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) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23  * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
24  * Copyright (c) 2017, Intel Corporation.
25  */
26 
27 #ifndef _SYS_VDEV_IMPL_H
28 #define	_SYS_VDEV_IMPL_H
29 
30 #include <sys/avl.h>
31 #include <sys/bpobj.h>
32 #include <sys/dmu.h>
33 #include <sys/metaslab.h>
34 #include <sys/nvpair.h>
35 #include <sys/space_map.h>
36 #include <sys/vdev.h>
37 #include <sys/dkio.h>
38 #include <sys/uberblock_impl.h>
39 #include <sys/vdev_indirect_mapping.h>
40 #include <sys/vdev_indirect_births.h>
41 #include <sys/vdev_removal.h>
42 
43 #ifdef	__cplusplus
44 extern "C" {
45 #endif
46 
47 /*
48  * Virtual device descriptors.
49  *
50  * All storage pool operations go through the virtual device framework,
51  * which provides data replication and I/O scheduling.
52  */
53 
54 /*
55  * Forward declarations that lots of things need.
56  */
57 typedef struct vdev_queue vdev_queue_t;
58 typedef struct vdev_cache vdev_cache_t;
59 typedef struct vdev_cache_entry vdev_cache_entry_t;
60 struct abd;
61 
62 extern int zfs_vdev_queue_depth_pct;
63 extern int zfs_vdev_def_queue_depth;
64 extern uint32_t zfs_vdev_async_write_max_active;
65 
66 /*
67  * Virtual device operations
68  */
69 typedef int	vdev_open_func_t(vdev_t *vd, uint64_t *size, uint64_t *max_size,
70     uint64_t *ashift);
71 typedef void	vdev_close_func_t(vdev_t *vd);
72 typedef uint64_t vdev_asize_func_t(vdev_t *vd, uint64_t psize);
73 typedef void	vdev_io_start_func_t(zio_t *zio);
74 typedef void	vdev_io_done_func_t(zio_t *zio);
75 typedef void	vdev_state_change_func_t(vdev_t *vd, int, int);
76 typedef void	vdev_hold_func_t(vdev_t *vd);
77 typedef void	vdev_rele_func_t(vdev_t *vd);
78 
79 typedef void	vdev_remap_cb_t(uint64_t inner_offset, vdev_t *vd,
80     uint64_t offset, uint64_t size, void *arg);
81 typedef void	vdev_remap_func_t(vdev_t *vd, uint64_t offset, uint64_t size,
82     vdev_remap_cb_t callback, void *arg);
83 /*
84  * Given a target vdev, translates the logical range "in" to the physical
85  * range "res"
86  */
87 typedef void vdev_xlation_func_t(vdev_t *cvd, const range_seg_t *in,
88     range_seg_t *res);
89 
90 typedef struct vdev_ops {
91 	vdev_open_func_t		*vdev_op_open;
92 	vdev_close_func_t		*vdev_op_close;
93 	vdev_asize_func_t		*vdev_op_asize;
94 	vdev_io_start_func_t		*vdev_op_io_start;
95 	vdev_io_done_func_t		*vdev_op_io_done;
96 	vdev_state_change_func_t	*vdev_op_state_change;
97 	vdev_hold_func_t		*vdev_op_hold;
98 	vdev_rele_func_t		*vdev_op_rele;
99 	vdev_remap_func_t		*vdev_op_remap;
100 	/*
101 	 * For translating ranges from non-leaf vdevs (e.g. raidz) to leaves.
102 	 * Used when initializing vdevs. Isn't used by leaf ops.
103 	 */
104 	vdev_xlation_func_t		*vdev_op_xlate;
105 	char				vdev_op_type[16];
106 	boolean_t			vdev_op_leaf;
107 } vdev_ops_t;
108 
109 /*
110  * Virtual device properties
111  */
112 struct vdev_cache_entry {
113 	struct abd	*ve_abd;
114 	uint64_t	ve_offset;
115 	uint64_t	ve_lastused;
116 	avl_node_t	ve_offset_node;
117 	avl_node_t	ve_lastused_node;
118 	uint32_t	ve_hits;
119 	uint16_t	ve_missed_update;
120 	zio_t		*ve_fill_io;
121 };
122 
123 struct vdev_cache {
124 	avl_tree_t	vc_offset_tree;
125 	avl_tree_t	vc_lastused_tree;
126 	kmutex_t	vc_lock;
127 };
128 
129 typedef struct vdev_queue_class {
130 	uint32_t	vqc_active;
131 
132 	/*
133 	 * Sorted by offset or timestamp, depending on if the queue is
134 	 * LBA-ordered vs FIFO.
