drivers/md/md.h

   1 /*
   2    md_k.h : kernel internal structure of the Linux MD driver
   3           Copyright (C) 1996-98 Ingo Molnar, Gadi Oxman
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    You should have received a copy of the GNU General Public License
  11    (for example /usr/src/linux/COPYING); if not, write to the Free
  12    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  13 */
  14
  15 #ifndef _MD_MD_H
  16 #define _MD_MD_H
  17
  18 #include <linux/blkdev.h>
  19 #include <linux/kobject.h>
  20 #include <linux/list.h>
  21 #include <linux/mm.h>
  22 #include <linux/mutex.h>
  23 #include <linux/timer.h>
  24 #include <linux/wait.h>
  25 #include <linux/workqueue.h>
  26
  27 #define MaxSector (~(sector_t)0)
  28
  29 typedef struct mddev_s mddev_t;
  30 typedef struct mdk_rdev_s mdk_rdev_t;
  31
  32 /* Bad block numbers are stored sorted in a single page.
  33  * 64bits is used for each block or extent.
  34  * 54 bits are sector number, 9 bits are extent size,
  35  * 1 bit is an 'acknowledged' flag.
  36  */
  37 #define MD_MAX_BADBLOCKS        (PAGE_SIZE/8)
  38
  39 /*
  40  * MD's 'extended' device
  41  */
  42 struct mdk_rdev_s
  43 {
  44         struct list_head same_set;      /* RAID devices within the same set */
  45
  46         sector_t sectors;               /* Device size (in 512bytes sectors) */
  47         mddev_t *mddev;                 /* RAID array if running */
  48         int last_events;                /* IO event timestamp */
  49
  50         /*
  51          * If meta_bdev is non-NULL, it means that a separate device is
  52          * being used to store the metadata (superblock/bitmap) which
  53          * would otherwise be contained on the same device as the data (bdev).
  54          */
  55         struct block_device *meta_bdev;
  56         struct block_device *bdev;      /* block device handle */
  57
  58         struct page     *sb_page;
  59         int             sb_loaded;
  60         __u64           sb_events;
  61         sector_t        data_offset;    /* start of data in array */
  62         sector_t        sb_start;       /* offset of the super block (in 512byte sectors) */
  63         int             sb_size;        /* bytes in the superblock */
  64         int             preferred_minor;        /* autorun support */
  65
  66         struct kobject  kobj;
  67
  68         /* A device can be in one of three states based on two flags:
  69          * Not working:   faulty==1 in_sync==0
  70          * Fully working: faulty==0 in_sync==1
  71          * Working, but not
  72          * in sync with array
  73          *                faulty==0 in_sync==0
  74          *
  75          * It can never have faulty==1, in_sync==1
  76          * This reduces the burden of testing multiple flags in many cases
  77          */
  78
  79         unsigned long   flags;
  80 #define Faulty          1               /* device is known to have a fault */
  81 #define In_sync         2               /* device is in_sync with rest of array */
  82 #define WriteMostly     4               /* Avoid reading if at all possible */
  83 #define AutoDetected    7               /* added by auto-detect */
  84 #define Blocked         8               /* An error occurred on an externally
  85                                          * managed array, don't allow writes
  86                                          * until it is cleared */
  87         wait_queue_head_t blocked_wait;
  88
  89         int desc_nr;                    /* descriptor index in the superblock */
  90         int raid_disk;                  /* role of device in array */
  91         int new_raid_disk;              /* role that the device will have in
  92                                          * the array after a level-change completes.
  93                                          */
  94         int saved_raid_disk;            /* role that device used to have in the
  95                                          * array and could again if we did a partial
  96                                          * resync from the bitmap
  97                                          */
  98         sector_t        recovery_offset;/* If this device has been partially
  99                                          * recovered, this is where we were
 100                                          * up to.
 101                                          */
 102
 103         atomic_t        nr_pending;     /* number of pending requests.
 104                                          * only maintained for arrays that
 105                                          * support hot removal
 106                                          */
 107         atomic_t        read_errors;    /* number of consecutive read errors that
 108                                          * we have tried to ignore.
