sys/cddl/contrib/opensolaris/uts/common/fs/zfs/sys/vdev_impl.h

   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, 2017 by Delphix. All rights reserved.
  24  */
  25
  26 #ifndef _SYS_VDEV_IMPL_H
  27 #define _SYS_VDEV_IMPL_H
  28
  29 #include <sys/avl.h>
  30 #include <sys/bpobj.h>
  31 #include <sys/dmu.h>
  32 #include <sys/metaslab.h>
  33 #include <sys/nvpair.h>
  34 #include <sys/space_map.h>
  35 #include <sys/vdev.h>
  36 #include <sys/dkio.h>
  37 #include <sys/uberblock_impl.h>
  38 #include <sys/vdev_indirect_mapping.h>
  39 #include <sys/vdev_indirect_births.h>
  40 #include <sys/vdev_removal.h>
  41
  42 #ifdef  __cplusplus
  43 extern "C" {
  44 #endif
  45
  46 /*
  47  * Virtual device descriptors.
  48  *
  49  * All storage pool operations go through the virtual device framework,
  50  * which provides data replication and I/O scheduling.
  51  */
  52
  53 /*
  54  * Forward declarations that lots of things need.
  55  */
  56 typedef struct vdev_queue vdev_queue_t;
  57 typedef struct vdev_cache vdev_cache_t;
  58 typedef struct vdev_cache_entry vdev_cache_entry_t;
  59 struct abd;
  60
  61 extern int zfs_vdev_queue_depth_pct;
  62 extern uint32_t zfs_vdev_async_write_max_active;
  63
  64 /*
  65  * Virtual device operations
  66  */
  67 typedef int     vdev_open_func_t(vdev_t *vd, uint64_t *size, uint64_t *max_size,
  68     uint64_t *logical_ashift, uint64_t *physical_ashift);
  69 typedef void    vdev_close_func_t(vdev_t *vd);
  70 typedef uint64_t vdev_asize_func_t(vdev_t *vd, uint64_t psize);
  71 typedef void    vdev_io_start_func_t(zio_t *zio);
  72 typedef void    vdev_io_done_func_t(zio_t *zio);
  73 typedef void    vdev_state_change_func_t(vdev_t *vd, int, int);
  74 typedef boolean_t vdev_need_resilver_func_t(vdev_t *vd, uint64_t, size_t);
  75 typedef void    vdev_hold_func_t(vdev_t *vd);
  76 typedef void    vdev_rele_func_t(vdev_t *vd);
  77
  78 typedef void    vdev_remap_cb_t(uint64_t inner_offset, vdev_t *vd,
  79     uint64_t offset, uint64_t size, void *arg);
  80 typedef void    vdev_remap_func_t(vdev_t *vd, uint64_t offset, uint64_t size,
  81     vdev_remap_cb_t callback, void *arg);
  82
  83 typedef struct vdev_ops {
  84         vdev_open_func_t                *vdev_op_open;
  85         vdev_close_func_t               *vdev_op_close;
  86         vdev_asize_func_t               *vdev_op_asize;
  87         vdev_io_start_func_t            *vdev_op_io_start;
  88         vdev_io_done_func_t             *vdev_op_io_done;
  89         vdev_state_change_func_t        *vdev_op_state_change;
  90         vdev_need_resilver_func_t       *vdev_op_need_resilver;
  91         vdev_hold_func_t                *vdev_op_hold;
  92         vdev_rele_func_t                *vdev_op_rele;
  93         vdev_remap_func_t               *vdev_op_remap;
  94         char                            vdev_op_type[16];
  95         boolean_t                       vdev_op_leaf;
  96 } vdev_ops_t;
  97
  98 /*
  99  * Virtual device properties
 100  */
 101 struct vdev_cache_entry {
 102         struct abd      *ve_abd;
 103         uint64_t        ve_offset;
 104         uint64_t        ve_lastused;
 105         avl_node_t      ve_offset_node;
 106         avl_node_t      ve_lastused_node;
 107         uint32_t        ve_hits;
 108         uint16_t        ve_missed_update;
 109         zio_t           *ve_fill_io;
 110 };
 111
 112 struct vdev_cache {
 113         avl_tree_t      vc_offset_tree;
 114         avl_tree_t      vc_lastused_tree;
 115         kmutex_t        vc_lock;
 116 };
 117
 118 typedef struct vdev_queue_class {
 119         uint32_t        vqc_active;
 120
 121         /*
 122          * Sorted by offset or timestamp, depending on if the queue is
 123          * LBA-ordered vs FIFO.