135 	 */
136 	avl_tree_t	vqc_queued_tree;
137 } vdev_queue_class_t;
138 
139 struct vdev_queue {
140 	vdev_t		*vq_vdev;
141 	vdev_queue_class_t vq_class[ZIO_PRIORITY_NUM_QUEUEABLE];
142 	avl_tree_t	vq_active_tree;
143 	avl_tree_t	vq_read_offset_tree;
144 	avl_tree_t	vq_write_offset_tree;
145 	uint64_t	vq_last_offset;
146 	hrtime_t	vq_io_complete_ts; /* time last i/o completed */
147 	kmutex_t	vq_lock;
148 };
149 
150 typedef enum vdev_alloc_bias {
151 	VDEV_BIAS_NONE,
152 	VDEV_BIAS_LOG,		/* dedicated to ZIL data (SLOG) */
153 	VDEV_BIAS_SPECIAL,	/* dedicated to ddt, metadata, and small blks */
154 	VDEV_BIAS_DEDUP		/* dedicated to dedup metadata */
155 } vdev_alloc_bias_t;
156 
157 
158 /*
159  * On-disk indirect vdev state.
160  *
161  * An indirect vdev is described exclusively in the MOS config of a pool.
162  * The config for an indirect vdev includes several fields, which are
163  * accessed in memory by a vdev_indirect_config_t.
164  */
165 typedef struct vdev_indirect_config {
166 	/*
167 	 * Object (in MOS) which contains the indirect mapping. This object
168 	 * contains an array of vdev_indirect_mapping_entry_phys_t ordered by
169 	 * vimep_src. The bonus buffer for this object is a
170 	 * vdev_indirect_mapping_phys_t. This object is allocated when a vdev
171 	 * removal is initiated.
172 	 *
173 	 * Note that this object can be empty if none of the data on the vdev
174 	 * has been copied yet.
175 	 */
176 	uint64_t	vic_mapping_object;
177 
178 	/*
179 	 * Object (in MOS) which contains the birth times for the mapping
180 	 * entries. This object contains an array of
181 	 * vdev_indirect_birth_entry_phys_t sorted by vibe_offset. The bonus
182 	 * buffer for this object is a vdev_indirect_birth_phys_t. This object
183 	 * is allocated when a vdev removal is initiated.
184 	 *
185 	 * Note that this object can be empty if none of the vdev has yet been
186 	 * copied.
187 	 */
188 	uint64_t	vic_births_object;
189 
190 	/*
191 	 * This is the vdev ID which was removed previous to this vdev, or
192 	 * UINT64_MAX if there are no previously removed vdevs.
193 	 */
194 	uint64_t	vic_prev_indirect_vdev;
195 } vdev_indirect_config_t;
196 
197 /*
198  * Virtual device descriptor
199  */
200 struct vdev {
201 	/*
202 	 * Common to all vdev types.
