kernel/fs/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 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 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/open.h>
  30 #include <sys/kmem.h>
  31 #include <sys/conf.h>
  32 #include <sys/ddi.h>
  33 #include <sys/sunddi.h>
  34 #include <sys/zfs_ioctl.h>
  35 #include <sys/mkdev.h>
  36 #include <sys/zfs_onexit.h>
  37 #include <sys/zvol.h>
  38
  39 /*
  40  * ZFS kernel routines may add/delete callback routines to be invoked
  41  * upon process exit (triggered via the close operation from the /dev/zfs
  42  * driver).
  43  *
  44  * These cleanup callbacks are intended to allow for the accumulation
  45  * of kernel state across multiple ioctls.  User processes participate
  46  * by opening ZFS_DEV with O_EXCL. This causes the ZFS driver to do a
  47  * clone-open, generating a unique minor number. The process then passes
  48  * along that file descriptor to each ioctl that might have a cleanup operation.
  49  *
  50  * Consumers of the onexit routines should call zfs_onexit_fd_hold() early
  51  * on to validate the given fd and add a reference to its file table entry.
  52  * This allows the consumer to do its work and then add a callback, knowing
  53  * that zfs_onexit_add_cb() won't fail with EBADF.  When finished, consumers
  54  * should call zfs_onexit_fd_rele().
  55  *
  56  * A simple example is zfs_ioc_recv(), where we might create an AVL tree
  57  * with dataset/GUID mappings and then reuse that tree on subsequent
  58  * zfs_ioc_recv() calls.
  59  *
  60  * On the first zfs_ioc_recv() call, dmu_recv_stream() will kmem_alloc()
  61  * the AVL tree and pass it along with a callback function to
  62  * zfs_onexit_add_cb(). The zfs_onexit_add_cb() routine will register the
  63  * callback and return an action handle.
  64  *
  65  * The action handle is then passed from user space to subsequent
  66  * zfs_ioc_recv() calls, so that dmu_recv_stream() can fetch its AVL tree
  67  * by calling zfs_onexit_cb_data() with the device minor number and
  68  * action handle.
  69  *
  70  * If the user process exits abnormally, the callback is invoked implicitly
  71  * as part of the driver close operation.  Once the user space process is
  72  * finished with the accumulated kernel state, it can also just call close(2)
  73  * on the cleanup fd to trigger the cleanup callback.
  74  */
  75
  76 void
  77 zfs_onexit_init(zfs_onexit_t **zop)
  78 {
  79         zfs_onexit_t *zo;
  80
  81         zo = *zop = kmem_zalloc(sizeof (zfs_onexit_t), KM_SLEEP);
  82         mutex_init(&zo->zo_lock, NULL, MUTEX_DEFAULT, NULL);
  83         list_create(&zo->zo_actions, sizeof (zfs_onexit_action_node_t),
  84             offsetof(zfs_onexit_action_node_t, za_link));
  85 }
  86
  87 void
  88 zfs_onexit_destroy(zfs_onexit_t *zo)
  89 {
  90         zfs_onexit_action_node_t *ap;
  91
  92         mutex_enter(&zo->zo_lock);
  93         while ((ap = list_head(&zo->zo_actions)) != NULL) {
  94                 list_remove(&zo->zo_actions, ap);
  95                 mutex_exit(&zo->zo_lock);
  96                 ap->za_func(ap->za_data);
  97                 kmem_free(ap, sizeof (zfs_onexit_action_node_t));
  98                 mutex_enter(&zo->zo_lock);
  99         }
 100         mutex_exit(&zo->zo_lock);
 101
 102         list_destroy(&zo->zo_actions);
 103         mutex_destroy(&zo->zo_lock);
 104         kmem_free(zo, sizeof (zfs_onexit_t));
 105 }
 106
 107 static int
 108 zfs_onexit_minor_to_state(minor_t minor, zfs_onexit_t **zo)
 109 {
 110         *zo = zfsdev_get_soft_state(minor, ZSST_CTLDEV);
 111         if (*zo == NULL)
 112                 return (SET_ERROR(EBADF));
 113
 114         return (0);
 115 }
 116
 117 /*
 118  * Consumers might need to operate by minor number instead of fd, since
 119  * they might be running in another thread (e.g. txg_sync_thread). Callers
 120  * of this function must call zfs_onexit_fd_rele() when they're finished
 121  * using the minor number.