 124          */
 125         avl_tree_t      vqc_queued_tree;
 126 } vdev_queue_class_t;
 127
 128 struct vdev_queue {
 129         vdev_t          *vq_vdev;
 130         vdev_queue_class_t vq_class[ZIO_PRIORITY_NUM_QUEUEABLE];
 131         avl_tree_t      vq_active_tree;
 132         avl_tree_t      vq_read_offset_tree;
 133         avl_tree_t      vq_write_offset_tree;
 134         uint64_t        vq_last_offset;
 135         hrtime_t        vq_io_complete_ts; /* time last i/o completed */
 136         kmutex_t        vq_lock;
 137         uint64_t        vq_lastoffset;
 138 };
 139
 140 /*
 141  * On-disk indirect vdev state.
 142  *
 143  * An indirect vdev is described exclusively in the MOS config of a pool.
 144  * The config for an indirect vdev includes several fields, which are
 145  * accessed in memory by a vdev_indirect_config_t.
 146  */
 147 typedef struct vdev_indirect_config {
 148         /*
 149          * Object (in MOS) which contains the indirect mapping. This object
 150          * contains an array of vdev_indirect_mapping_entry_phys_t ordered by
 151          * vimep_src. The bonus buffer for this object is a
 152          * vdev_indirect_mapping_phys_t. This object is allocated when a vdev
 153          * removal is initiated.
 154          *
 155          * Note that this object can be empty if none of the data on the vdev
 156          * has been copied yet.
 157          */
 158         uint64_t        vic_mapping_object;
 159
 160         /*
 161          * Object (in MOS) which contains the birth times for the mapping
 162          * entries. This object contains an array of
 163          * vdev_indirect_birth_entry_phys_t sorted by vibe_offset. The bonus
 164          * buffer for this object is a vdev_indirect_birth_phys_t. This object
 165          * is allocated when a vdev removal is initiated.
 166          *
 167          * Note that this object can be empty if none of the vdev has yet been
 168          * copied.
 169          */
 170         uint64_t        vic_births_object;
 171
 172         /*
 173          * This is the vdev ID which was removed previous to this vdev, or
 174          * UINT64_MAX if there are no previously removed vdevs.
 175          */
 176         uint64_t        vic_prev_indirect_vdev;
 177 } vdev_indirect_config_t;
 178
 179 /*
 180  * Virtual device descriptor
 181  */
 182 struct vdev {
 183         /*
 184          * Common to all vdev types.
 185          */
 186         uint64_t        vdev_id;        /* child number in vdev parent  */
 187         uint64_t        vdev_guid;      /* unique ID for this vdev      */
 188         uint64_t        vdev_guid_sum;  /* self guid + all child guids  */
 189         uint64_t        vdev_orig_guid; /* orig. guid prior to remove   */
 190         uint64_t        vdev_asize;     /* allocatable device capacity  */
 191         uint64_t        vdev_min_asize; /* min acceptable asize         */
 192         uint64_t        vdev_max_asize; /* max acceptable asize         */
 193         uint64_t        vdev_ashift;    /* block alignment shift        */
 194         /*
 195          * Logical block alignment shift
 196          *
 197          * The smallest sized/aligned I/O supported by the device.
 198          */
 199         uint64_t        vdev_logical_ashift;
 200         /*
 201          * Physical block alignment shift
 202          *
 203          * The device supports logical I/Os with vdev_logical_ashift
 204          * size/alignment, but optimum performance will be achieved by
 205          * aligning/sizing requests to vdev_physical_ashift.  Smaller
 206          * requests may be inflated or incur device level read-modify-write
 207          * operations.
 208          *
 209          * May be 0 to indicate no preference (i.e. use vdev_logical_ashift).
 210          */
 211         uint64_t        vdev_physical_ashift;
 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         kmutex_t        vdev_queue_lock; /* protects vdev_queue_depth   */
 250         uint64_t        vdev_top_zap;
 251
 252         /* pool checkpoint related */
 253         space_map_t     *vdev_checkpoint_sm;    /* contains reserved blocks */
 254
 255         /*
 256          * Values stored in the config for an indirect or removing vdev.