203 	 */
204 	uint64_t	vdev_id;	/* child number in vdev parent	*/
205 	uint64_t	vdev_guid;	/* unique ID for this vdev	*/
206 	uint64_t	vdev_guid_sum;	/* self guid + all child guids	*/
207 	uint64_t	vdev_orig_guid;	/* orig. guid prior to remove	*/
208 	uint64_t	vdev_asize;	/* allocatable device capacity	*/
209 	uint64_t	vdev_min_asize;	/* min acceptable asize		*/
210 	uint64_t	vdev_max_asize;	/* max acceptable asize		*/
211 	uint64_t	vdev_ashift;	/* block alignment shift	*/
212 	uint64_t	vdev_state;	/* see VDEV_STATE_* #defines	*/
213 	uint64_t	vdev_prevstate;	/* used when reopening a vdev	*/
214 	vdev_ops_t	*vdev_ops;	/* vdev operations		*/
215 	spa_t		*vdev_spa;	/* spa for this vdev		*/
216 	void		*vdev_tsd;	/* type-specific data		*/
217 	vnode_t		*vdev_name_vp;	/* vnode for pathname		*/
218 	vnode_t		*vdev_devid_vp;	/* vnode for devid		*/
219 	vdev_t		*vdev_top;	/* top-level vdev		*/
220 	vdev_t		*vdev_parent;	/* parent vdev			*/
221 	vdev_t		**vdev_child;	/* array of children		*/
222 	uint64_t	vdev_children;	/* number of children		*/
223 	vdev_stat_t	vdev_stat;	/* virtual device statistics	*/
224 	boolean_t	vdev_expanding;	/* expand the vdev?		*/
225 	boolean_t	vdev_reopening;	/* reopen in progress?		*/
226 	int		vdev_open_error; /* error on last open		*/
227 	kthread_t	*vdev_open_thread; /* thread opening children	*/
228 	uint64_t	vdev_crtxg;	/* txg when top-level was added */
229 
230 	/*
231 	 * Top-level vdev state.
232 	 */
233 	uint64_t	vdev_ms_array;	/* metaslab array object	*/
234 	uint64_t	vdev_ms_shift;	/* metaslab size shift		*/
235 	uint64_t	vdev_ms_count;	/* number of metaslabs		*/
236 	metaslab_group_t *vdev_mg;	/* metaslab group		*/
237 	metaslab_t	**vdev_ms;	/* metaslab array		*/
238 	txg_list_t	vdev_ms_list;	/* per-txg dirty metaslab lists	*/
239 	txg_list_t	vdev_dtl_list;	/* per-txg dirty DTL lists	*/
240 	txg_node_t	vdev_txg_node;	/* per-txg dirty vdev linkage	*/
241 	boolean_t	vdev_remove_wanted; /* async remove wanted?	*/
242 	boolean_t	vdev_probe_wanted; /* async probe wanted?	*/
243 	list_node_t	vdev_config_dirty_node; /* config dirty list	*/
244 	list_node_t	vdev_state_dirty_node; /* state dirty list	*/
245 	uint64_t	vdev_deflate_ratio; /* deflation ratio (x512)	*/
246 	uint64_t	vdev_islog;	/* is an intent log device	*/
247 	uint64_t	vdev_removing;	/* device is being removed?	*/
248 	boolean_t	vdev_ishole;	/* is a hole in the namespace	*/
249 	uint64_t	vdev_top_zap;
250 	vdev_alloc_bias_t vdev_alloc_bias; /* metaslab allocation bias	*/
251 
252 	/* pool checkpoint related */
253 	space_map_t	*vdev_checkpoint_sm;	/* contains reserved blocks */
254 
255 	boolean_t	vdev_initialize_exit_wanted;
256 	vdev_initializing_state_t	vdev_initialize_state;
257 	kthread_t	*vdev_initialize_thread;
258 	/* Protects vdev_initialize_thread and vdev_initialize_state. */
259 	kmutex_t	vdev_initialize_lock;
260 	kcondvar_t	vdev_initialize_cv;
261 	uint64_t	vdev_initialize_offset[TXG_SIZE];
262 	uint64_t	vdev_initialize_last_offset;
263 	range_tree_t	*vdev_initialize_tree;	/* valid while initializing */
264 	uint64_t	vdev_initialize_bytes_est;
265 	uint64_t	vdev_initialize_bytes_done;
266 	time_t		vdev_initialize_action_time;	/* start and end time */
267 
268 	/* for limiting outstanding I/Os */
269 	kmutex_t	vdev_initialize_io_lock;
270 	kcondvar_t	vdev_initialize_io_cv;
271 	uint64_t	vdev_initialize_inflight;
272 
273 	/*
274 	 * Values stored in the config for an indirect or removing vdev.
275 	 */
276 	vdev_indirect_config_t	vdev_indirect_config;
277 
278 	/*
279 	 * The vdev_indirect_rwlock protects the vdev_indirect_mapping
280 	 * pointer from changing on indirect vdevs (when it is condensed).
281 	 * Note that removing (not yet indirect) vdevs have different
282 	 * access patterns (the mapping is not accessed from open context,
283 	 * e.g. from zio_read) and locking strategy (e.g. svr_lock).