 109                                          */
 110         struct timespec last_read_error;        /* monotonic time since our
 111                                                  * last read error
 112                                                  */
 113         atomic_t        corrected_errors; /* number of corrected read errors,
 114                                            * for reporting to userspace and storing
 115                                            * in superblock.
 116                                            */
 117         struct work_struct del_work;    /* used for delayed sysfs removal */
 118
 119         struct sysfs_dirent *sysfs_state; /* handle for 'state'
 120                                            * sysfs entry */
 121
 122         struct badblocks {
 123                 int     count;          /* count of bad blocks */
 124                 int     shift;          /* shift from sectors to block size
 125                                          * a -ve shift means badblocks are
 126                                          * disabled.*/
 127                 u64     *page;          /* badblock list */
 128                 int     changed;
 129                 seqlock_t lock;
 130         } badblocks;
 131 };
 132
 133 #define BB_LEN_MASK     (0x00000000000001FFULL)
 134 #define BB_OFFSET_MASK  (0x7FFFFFFFFFFFFE00ULL)
 135 #define BB_ACK_MASK     (0x8000000000000000ULL)
 136 #define BB_MAX_LEN      512
 137 #define BB_OFFSET(x)    (((x) & BB_OFFSET_MASK) >> 9)
 138 #define BB_LEN(x)       (((x) & BB_LEN_MASK) + 1)
 139 #define BB_ACK(x)       (!!((x) & BB_ACK_MASK))
 140 #define BB_MAKE(a, l, ack) (((a)<<9) | ((l)-1) | ((u64)(!!(ack)) << 63))
 141
 142 extern int md_is_badblock(struct badblocks *bb, sector_t s, int sectors,
 143                           sector_t *first_bad, int *bad_sectors);
 144 static inline int is_badblock(mdk_rdev_t *rdev, sector_t s, int sectors,
 145                               sector_t *first_bad, int *bad_sectors)
 146 {
 147         if (unlikely(rdev->badblocks.count)) {
 148                 int rv = md_is_badblock(&rdev->badblocks, rdev->data_offset + s,
 149                                         sectors,
 150                                         first_bad, bad_sectors);
 151                 if (rv)
 152                         *first_bad -= rdev->data_offset;
 153                 return rv;
 154         }
 155         return 0;
 156 }
 157 extern int rdev_set_badblocks(mdk_rdev_t *rdev, sector_t s, int sectors,
 158                               int acknowledged);
 159 extern int rdev_clear_badblocks(mdk_rdev_t *rdev, sector_t s, int sectors);
 160 extern void md_ack_all_badblocks(struct badblocks *bb);
 161
 162 struct mddev_s
 163 {
 164         void                            *private;
 165         struct mdk_personality          *pers;
 166         dev_t                           unit;
 167         int                             md_minor;
 168         struct list_head                disks;
 169         unsigned long                   flags;
 170 #define MD_CHANGE_DEVS  0       /* Some device status has changed */
 171 #define MD_CHANGE_CLEAN 1       /* transition to or from 'clean' */
 172 #define MD_CHANGE_PENDING 2     /* switch from 'clean' to 'active' in progress */
 173 #define MD_ARRAY_FIRST_USE 3    /* First use of array, needs initialization */
 174
 175         int                             suspended;
 176         atomic_t                        active_io;
 177         int                             ro;
 178         int                             sysfs_active; /* set when sysfs deletes
 179                                                        * are happening, so run/
 180                                                        * takeover/stop are not safe
 181                                                        */
 182         int                             ready; /* See when safe to pass
 183                                                 * IO requests down */
 184         struct gendisk                  *gendisk;
 185
 186         struct kobject                  kobj;
 187         int                             hold_active;
 188 #define UNTIL_IOCTL     1
 189 #define UNTIL_STOP      2
 190
 191         /* Superblock information */
 192         int                             major_version,
 193                                         minor_version,
 194                                         patch_version;
 195         int                             persistent;
 196         int                             external;       /* metadata is
 197                                                          * managed externally */
 198         char                            metadata_type[17]; /* externally set*/
 199         int                             chunk_sectors;
 200         time_t                          ctime, utime;
 201         int                             level, layout;
 202         char                            clevel[16];
 203         int                             raid_disks;
 204         int                             max_disks;
 205         sector_t                        dev_sectors;    /* used size of
 206                                                          * component devices */
 207         sector_t                        array_sectors; /* exported array size */
 208         int                             external_size; /* size managed
 209                                                         * externally */
 210         __u64                           events;
 211         /* If the last 'event' was simply a clean->dirty transition, and
 212          * we didn't write it to the spares, then it is safe and simple
 213          * to just decrement the event count on a dirty->clean transition.