 257          */
 258         vdev_indirect_config_t  vdev_indirect_config;
 259
 260         /*
 261          * The vdev_indirect_rwlock protects the vdev_indirect_mapping
 262          * pointer from changing on indirect vdevs (when it is condensed).
 263          * Note that removing (not yet indirect) vdevs have different
 264          * access patterns (the mapping is not accessed from open context,
 265          * e.g. from zio_read) and locking strategy (e.g. svr_lock).
 266          */
 267         krwlock_t vdev_indirect_rwlock;
 268         vdev_indirect_mapping_t *vdev_indirect_mapping;
 269         vdev_indirect_births_t *vdev_indirect_births;
 270
 271         /*
 272          * In memory data structures used to manage the obsolete sm, for
 273          * indirect or removing vdevs.
 274          *
 275          * The vdev_obsolete_segments is the in-core record of the segments
 276          * that are no longer referenced anywhere in the pool (due to
 277          * being freed or remapped and not referenced by any snapshots).
 278          * During a sync, segments are added to vdev_obsolete_segments
 279          * via vdev_indirect_mark_obsolete(); at the end of each sync
 280          * pass, this is appended to vdev_obsolete_sm via
 281          * vdev_indirect_sync_obsolete().  The vdev_obsolete_lock
 282          * protects against concurrent modifications of vdev_obsolete_segments
 283          * from multiple zio threads.
 284          */
 285         kmutex_t        vdev_obsolete_lock;
 286         range_tree_t    *vdev_obsolete_segments;
 287         space_map_t     *vdev_obsolete_sm;
 288
 289         /*
 290          * The queue depth parameters determine how many async writes are
 291          * still pending (i.e. allocated by net yet issued to disk) per
 292          * top-level (vdev_async_write_queue_depth) and the maximum allowed
 293          * (vdev_max_async_write_queue_depth). These values only apply to
 294          * top-level vdevs.
 295          */
 296         uint64_t        vdev_async_write_queue_depth;
 297         uint64_t        vdev_max_async_write_queue_depth;
 298
 299         /*
 300          * Protects the vdev_scan_io_queue field itself as well as the
 301          * structure's contents (when present).
 302          */
 303         kmutex_t                        vdev_scan_io_queue_lock;
 304         struct dsl_scan_io_queue        *vdev_scan_io_queue;
 305
 306         /*
 307          * Leaf vdev state.
 308          */
 309         range_tree_t    *vdev_dtl[DTL_TYPES]; /* dirty time logs        */
 310         space_map_t     *vdev_dtl_sm;   /* dirty time log space map     */
 311         txg_node_t      vdev_dtl_node;  /* per-txg dirty DTL linkage    */
 312         uint64_t        vdev_dtl_object; /* DTL object                  */
 313         uint64_t        vdev_psize;     /* physical device capacity     */
 314         uint64_t        vdev_wholedisk; /* true if this is a whole disk */
 315         uint64_t        vdev_offline;   /* persistent offline state     */
 316         uint64_t        vdev_faulted;   /* persistent faulted state     */
 317         uint64_t        vdev_degraded;  /* persistent degraded state    */
 318         uint64_t        vdev_removed;   /* persistent removed state     */
 319         uint64_t        vdev_resilver_txg; /* persistent resilvering state */
 320         uint64_t        vdev_nparity;   /* number of parity devices for raidz */
 321         char            *vdev_path;     /* vdev path (if any)           */
 322         char            *vdev_devid;    /* vdev devid (if any)          */
 323         char            *vdev_physpath; /* vdev device path (if any)    */
 324         char            *vdev_fru;      /* physical FRU location        */
 325         uint64_t        vdev_not_present; /* not present during import  */
 326         uint64_t        vdev_unspare;   /* unspare when resilvering done */
 327         boolean_t       vdev_nowritecache; /* true if flushwritecache failed */
 328         boolean_t       vdev_notrim;    /* true if trim 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         struct trim_map *vdev_trimmap;  /* map on outstanding trims     */
 345         uint16_t        vdev_rotation_rate; /* rotational rate of the media */
 346 #define VDEV_RATE_UNKNOWN       0
 347 #define VDEV_RATE_NON_ROTATING  1
 348         uint64_t        vdev_leaf_zap;
 349
 350         /*
 351          * For DTrace to work in userland (libzpool) context, these fields must
 352          * remain at the end of the structure.  DTrace will use the kernel's
 353          * CTF definition for 'struct vdev', and since the size of a kmutex_t is
 354          * larger in userland, the offsets for the rest of the fields would be
 355          * incorrect.