 122  */
 123 int
 124 zfs_onexit_fd_hold(int fd, minor_t *minorp)
 125 {
 126         file_t *fp;
 127         zfs_onexit_t *zo;
 128
 129         fp = getf(fd);
 130         if (fp == NULL)
 131                 return (SET_ERROR(EBADF));
 132
 133         *minorp = getminor(fp->f_vnode->v_rdev);
 134         return (zfs_onexit_minor_to_state(*minorp, &zo));
 135 }
 136
 137 void
 138 zfs_onexit_fd_rele(int fd)
 139 {
 140         releasef(fd);
 141 }
 142
 143 /*
 144  * Add a callback to be invoked when the calling process exits.
 145  */
 146 int
 147 zfs_onexit_add_cb(minor_t minor, void (*func)(void *), void *data,
 148     uint64_t *action_handle)
 149 {
 150         zfs_onexit_t *zo;
 151         zfs_onexit_action_node_t *ap;
 152         int error;
 153
 154         error = zfs_onexit_minor_to_state(minor, &zo);
 155         if (error)
 156                 return (error);
 157
 158         ap = kmem_alloc(sizeof (zfs_onexit_action_node_t), KM_SLEEP);
 159         list_link_init(&ap->za_link);
 160         ap->za_func = func;
 161         ap->za_data = data;
 162
 163         mutex_enter(&zo->zo_lock);
 164         list_insert_tail(&zo->zo_actions, ap);
 165         mutex_exit(&zo->zo_lock);
 166         if (action_handle)
 167                 *action_handle = (uint64_t)(uintptr_t)ap;
 168
 169         return (0);
 170 }
 171
 172 static zfs_onexit_action_node_t *
 173 zfs_onexit_find_cb(zfs_onexit_t *zo, uint64_t action_handle)
 174 {
 175         zfs_onexit_action_node_t *match;
 176         zfs_onexit_action_node_t *ap;
 177         list_t *l;
 178
 179         ASSERT(MUTEX_HELD(&zo->zo_lock));
 180
 181         match = (zfs_onexit_action_node_t *)(uintptr_t)action_handle;
 182         l = &zo->zo_actions;
 183         for (ap = list_head(l); ap != NULL; ap = list_next(l, ap)) {
 184                 if (match == ap)
 185                         break;
 186         }
 187         return (ap);
 188 }
 189
 190 /*
 191  * Delete the callback, triggering it first if 'fire' is set.
 192  */
 193 int
 194 zfs_onexit_del_cb(minor_t minor, uint64_t action_handle, boolean_t fire)
 195 {
 196         zfs_onexit_t *zo;
 197         zfs_onexit_action_node_t *ap;
 198         int error;
 199
 200         error = zfs_onexit_minor_to_state(minor, &zo);
 201         if (error)
 202                 return (error);
 203
 204         mutex_enter(&zo->zo_lock);
 205         ap = zfs_onexit_find_cb(zo, action_handle);
 206         if (ap != NULL) {
 207                 list_remove(&zo->zo_actions, ap);
 208                 mutex_exit(&zo->zo_lock);
 209                 if (fire)
 210                         ap->za_func(ap->za_data);
 211                 kmem_free(ap, sizeof (zfs_onexit_action_node_t));
 212         } else {
 213                 mutex_exit(&zo->zo_lock);
 214                 error = SET_ERROR(ENOENT);
 215         }
 216
 217         return (error);
 218 }
 219
 220 /*
 221  * Return the data associated with this callback.  This allows consumers
 222  * of the cleanup-on-exit interfaces to stash kernel data across system
 223  * calls, knowing that it will be cleaned up if the calling process exits.
 224  */
 225 int
 226 zfs_onexit_cb_data(minor_t minor, uint64_t action_handle, void **data)
 227 {
 228         zfs_onexit_t *zo;
 229         zfs_onexit_action_node_t *ap;
 230         int error;
 231
 232         *data = NULL;
 233
 234         error = zfs_onexit_minor_to_state(minor, &zo);
 235         if (error)
 236                 return (error);
 237
 238         mutex_enter(&zo->zo_lock);
 239         ap = zfs_onexit_find_cb(zo, action_handle);
 240         if (ap != NULL)
 241                 *data = ap->za_data;
 242         else
 243                 error = SET_ERROR(ENOENT);
 244         mutex_exit(&zo->zo_lock);
 245
 246         return (error);
 247 }