 214          * So we record that possibility here.
 215          */
 216         int                             can_decrease_events;
 217
 218         char                            uuid[16];
 219
 220         /* If the array is being reshaped, we need to record the
 221          * new shape and an indication of where we are up to.
 222          * This is written to the superblock.
 223          * If reshape_position is MaxSector, then no reshape is happening (yet).
 224          */
 225         sector_t                        reshape_position;
 226         int                             delta_disks, new_level, new_layout;
 227         int                             new_chunk_sectors;
 228
 229         atomic_t                        plug_cnt;       /* If device is expecting
 230                                                          * more bios soon.
 231                                                          */
 232         struct mdk_thread_s             *thread;        /* management thread */
 233         struct mdk_thread_s             *sync_thread;   /* doing resync or reconstruct */
 234         sector_t                        curr_resync;    /* last block scheduled */
 235         /* As resync requests can complete out of order, we cannot easily track
 236          * how much resync has been completed.  So we occasionally pause until
 237          * everything completes, then set curr_resync_completed to curr_resync.
 238          * As such it may be well behind the real resync mark, but it is a value
 239          * we are certain of.
 240          */
 241         sector_t                        curr_resync_completed;
 242         unsigned long                   resync_mark;    /* a recent timestamp */
 243         sector_t                        resync_mark_cnt;/* blocks written at resync_mark */
 244         sector_t                        curr_mark_cnt; /* blocks scheduled now */
 245
 246         sector_t                        resync_max_sectors; /* may be set by personality */
 247
 248         sector_t                        resync_mismatches; /* count of sectors where
 249                                                             * parity/replica mismatch found
 250                                                             */
 251
 252         /* allow user-space to request suspension of IO to regions of the array */
 253         sector_t                        suspend_lo;
 254         sector_t                        suspend_hi;
 255         /* if zero, use the system-wide default */
 256         int                             sync_speed_min;
 257         int                             sync_speed_max;
 258
 259         /* resync even though the same disks are shared among md-devices */
 260         int                             parallel_resync;
 261
 262         int                             ok_start_degraded;
 263         /* recovery/resync flags
 264          * NEEDED:   we might need to start a resync/recover
 265          * RUNNING:  a thread is running, or about to be started
 266          * SYNC:     actually doing a resync, not a recovery
 267          * RECOVER:  doing recovery, or need to try it.
 268          * INTR:     resync needs to be aborted for some reason
 269          * DONE:     thread is done and is waiting to be reaped
 270          * REQUEST:  user-space has requested a sync (used with SYNC)
 271          * CHECK:    user-space request for check-only, no repair
 272          * RESHAPE:  A reshape is happening
 273          *
 274          * If neither SYNC or RESHAPE are set, then it is a recovery.
 275          */
 276 #define MD_RECOVERY_RUNNING     0
 277 #define MD_RECOVERY_SYNC        1
 278 #define MD_RECOVERY_RECOVER     2
 279 #define MD_RECOVERY_INTR        3
 280 #define MD_RECOVERY_DONE        4
 281 #define MD_RECOVERY_NEEDED      5
 282 #define MD_RECOVERY_REQUESTED   6
 283 #define MD_RECOVERY_CHECK       7
 284 #define MD_RECOVERY_RESHAPE     8
 285 #define MD_RECOVERY_FROZEN      9
 286
 287         unsigned long                   recovery;
 288         /* If a RAID personality determines that recovery (of a particular
 289          * device) will fail due to a read error on the source device, it
 290          * takes a copy of this number and does not attempt recovery again
 291          * until this number changes.
 292          */
 293         int                             recovery_disabled;
 294
 295         int                             in_sync;        /* know to not need resync */
 296         /* 'open_mutex' avoids races between 'md_open' and 'do_md_stop', so
 297          * that we are never stopping an array while it is open.