 356          */
 357         kmutex_t        vdev_dtl_lock;  /* vdev_dtl_{map,resilver}      */
 358         kmutex_t        vdev_stat_lock; /* vdev_stat                    */
 359         kmutex_t        vdev_probe_lock; /* protects vdev_probe_zio     */
 360 };
 361
 362 #define VDEV_RAIDZ_MAXPARITY    3
 363
 364 #define VDEV_PAD_SIZE           (8 << 10)
 365 /* 2 padding areas (vl_pad1 and vl_pad2) to skip */
 366 #define VDEV_SKIP_SIZE          VDEV_PAD_SIZE * 2
 367 #define VDEV_PHYS_SIZE          (112 << 10)
 368 #define VDEV_UBERBLOCK_RING     (128 << 10)
 369
 370 /* The largest uberblock we support is 8k. */
 371 #define MAX_UBERBLOCK_SHIFT (13)
 372 #define VDEV_UBERBLOCK_SHIFT(vd)        \
 373         MIN(MAX((vd)->vdev_top->vdev_ashift, UBERBLOCK_SHIFT), \
 374             MAX_UBERBLOCK_SHIFT)
 375 #define VDEV_UBERBLOCK_COUNT(vd)        \
 376         (VDEV_UBERBLOCK_RING >> VDEV_UBERBLOCK_SHIFT(vd))
 377 #define VDEV_UBERBLOCK_OFFSET(vd, n)    \
 378         offsetof(vdev_label_t, vl_uberblock[(n) << VDEV_UBERBLOCK_SHIFT(vd)])
 379 #define VDEV_UBERBLOCK_SIZE(vd)         (1ULL << VDEV_UBERBLOCK_SHIFT(vd))
 380
 381 typedef struct vdev_phys {
 382         char            vp_nvlist[VDEV_PHYS_SIZE - sizeof (zio_eck_t)];
 383         zio_eck_t       vp_zbt;
 384 } vdev_phys_t;
 385
 386 typedef struct vdev_label {
 387         char            vl_pad1[VDEV_PAD_SIZE];                 /*  8K */
 388         char            vl_pad2[VDEV_PAD_SIZE];                 /*  8K */
 389         vdev_phys_t     vl_vdev_phys;                           /* 112K */
 390         char            vl_uberblock[VDEV_UBERBLOCK_RING];      /* 128K */
 391 } vdev_label_t;                                                 /* 256K total */
 392
 393 /*
 394  * vdev_dirty() flags
 395  */
 396 #define VDD_METASLAB    0x01
 397 #define VDD_DTL         0x02
 398
 399 /* Offset of embedded boot loader region on each label */
 400 #define VDEV_BOOT_OFFSET        (2 * sizeof (vdev_label_t))
 401 /*
 402  * Size of embedded boot loader region on each label.
 403  * The total size of the first two labels plus the boot area is 4MB.
 404  */
 405 #define VDEV_BOOT_SIZE          (7ULL << 19)                    /* 3.5M */
 406
 407 /*
 408  * Size of label regions at the start and end of each leaf device.
