| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame] | 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/list.h> |
| 20 | #include <linux/mutex.h> |
| 21 | #include <linux/slab.h> |
| 22 | #include <linux/srcu.h> |
| 23 | #include <linux/rculist.h> |
| 24 | #include <linux/wait.h> |
| 25 | |
| 26 | #include <linux/fsnotify_backend.h> |
| 27 | #include "fsnotify.h" |
| 28 | |
| 29 | #include <linux/atomic.h> |
| 30 | |
| 31 | /* |
| 32 | * Final freeing of a group |
| 33 | */ |
| 34 | void fsnotify_final_destroy_group(struct fsnotify_group *group) |
| 35 | { |
| 36 | /* clear the notification queue of all events */ |
| 37 | fsnotify_flush_notify(group); |
| 38 | |
| 39 | if (group->ops->free_group_priv) |
| 40 | group->ops->free_group_priv(group); |
| 41 | |
| 42 | kfree(group); |
| 43 | } |
| 44 | |
| 45 | /* |
| 46 | * Trying to get rid of a group. We need to first get rid of any outstanding |
| 47 | * allocations and then free the group. Remember that fsnotify_clear_marks_by_group |
| 48 | * could miss marks that are being freed by inode and those marks could still |
| 49 | * hold a reference to this group (via group->num_marks) If we get into that |
| 50 | * situtation, the fsnotify_final_destroy_group will get called when that final |
| 51 | * mark is freed. |
| 52 | */ |
| 53 | static void fsnotify_destroy_group(struct fsnotify_group *group) |
| 54 | { |
| 55 | /* clear all inode marks for this group */ |
| 56 | fsnotify_clear_marks_by_group(group); |
| 57 | |
| 58 | synchronize_srcu(&fsnotify_mark_srcu); |
| 59 | |
| 60 | /* past the point of no return, matches the initial value of 1 */ |
| 61 | if (atomic_dec_and_test(&group->num_marks)) |
| 62 | fsnotify_final_destroy_group(group); |
| 63 | } |
| 64 | |
| 65 | /* |
| 66 | * Drop a reference to a group. Free it if it's through. |
| 67 | */ |
| 68 | void fsnotify_put_group(struct fsnotify_group *group) |
| 69 | { |
| 70 | if (atomic_dec_and_test(&group->refcnt)) |
| 71 | fsnotify_destroy_group(group); |
| 72 | } |
| 73 | |
| 74 | /* |
| 75 | * Create a new fsnotify_group and hold a reference for the group returned. |
| 76 | */ |
| 77 | struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops) |
| 78 | { |
| 79 | struct fsnotify_group *group; |
| 80 | |
| 81 | group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL); |
| 82 | if (!group) |
| 83 | return ERR_PTR(-ENOMEM); |
| 84 | |
| 85 | /* set to 0 when there a no external references to this group */ |
| 86 | atomic_set(&group->refcnt, 1); |
| 87 | /* |
| 88 | * hits 0 when there are no external references AND no marks for |
| 89 | * this group |
| 90 | */ |
| 91 | atomic_set(&group->num_marks, 1); |
| 92 | |
| 93 | mutex_init(&group->notification_mutex); |
| 94 | INIT_LIST_HEAD(&group->notification_list); |
| 95 | init_waitqueue_head(&group->notification_waitq); |
| 96 | group->max_events = UINT_MAX; |
| 97 | |
| 98 | spin_lock_init(&group->mark_lock); |
| 99 | INIT_LIST_HEAD(&group->marks_list); |
| 100 | |
| 101 | group->ops = ops; |
| 102 | |
| 103 | return group; |
| 104 | } |