 298          * 'reconfig_mutex' protects all other reconfiguration.
 299          * These locks are separate due to conflicting interactions
 300          * with bdev->bd_mutex.
 301          * Lock ordering is:
 302          *  reconfig_mutex -> bd_mutex : e.g. do_md_run -> revalidate_disk
 303          *  bd_mutex -> open_mutex:  e.g. __blkdev_get -> md_open
 304          */
 305         struct mutex                    open_mutex;
 306         struct mutex                    reconfig_mutex;
 307         atomic_t                        active;         /* general refcount */
 308         atomic_t                        openers;        /* number of active opens */
 309
 310         int                             changed;        /* True if we might need to
 311                                                          * reread partition info */
 312         int                             degraded;       /* whether md should consider
 313                                                          * adding a spare
 314                                                          */
 315
 316         atomic_t                        recovery_active; /* blocks scheduled, but not written */
 317         wait_queue_head_t               recovery_wait;
 318         sector_t                        recovery_cp;
 319         sector_t                        resync_min;     /* user requested sync
 320                                                          * starts here */
 321         sector_t                        resync_max;     /* resync should pause
 322                                                          * when it gets here */
 323
 324         struct sysfs_dirent             *sysfs_state;   /* handle for 'array_state'
 325                                                          * file in sysfs.
 326                                                          */
 327         struct sysfs_dirent             *sysfs_action;  /* handle for 'sync_action' */
 328
 329         struct work_struct del_work;    /* used for delayed sysfs removal */
 330
 331         spinlock_t                      write_lock;
 332         wait_queue_head_t               sb_wait;        /* for waiting on superblock updates */
 333         atomic_t                        pending_writes; /* number of active superblock writes */
 334
 335         unsigned int                    safemode;       /* if set, update "clean" superblock
 336                                                          * when no writes pending.
 337                                                          */
 338         unsigned int                    safemode_delay;
 339         struct timer_list               safemode_timer;
 340         atomic_t                        writes_pending;
 341         struct request_queue            *queue; /* for plugging ... */
 342
 343         struct bitmap                   *bitmap; /* the bitmap for the device */
 344         struct {
 345                 struct file             *file; /* the bitmap file */
 346                 loff_t                  offset; /* offset from superblock of
 347                                                  * start of bitmap. May be
 348                                                  * negative, but not '0'
 349                                                  * For external metadata, offset
 350                                                  * from start of device.
 351                                                  */
 352                 loff_t                  default_offset; /* this is the offset to use when
 353                                                          * hot-adding a bitmap.  It should
 354                                                          * eventually be settable by sysfs.
 355                                                          */
 356                 struct mutex            mutex;
 357                 unsigned long           chunksize;
 358                 unsigned long           daemon_sleep; /* how many jiffies between updates? */
 359                 unsigned long           max_write_behind; /* write-behind mode */
 360                 int                     external;
 361         } bitmap_info;
 362
 363         atomic_t                        max_corr_read_errors; /* max read retries */
 364         struct list_head                all_mddevs;
 365
 366         struct attribute_group          *to_remove;
 367
 368         struct bio_set                  *bio_set;
 369
 370         /* Generic flush handling.
 371          * The last to finish preflush schedules a worker to submit
 372          * the rest of the request (without the REQ_FLUSH flag).