 409  */
 410 #define VDEV_LABEL_START_SIZE   (2 * sizeof (vdev_label_t) + VDEV_BOOT_SIZE)
 411 #define VDEV_LABEL_END_SIZE     (2 * sizeof (vdev_label_t))
 412 #define VDEV_LABELS             4
 413 #define VDEV_BEST_LABEL         VDEV_LABELS
 414
 415 #define VDEV_ALLOC_LOAD         0
 416 #define VDEV_ALLOC_ADD          1
 417 #define VDEV_ALLOC_SPARE        2
 418 #define VDEV_ALLOC_L2CACHE      3
 419 #define VDEV_ALLOC_ROOTPOOL     4
 420 #define VDEV_ALLOC_SPLIT        5
 421 #define VDEV_ALLOC_ATTACH       6
 422
 423 /*
 424  * Allocate or free a vdev
 425  */
 426 extern vdev_t *vdev_alloc_common(spa_t *spa, uint_t id, uint64_t guid,
 427     vdev_ops_t *ops);
 428 extern int vdev_alloc(spa_t *spa, vdev_t **vdp, nvlist_t *config,
 429     vdev_t *parent, uint_t id, int alloctype);
 430 extern void vdev_free(vdev_t *vd);
 431
 432 /*
 433  * Add or remove children and parents
 434  */
 435 extern void vdev_add_child(vdev_t *pvd, vdev_t *cvd);
 436 extern void vdev_remove_child(vdev_t *pvd, vdev_t *cvd);
 437 extern void vdev_compact_children(vdev_t *pvd);
 438 extern vdev_t *vdev_add_parent(vdev_t *cvd, vdev_ops_t *ops);
 439 extern void vdev_remove_parent(vdev_t *cvd);
 440
 441 /*
 442  * vdev sync load and sync
 443  */
 444 extern boolean_t vdev_log_state_valid(vdev_t *vd);
 445 extern int vdev_load(vdev_t *vd);
 446 extern int vdev_dtl_load(vdev_t *vd);
 447 extern void vdev_sync(vdev_t *vd, uint64_t txg);
 448 extern void vdev_sync_done(vdev_t *vd, uint64_t txg);
 449 extern void vdev_dirty(vdev_t *vd, int flags, void *arg, uint64_t txg);
 450 extern void vdev_dirty_leaves(vdev_t *vd, int flags, uint64_t txg);
 451
 452 /*
 453  * Available vdev types.
 454  */
 455 extern vdev_ops_t vdev_root_ops;
 456 extern vdev_ops_t vdev_mirror_ops;
 457 extern vdev_ops_t vdev_replacing_ops;
 458 extern vdev_ops_t vdev_raidz_ops;
 459 #ifdef _KERNEL
 460 extern vdev_ops_t vdev_geom_ops;
 461 #else
 462 extern vdev_ops_t vdev_disk_ops;
 463 #endif
 464 extern vdev_ops_t vdev_file_ops;
 465 extern vdev_ops_t vdev_missing_ops;
 466 extern vdev_ops_t vdev_hole_ops;
 467 extern vdev_ops_t vdev_spare_ops;
 468 extern vdev_ops_t vdev_indirect_ops;
 469
 470 /*
 471  * Common size functions
 472  */
 473 extern uint64_t vdev_default_asize(vdev_t *vd, uint64_t psize);
 474 extern uint64_t vdev_get_min_asize(vdev_t *vd);
 475 extern void vdev_set_min_asize(vdev_t *vd);
 476
 477 /*
 478  * Global variables
 479  */
 480 extern int vdev_standard_sm_blksz;
 481 /* zdb uses this tunable, so it must be declared here to make lint happy. */
 482 extern int zfs_vdev_cache_size;
 483 extern uint_t zfs_geom_probe_vdev_key;
 484
 485 /*
 486  * Functions from vdev_indirect.c
 487  */
 488 extern void vdev_indirect_sync_obsolete(vdev_t *vd, dmu_tx_t *tx);
 489 extern boolean_t vdev_indirect_should_condense(vdev_t *vd);
 490 extern void spa_condense_indirect_start_sync(vdev_t *vd, dmu_tx_t *tx);
 491 extern int vdev_obsolete_sm_object(vdev_t *vd);
 492 extern boolean_t vdev_obsolete_counts_are_precise(vdev_t *vd);
 493
 494 #ifdef illumos
 495 /*
 496  * Other miscellaneous functions
 497  */
 498 int vdev_checkpoint_sm_object(vdev_t *vd);
 499
 500 /*
 501  * The vdev_buf_t is used to translate between zio_t and buf_t, and back again.
 502  */
 503 typedef struct vdev_buf {
 504         buf_t   vb_buf;         /* buffer that describes the io */
 505         zio_t   *vb_io;         /* pointer back to the original zio_t */
 506 } vdev_buf_t;
 507 #endif
 508
 509 #ifdef  __cplusplus
 510 }
 511 #endif
 512
 513 #endif  /* _SYS_VDEV_IMPL_H */