284 	 */
285 	krwlock_t vdev_indirect_rwlock;
286 	vdev_indirect_mapping_t *vdev_indirect_mapping;
287 	vdev_indirect_births_t *vdev_indirect_births;
288 
289 	/*
290 	 * In memory data structures used to manage the obsolete sm, for
291 	 * indirect or removing vdevs.
292 	 *
293 	 * The vdev_obsolete_segments is the in-core record of the segments
294 	 * that are no longer referenced anywhere in the pool (due to
295 	 * being freed or remapped and not referenced by any snapshots).
296 	 * During a sync, segments are added to vdev_obsolete_segments
297 	 * via vdev_indirect_mark_obsolete(); at the end of each sync
298 	 * pass, this is appended to vdev_obsolete_sm via
299 	 * vdev_indirect_sync_obsolete().  The vdev_obsolete_lock
300 	 * protects against concurrent modifications of vdev_obsolete_segments
301 	 * from multiple zio threads.
302 	 */
303 	kmutex_t	vdev_obsolete_lock;
304 	range_tree_t	*vdev_obsolete_segments;
305 	space_map_t	*vdev_obsolete_sm;
306 
307 	/*
308 	 * Leaf vdev state.
309 	 */
310 	range_tree_t	*vdev_dtl[DTL_TYPES]; /* dirty time logs	*/
311 	space_map_t	*vdev_dtl_sm;	/* dirty time log space map	*/
312 	txg_node_t	vdev_dtl_node;	/* per-txg dirty DTL linkage	*/
313 	uint64_t	vdev_dtl_object; /* DTL object			*/
314 	uint64_t	vdev_psize;	/* physical device capacity	*/
315 	uint64_t	vdev_wholedisk;	/* true if this is a whole disk */
316 	uint64_t	vdev_offline;	/* persistent offline state	*/
317 	uint64_t	vdev_faulted;	/* persistent faulted state	*/
318 	uint64_t	vdev_degraded;	/* persistent degraded state	*/
319 	uint64_t	vdev_removed;	/* persistent removed state	*/
320 	uint64_t	vdev_resilver_txg; /* persistent resilvering state */
321 	uint64_t	vdev_nparity;	/* number of parity devices for raidz */
322 	char		*vdev_path;	/* vdev path (if any)		*/
323 	char		*vdev_devid;	/* vdev devid (if any)		*/
324 	char		*vdev_physpath;	/* vdev device path (if any)	*/
325 	char		*vdev_fru;	/* physical FRU location	*/
326 	uint64_t	vdev_not_present; /* not present during import	*/
327 	uint64_t	vdev_unspare;	/* unspare when resilvering done */
328 	boolean_t	vdev_nowritecache; /* true if flushwritecache failed */
329 	boolean_t	vdev_checkremove; /* temporary online test	*/
330 	boolean_t	vdev_forcefault; /* force online fault		*/
331 	boolean_t	vdev_splitting;	/* split or repair in progress  */
332 	boolean_t	vdev_delayed_close; /* delayed device close?	*/
333 	boolean_t	vdev_tmpoffline; /* device taken offline temporarily? */
334 	boolean_t	vdev_detached;	/* device detached?		*/
335 	boolean_t	vdev_cant_read;	/* vdev is failing all reads	*/
336 	boolean_t	vdev_cant_write; /* vdev is failing all writes	*/
337 	boolean_t	vdev_isspare;	/* was a hot spare		*/
338 	boolean_t	vdev_isl2cache;	/* was a l2cache device		*/
339 	vdev_queue_t	vdev_queue;	/* I/O deadline schedule queue	*/
340 	vdev_cache_t	vdev_cache;	/* physical block cache		*/
341 	spa_aux_vdev_t	*vdev_aux;	/* for l2cache and spares vdevs	*/
342 	zio_t		*vdev_probe_zio; /* root of current probe	*/
343 	vdev_aux_t	vdev_label_aux;	/* on-disk aux state		*/
344 	uint64_t	vdev_leaf_zap;
345 	hrtime_t	vdev_mmp_pending; /* 0 if write finished	*/
346 	uint64_t	vdev_mmp_kstat_id;	/* to find kstat entry */
347 	list_node_t	vdev_leaf_node;		/* leaf vdev list */
348 
349 	/*
350 	 * For DTrace to work in userland (libzpool) context, these fields must
351 	 * remain at the end of the structure.  DTrace will use the kernel's
352 	 * CTF definition for 'struct vdev', and since the size of a kmutex_t is
353 	 * larger in userland, the offsets for the rest of the fields would be
354 	 * incorrect.