 373          */
 374         struct bio *flush_bio;
 375         atomic_t flush_pending;
 376         struct work_struct flush_work;
 377         struct work_struct event_work;  /* used by dm to report failure event */
 378         void (*sync_super)(mddev_t *mddev, mdk_rdev_t *rdev);
 379 };
 380
 381
 382 static inline void rdev_dec_pending(mdk_rdev_t *rdev, mddev_t *mddev)
 383 {
 384         int faulty = test_bit(Faulty, &rdev->flags);
 385         if (atomic_dec_and_test(&rdev->nr_pending) && faulty)
 386                 set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 387 }
 388
 389 static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
 390 {
 391         atomic_add(nr_sectors, &bdev->bd_contains->bd_disk->sync_io);
 392 }
 393
 394 struct mdk_personality
 395 {
 396         char *name;
 397         int level;
 398         struct list_head list;
 399         struct module *owner;
 400         int (*make_request)(mddev_t *mddev, struct bio *bio);
 401         int (*run)(mddev_t *mddev);
 402         int (*stop)(mddev_t *mddev);
 403         void (*status)(struct seq_file *seq, mddev_t *mddev);
 404         /* error_handler must set ->faulty and clear ->in_sync
 405          * if appropriate, and should abort recovery if needed
 406          */
 407         void (*error_handler)(mddev_t *mddev, mdk_rdev_t *rdev);
 408         int (*hot_add_disk) (mddev_t *mddev, mdk_rdev_t *rdev);
 409         int (*hot_remove_disk) (mddev_t *mddev, int number);
 410         int (*spare_active) (mddev_t *mddev);
 411         sector_t (*sync_request)(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster);
 412         int (*resize) (mddev_t *mddev, sector_t sectors);
 413         sector_t (*size) (mddev_t *mddev, sector_t sectors, int raid_disks);
 414         int (*check_reshape) (mddev_t *mddev);
 415         int (*start_reshape) (mddev_t *mddev);
 416         void (*finish_reshape) (mddev_t *mddev);
 417         /* quiesce moves between quiescence states
 418          * 0 - fully active
 419          * 1 - no new requests allowed
 420          * others - reserved
 421          */
 422         void (*quiesce) (mddev_t *mddev, int state);
 423         /* takeover is used to transition an array from one
 424          * personality to another.  The new personality must be able
 425          * to handle the data in the current layout.
 426          * e.g. 2drive raid1 -> 2drive raid5
 427          *      ndrive raid5 -> degraded n+1drive raid6 with special layout
 428          * If the takeover succeeds, a new 'private' structure is returned.
 429          * This needs to be installed and then ->run used to activate the
 430          * array.
 431          */
 432         void *(*takeover) (mddev_t *mddev);
 433 };
 434
 435
 436 struct md_sysfs_entry {
 437         struct attribute attr;
 438         ssize_t (*show)(mddev_t *, char *);
 439         ssize_t (*store)(mddev_t *, const char *, size_t);
 440 };
 441 extern struct attribute_group md_bitmap_group;
 442
 443 static inline struct sysfs_dirent *sysfs_get_dirent_safe(struct sysfs_dirent *sd, char *name)
 444 {
 445         if (sd)
 446                 return sysfs_get_dirent(sd, NULL, name);
 447         return sd;
 448 }
 449 static inline void sysfs_notify_dirent_safe(struct sysfs_dirent *sd)
 450 {
 451         if (sd)
 452                 sysfs_notify_dirent(sd);
 453 }
 454
 455 static inline char * mdname (mddev_t * mddev)
 456 {
 457         return mddev->gendisk ? mddev->gendisk->disk_name : "mdX";
 458 }
 459
 460 static inline int sysfs_link_rdev(mddev_t *mddev, mdk_rdev_t *rdev)
 461 {
 462         char nm[20];
 463         sprintf(nm, "rd%d", rdev->raid_disk);
 464         return sysfs_create_link(&mddev->kobj, &rdev->kobj, nm);
 465 }
 466
 467 static inline void sysfs_unlink_rdev(mddev_t *mddev, mdk_rdev_t *rdev)
 468 {
 469         char nm[20];
 470         sprintf(nm, "rd%d", rdev->raid_disk);
 471         sysfs_remove_link(&mddev->kobj, nm);
 472 }
 473
 474 /*
 475  * iterates through some rdev ringlist. It's safe to remove the
 476  * current 'rdev'. Dont touch 'tmp' though.
