1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright (c) 2013, 2020 by Delphix. All rights reserved.
24 */
25
26 #include <sys/types.h>
27 #include <sys/param.h>
28 #include <sys/errno.h>
29 #include <sys/kmem.h>
30 #include <sys/sunddi.h>
31 #include <sys/zfs_ioctl.h>
32 #include <sys/zfs_onexit.h>
33 #include <sys/zvol.h>
34
35 /*
36 * ZFS kernel routines may add/delete callback routines to be invoked
37 * upon process exit (triggered via the close operation from the /dev/zfs
38 * driver).
39 *
40 * These cleanup callbacks are intended to allow for the accumulation
41 * of kernel state across multiple ioctls. User processes participate
42 * simply by opening ZFS_DEV. This causes the ZFS driver to do create
43 * some private data for the file descriptor and generating a unique
44 * minor number. The process then passes along that file descriptor to
45 * each ioctl that might have a cleanup operation.
46 *
47 * Consumers of the onexit routines should call zfs_onexit_fd_hold() early
48 * on to validate the given fd and add a reference to its file table entry.
49 * This allows the consumer to do its work and then add a callback, knowing
50 * that zfs_onexit_add_cb() won't fail with EBADF. When finished, consumers
51 * should call zfs_onexit_fd_rele().
52 *
53 * A simple example is zfs_ioc_recv(), where we might create an AVL tree
54 * with dataset/GUID mappings and then reuse that tree on subsequent
55 * zfs_ioc_recv() calls.
56 *
57 * On the first zfs_ioc_recv() call, dmu_recv_stream() will kmem_alloc()
58 * the AVL tree and pass it along with a callback function to
59 * zfs_onexit_add_cb(). The zfs_onexit_add_cb() routine will register the
60 * callback and return an action handle.
61 *
62 * The action handle is then passed from user space to subsequent
63 * zfs_ioc_recv() calls, so that dmu_recv_stream() can fetch its AVL tree
64 * by calling zfs_onexit_cb_data() with the device minor number and
65 * action handle.
66 *
67 * If the user process exits abnormally, the callback is invoked implicitly
68 * as part of the driver close operation. Once the user space process is
69 * finished with the accumulated kernel state, it can also just call close(2)
70 * on the cleanup fd to trigger the cleanup callback.
71 */
72
73 void
zfs_onexit_init(zfs_onexit_t ** zop)74 zfs_onexit_init(zfs_onexit_t **zop)
75 {
76 zfs_onexit_t *zo;
77
78 zo = *zop = kmem_zalloc(sizeof (zfs_onexit_t), KM_SLEEP);
79 mutex_init(&zo->zo_lock, NULL, MUTEX_DEFAULT, NULL);
80 list_create(&zo->zo_actions, sizeof (zfs_onexit_action_node_t),
81 offsetof(zfs_onexit_action_node_t, za_link));
82 }
83
84 void
zfs_onexit_destroy(zfs_onexit_t * zo)85 zfs_onexit_destroy(zfs_onexit_t *zo)
86 {
87 zfs_onexit_action_node_t *ap;
88
89 mutex_enter(&zo->zo_lock);
90 while ((ap = list_head(&zo->zo_actions)) != NULL) {
91 list_remove(&zo->zo_actions, ap);
92 mutex_exit(&zo->zo_lock);
93 ap->za_func(ap->za_data);
94 kmem_free(ap, sizeof (zfs_onexit_action_node_t));
95 mutex_enter(&zo->zo_lock);
96 }
97 mutex_exit(&zo->zo_lock);
98
99 list_destroy(&zo->zo_actions);
100 mutex_destroy(&zo->zo_lock);
101 kmem_free(zo, sizeof (zfs_onexit_t));
102 }
103
104 /*
105 * Consumers might need to operate by minor number instead of fd, since
106 * they might be running in another thread (e.g. txg_sync_thread). Callers
107 * of this function must call zfs_onexit_fd_rele() when they're finished
108 * using the minor number.
109 */
110 int
zfs_onexit_fd_hold(int fd,minor_t * minorp)111 zfs_onexit_fd_hold(int fd, minor_t *minorp)
112 {
113 zfs_onexit_t *zo = NULL;
114 int error;
115
116 error = zfsdev_getminor(fd, minorp);
117 if (error) {
118 zfs_onexit_fd_rele(fd);
119 return (error);
120 }
121
122 zo = zfsdev_get_state(*minorp, ZST_ONEXIT);
123 if (zo == NULL) {
124 zfs_onexit_fd_rele(fd);
125 return (SET_ERROR(EBADF));
126 }
127 return (0);
128 }
129
130 void
zfs_onexit_fd_rele(int fd)131 zfs_onexit_fd_rele(int fd)
132 {
133 zfs_file_put(fd);
134 }
135
136 static int
zfs_onexit_minor_to_state(minor_t minor,zfs_onexit_t ** zo)137 zfs_onexit_minor_to_state(minor_t minor, zfs_onexit_t **zo)
138 {
139 *zo = zfsdev_get_state(minor, ZST_ONEXIT);
140 if (*zo == NULL)
141 return (SET_ERROR(EBADF));
142
143 return (0);
144 }
145
146 /*
147 * Add a callback to be invoked when the calling process exits.
148 */
149 int
zfs_onexit_add_cb(minor_t minor,void (* func)(void *),void * data,uint64_t * action_handle)150 zfs_onexit_add_cb(minor_t minor, void (*func)(void *), void *data,
151 uint64_t *action_handle)
152 {
153 zfs_onexit_t *zo;
154 zfs_onexit_action_node_t *ap;
155 int error;
156
157 error = zfs_onexit_minor_to_state(minor, &zo);
158 if (error)
159 return (error);
160
161 ap = kmem_alloc(sizeof (zfs_onexit_action_node_t), KM_SLEEP);
162 list_link_init(&ap->za_link);
163 ap->za_func = func;
164 ap->za_data = data;
165
166 mutex_enter(&zo->zo_lock);
167 list_insert_tail(&zo->zo_actions, ap);
168 mutex_exit(&zo->zo_lock);
169 if (action_handle)
170 *action_handle = (uint64_t)(uintptr_t)ap;
171
172 return (0);
173 }
174