355 	 */
356 	kmutex_t	vdev_dtl_lock;	/* vdev_dtl_{map,resilver}	*/
357 	kmutex_t	vdev_stat_lock;	/* vdev_stat			*/
358 	kmutex_t	vdev_probe_lock; /* protects vdev_probe_zio	*/
359 };
360 
361 #define	VDEV_RAIDZ_MAXPARITY	3
362 
363 #define	VDEV_PAD_SIZE		(8 << 10)
364 /* 2 padding areas (vl_pad1 and vl_pad2) to skip */
365 #define	VDEV_SKIP_SIZE		VDEV_PAD_SIZE * 2
366 #define	VDEV_PHYS_SIZE		(112 << 10)
367 #define	VDEV_UBERBLOCK_RING	(128 << 10)
368 
369 /*
370  * MMP blocks occupy the last MMP_BLOCKS_PER_LABEL slots in the uberblock
371  * ring when MMP is enabled.
372  */
373 #define	MMP_BLOCKS_PER_LABEL	1
374 
375 /* The largest uberblock we support is 8k. */
376 #define	MAX_UBERBLOCK_SHIFT (13)
377 #define	VDEV_UBERBLOCK_SHIFT(vd)	\
378 	MIN(MAX((vd)->vdev_top->vdev_ashift, UBERBLOCK_SHIFT), \
379 	    MAX_UBERBLOCK_SHIFT)
380 #define	VDEV_UBERBLOCK_COUNT(vd)	\
381 	(VDEV_UBERBLOCK_RING >> VDEV_UBERBLOCK_SHIFT(vd))
382 #define	VDEV_UBERBLOCK_OFFSET(vd, n)	\
383 	offsetof(vdev_label_t, vl_uberblock[(n) << VDEV_UBERBLOCK_SHIFT(vd)])
384 #define	VDEV_UBERBLOCK_SIZE(vd)		(1ULL << VDEV_UBERBLOCK_SHIFT(vd))
385 
386 typedef struct vdev_phys {
387 	char		vp_nvlist[VDEV_PHYS_SIZE - sizeof (zio_eck_t)];
388 	zio_eck_t	vp_zbt;
389 } vdev_phys_t;
390 
391 typedef struct vdev_label {
392 	char		vl_pad1[VDEV_PAD_SIZE];			/*  8K */
393 	char		vl_pad2[VDEV_PAD_SIZE];			/*  8K */
394 	vdev_phys_t	vl_vdev_phys;				/* 112K	*/
395 	char		vl_uberblock[VDEV_UBERBLOCK_RING];	/* 128K	*/
396 } vdev_label_t;							/* 256K total */
397 
398 /*
399  * vdev_dirty() flags
400  */
401 #define	VDD_METASLAB	0x01
402 #define	VDD_DTL		0x02
403 
404 /* Offset of embedded boot loader region on each label */
405 #define	VDEV_BOOT_OFFSET	(2 * sizeof (vdev_label_t))
406 /*
407  * Size of embedded boot loader region on each label.
408  * The total size of the first two labels plus the boot area is 4MB.
409  */
410 #define	VDEV_BOOT_SIZE		(7ULL << 19)			/* 3.5M */
411 
412 /*
413  * Size of label regions at the start and end of each leaf device.
