups registered to receive mount point filesystem notifications */ LIST_HEAD(fsnotify_vfsmount_groups); /* * Update the group->mask by running all of the marks associated with this * group and finding the bitwise | of all of the mark->mask. */ void fsnotify_recalc_group_mask(struct fsnotify_group *group) { __u32 mask = 0; struct fsnotify_mark *mark; spin_lock(&group->mark_lock); list_for_each_entry(mark, &group->marks_list, g_list) mask |= mark->mask; group->mask = mask; spin_unlock(&group->mark_lock); } void fsnotify_add_vfsmount_group(struct fsnotify_group *group) { struct fsnotify_group *group_iter; mutex_lock(&fsnotify_grp_mutex); if (!group->on_vfsmount_group_list) { list_for_each_entry(group_iter, &fsnotify_vfsmount_groups, vfsmount_group_list) { /* insert in front of this one? */ if (group < group_iter) { /* list_add_tail() insert in front of group_iter */ list_add_tail_rcu(&group->inode_group_list, &group_iter->inode_group_list); goto out; } } /* apparently we need to be the last entry */ list_add_tail_rcu(&group->vfsmount_group_list, &fsnotify_vfsmount_groups); } out: group->on_vfsmount_group_list = 1; mutex_unlock(&fsnotify_grp_mutex); } void fsnotify_add_inode_group(struct fsnotify_group *group) { struct fsnotify_group *group_iter; mutex_lock(&fsnotify_grp_mutex); /* add to global group list */ if (!group->on_inode_group_list) { list_for_each_entry(group_iter, &fsnotify_inode_groups, inode_group_list) { if (group < group_iter) { /* list_add_tail() insert in front of group_iter */ list_add_tail_rcu(&group->inode_group_list, &group_iter->inode_group_list); goto out; } } /* apparently we need to be the last entry */ list_add_tail_rcu(&group->inode_group_list, &fsnotify_inode_groups); } out: group->on_inode_group_list = 1; mutex_unlock(&fsnotify_grp_mutex); } /* * Final freeing of a group */ void fsnotify_final_destroy_group(struct fsnotify_group *group) { /* clear the notification queue of all events */ fsnotify_flush_notify(group); if (group->ops->free_group_priv) group->ops->free_group_priv(group); kfree(group); } /* * Trying to get rid of a group. We need to first get rid of any outstanding * allocations and then free the group. Remember that fsnotify_clear_marks_by_group * could miss marks that are being freed by inode and those marks could still * hold a reference to this group (via group->num_marks) If we get into that * situtation, the fsnotify_final_destroy_group will get called when that final * mark is freed. */ static void fsnotify_destroy_group(struct fsnotify_group *group) { /* clear all inode marks for this group */ fsnotify_clear_marks_by_group(group); synchronize_srcu(&fsnotify_mark_srcu); /* past the point of no return, matches the initial value of 1 */ if (atomic_dec_and_test(&group->num_marks)) fsnotify_final_destroy_group(group); } /* * Remove this group from the global list of groups that will get events * this can be done even if there are still references and things still using * this group. This just stops the group from getting new events. */ static void __fsnotify_evict_group(struct fsnotify_group *group) { BUG_ON(!mutex_is_locked(&fsnotify_grp_mutex)); if (group->on_inode_group_list) list_del_rcu(&group->inode_group_list); group->on_inode_group_list = 0; if (group->on_vfsmount_group_list) list_del_rcu(&group->vfsmount_group_list); group->on_vfsmount_group_list = 0; } /* * Called when a group is no longer interested in getting events. This can be * used if a group is misbehaving or if for some reason a group should no longer * get any filesystem events. */ void fsnotify_evict_group(struct fsnotify_group *group) { mutex_lock(&fsnotify_grp_mutex); __fsnotify_evict_group(group); mutex_unlock(&fsnotify_grp_mutex); } /* * Drop a reference to a group. Free it if it's through. */ void fsnotify_put_group(struct fsnotify_group *group) { if (!atomic_dec_and_mutex_lock(&group->refcnt, &fsnotify_grp_mutex)) return; /* * OK, now we know that there's no other users *and* we hold mutex, * so no new references will appear */ __fsnotify_evict_group(group); mutex_unlock(&fsnotify_grp_mutex); fsnotify_destroy_group(group); } /* * Create a new fsnotify_group and hold a reference for the group returned. */ struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) { struct fsnotify_group *group; group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL); if (!group) return ERR_PTR(-ENOMEM); /* set to 0 when there a no external references to this group */ atomic_set(&group->refcnt, 1); /* * hits 0 when there are no external references AND no marks for * this group */ atomic_set(&group->num_marks, 1); mutex_init(&group->notification_mutex); INIT_LIST_HEAD(&group->notification_list); init_waitqueue_head(&group->notification_waitq); group->max_events = UINT_MAX; INIT_LIST_HEAD(&group->inode_group_list); INIT_LIST_HEAD(&group->vfsmount_group_list); spin_lock_init(&group->mark_lock); INIT_LIST_HEAD(&group->marks_list); group->ops = ops; return group; }