module/zfs/zfs_onexit.c

   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 https://opensource.org/licenses/CDDL-1.0.
  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
  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
  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_remove_head(&zo->zo_actions)) != NULL) {
  91                 mutex_exit(&zo->zo_lock);
  92                 ap->za_func(ap->za_data);
  93                 kmem_free(ap, sizeof (zfs_onexit_action_node_t));
  94                 mutex_enter(&zo->zo_lock);
  95         }
  96         mutex_exit(&zo->zo_lock);
  97
  98         list_destroy(&zo->zo_actions);
  99         mutex_destroy(&zo->zo_lock);
 100         kmem_free(zo, sizeof (zfs_onexit_t));
 101 }
 102
 103 /*
 104  * Consumers might need to operate by minor number instead of fd, since
 105  * they might be running in another thread (e.g. txg_sync_thread). Callers
 106  * of this function must call zfs_onexit_fd_rele() when they're finished
 107  * using the minor number.
 108  */
 109 zfs_file_t *
 110 zfs_onexit_fd_hold(int fd, minor_t *minorp)
 111 {
 112         zfs_onexit_t *zo = NULL;
 113
 114         zfs_file_t *fp = zfs_file_get(fd);
 115         if (fp == NULL)
 116                 return (NULL);
 117
 118         int error = zfsdev_getminor(fp, minorp);
 119         if (error) {
 120                 zfs_onexit_fd_rele(fp);
 121                 return (NULL);
 122         }
 123
 124         zo = zfsdev_get_state(*minorp, ZST_ONEXIT);
 125         if (zo == NULL) {
 126                 zfs_onexit_fd_rele(fp);
 127                 return (NULL);
 128         }
 129         return (fp);
 130 }
 131
 132 void
 133 zfs_onexit_fd_rele(zfs_file_t *fp)
 134 {
 135         zfs_file_put(fp);
 136 }
 137
 138 static int
 139 zfs_onexit_minor_to_state(minor_t minor, zfs_onexit_t **zo)
 140 {
 141         *zo = zfsdev_get_state(minor, ZST_ONEXIT);
 142         if (*zo == NULL)
 143                 return (SET_ERROR(EBADF));
 144
 145         return (0);
 146 }
 147
 148 /*
 149  * Add a callback to be invoked when the calling process exits.
 150  */
 151 int
 152 zfs_onexit_add_cb(minor_t minor, void (*func)(void *), void *data,
 153     uintptr_t *action_handle)
 154 {
 155         zfs_onexit_t *zo;
 156         zfs_onexit_action_node_t *ap;
 157         int error;
 158
 159         error = zfs_onexit_minor_to_state(minor, &zo);
 160         if (error)
 161                 return (error);
 162
 163         ap = kmem_alloc(sizeof (zfs_onexit_action_node_t), KM_SLEEP);
 164         list_link_init(&ap->za_link);
 165         ap->za_func = func;
 166         ap->za_data = data;
 167
 168         mutex_enter(&zo->zo_lock);
 169         list_insert_tail(&zo->zo_actions, ap);
 170         mutex_exit(&zo->zo_lock);
 171         if (action_handle)
 172                 *action_handle = (uintptr_t)ap;
 173
 174         return (0);
 175 }