414  */
415 #define	VDEV_LABEL_START_SIZE	(2 * sizeof (vdev_label_t) + VDEV_BOOT_SIZE)
416 #define	VDEV_LABEL_END_SIZE	(2 * sizeof (vdev_label_t))
417 #define	VDEV_LABELS		4
418 #define	VDEV_BEST_LABEL		VDEV_LABELS
419 
420 #define	VDEV_ALLOC_LOAD		0
421 #define	VDEV_ALLOC_ADD		1
422 #define	VDEV_ALLOC_SPARE	2
423 #define	VDEV_ALLOC_L2CACHE	3
424 #define	VDEV_ALLOC_ROOTPOOL	4
425 #define	VDEV_ALLOC_SPLIT	5
426 #define	VDEV_ALLOC_ATTACH	6
427 
428 /*
429  * Allocate or free a vdev
430  */
431 extern vdev_t *vdev_alloc_common(spa_t *spa, uint_t id, uint64_t guid,
432     vdev_ops_t *ops);
433 extern int vdev_alloc(spa_t *spa, vdev_t **vdp, nvlist_t *config,
434     vdev_t *parent, uint_t id, int alloctype);
435 extern void vdev_free(vdev_t *vd);
436 
437 /*
438  * Add or remove children and parents
439  */
440 extern void vdev_add_child(vdev_t *pvd, vdev_t *cvd);
441 extern void vdev_remove_child(vdev_t *pvd, vdev_t *cvd);
442 extern void vdev_compact_children(vdev_t *pvd);
443 extern vdev_t *vdev_add_parent(vdev_t *cvd, vdev_ops_t *ops);
444 extern void vdev_remove_parent(vdev_t *cvd);
445 
446 /*
447  * vdev sync load and sync
448  */
449 extern boolean_t vdev_log_state_valid(vdev_t *vd);
450 extern int vdev_load(vdev_t *vd);
451 extern int vdev_dtl_load(vdev_t *vd);
452 extern void vdev_sync(vdev_t *vd, uint64_t txg);
453 extern void vdev_sync_done(vdev_t *vd, uint64_t txg);
454 extern void vdev_dirty(vdev_t *vd, int flags, void *arg, uint64_t txg);
455 extern void vdev_dirty_leaves(vdev_t *vd, int flags, uint64_t txg);
456 
457 /*
458  * Available vdev types.
459  */
460 extern vdev_ops_t vdev_root_ops;
461 extern vdev_ops_t vdev_mirror_ops;
462 extern vdev_ops_t vdev_replacing_ops;
463 extern vdev_ops_t vdev_raidz_ops;
464 extern vdev_ops_t vdev_disk_ops;
465 extern vdev_ops_t vdev_file_ops;
466 extern vdev_ops_t vdev_missing_ops;
467 extern vdev_ops_t vdev_hole_ops;
468 extern vdev_ops_t vdev_spare_ops;
469 extern vdev_ops_t vdev_indirect_ops;
470 
471 /*
472  * Common size functions
473  */
474 extern void vdev_default_xlate(vdev_t *vd, const range_seg_t *in,
475     range_seg_t *out);
476 extern uint64_t vdev_default_asize(vdev_t *vd, uint64_t psize);
477 extern uint64_t vdev_get_min_asize(vdev_t *vd);
478 extern void vdev_set_min_asize(vdev_t *vd);
479 
480 /*
481  * Global variables
482  */
483 extern int vdev_standard_sm_blksz;
484 /* zdb uses this tunable, so it must be declared here to make lint happy. */
485 extern int zfs_vdev_cache_size;
486 
487 /*
488  * Functions from vdev_indirect.c
489  */
490 extern void vdev_indirect_sync_obsolete(vdev_t *vd, dmu_tx_t *tx);
491 extern boolean_t vdev_indirect_should_condense(vdev_t *vd);
492 extern void spa_condense_indirect_start_sync(vdev_t *vd, dmu_tx_t *tx);
493 extern int vdev_obsolete_sm_object(vdev_t *vd);
494 extern boolean_t vdev_obsolete_counts_are_precise(vdev_t *vd);
495 
496 /*
497  * Other miscellaneous functions
498  */
499 int vdev_checkpoint_sm_object(vdev_t *vd);
500 
501 /*
502  * The vdev_buf_t is used to translate between zio_t and buf_t, and back again.
503  */
504 typedef struct vdev_buf {
505 	buf_t	vb_buf;		/* buffer that describes the io */
506 	zio_t	*vb_io;		/* pointer back to the original zio_t */
507 } vdev_buf_t;
508 
509 #ifdef	__cplusplus
510 }
511 #endif
512 
513 #endif	/* _SYS_VDEV_IMPL_H */
514