 477  */
 478 #define rdev_for_each_list(rdev, tmp, head)                             \
 479         list_for_each_entry_safe(rdev, tmp, head, same_set)
 480
 481 /*
 482  * iterates through the 'same array disks' ringlist
 483  */
 484 #define rdev_for_each(rdev, tmp, mddev)                         \
 485         list_for_each_entry_safe(rdev, tmp, &((mddev)->disks), same_set)
 486
 487 #define rdev_for_each_rcu(rdev, mddev)                          \
 488         list_for_each_entry_rcu(rdev, &((mddev)->disks), same_set)
 489
 490 typedef struct mdk_thread_s {
 491         void                    (*run) (mddev_t *mddev);
 492         mddev_t                 *mddev;
 493         wait_queue_head_t       wqueue;
 494         unsigned long           flags;
 495         struct task_struct      *tsk;
 496         unsigned long           timeout;
 497 } mdk_thread_t;
 498
 499 #define THREAD_WAKEUP  0
 500
 501 #define __wait_event_lock_irq(wq, condition, lock, cmd)                 \
 502 do {                                                                    \
 503         wait_queue_t __wait;                                            \
 504         init_waitqueue_entry(&__wait, current);                         \
 505                                                                         \
 506         add_wait_queue(&wq, &__wait);                                   \
 507         for (;;) {                                                      \
 508                 set_current_state(TASK_UNINTERRUPTIBLE);                \
 509                 if (condition)                                          \
 510                         break;                                          \
 511                 spin_unlock_irq(&lock);                                 \
 512                 cmd;                                                    \
 513                 schedule();                                             \
 514                 spin_lock_irq(&lock);                                   \
 515         }                                                               \
 516         current->state = TASK_RUNNING;                                  \
 517         remove_wait_queue(&wq, &__wait);                                \
 518 } while (0)
 519
 520 #define wait_event_lock_irq(wq, condition, lock, cmd)                   \
 521 do {                                                                    \
 522         if (condition)                                                  \
 523                 break;                                                  \
 524         __wait_event_lock_irq(wq, condition, lock, cmd);                \
 525 } while (0)
 526
 527 static inline void safe_put_page(struct page *p)
 528 {
 529         if (p) put_page(p);
 530 }
 531
 532 extern int register_md_personality(struct mdk_personality *p);
 533 extern int unregister_md_personality(struct mdk_personality *p);
 534 extern mdk_thread_t * md_register_thread(void (*run) (mddev_t *mddev),
 535                                 mddev_t *mddev, const char *name);
 536 extern void md_unregister_thread(mdk_thread_t *thread);
 537 extern void md_wakeup_thread(mdk_thread_t *thread);
 538 extern void md_check_recovery(mddev_t *mddev);
 539 extern void md_write_start(mddev_t *mddev, struct bio *bi);
 540 extern void md_write_end(mddev_t *mddev);
 541 extern void md_done_sync(mddev_t *mddev, int blocks, int ok);
 542 extern void md_error(mddev_t *mddev, mdk_rdev_t *rdev);
 543
 544 extern int mddev_congested(mddev_t *mddev, int bits);
 545 extern void md_flush_request(mddev_t *mddev, struct bio *bio);
 546 extern void md_super_write(mddev_t *mddev, mdk_rdev_t *rdev,
 547                            sector_t sector, int size, struct page *page);
 548 extern void md_super_wait(mddev_t *mddev);
 549 extern int sync_page_io(mdk_rdev_t *rdev, sector_t sector, int size,
 550                         struct page *page, int rw, bool metadata_op);
 551 extern void md_do_sync(mddev_t *mddev);
 552 extern void md_new_event(mddev_t *mddev);
 553 extern int md_allow_write(mddev_t *mddev);
 554 extern void md_wait_for_blocked_rdev(mdk_rdev_t *rdev, mddev_t *mddev);
 555 extern void md_set_array_sectors(mddev_t *mddev, sector_t array_sectors);
 556 extern int md_check_no_bitmap(mddev_t *mddev);
 557 extern int md_integrity_register(mddev_t *mddev);
 558 extern void md_integrity_add_rdev(mdk_rdev_t *rdev, mddev_t *mddev);
 559 extern int strict_strtoul_scaled(const char *cp, unsigned long *res, int scale);
 560 extern void restore_bitmap_write_access(struct file *file);
 561
 562 extern void mddev_init(mddev_t *mddev);
 563 extern int md_run(mddev_t *mddev);
 564 extern void md_stop(mddev_t *mddev);
 565 extern void md_stop_writes(mddev_t *mddev);
 566 extern int md_rdev_init(mdk_rdev_t *rdev);
 567
 568 extern void mddev_suspend(mddev_t *mddev);
 569 extern void mddev_resume(mddev_t *mddev);
 570 extern struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask,
 571                                    mddev_t *mddev);
 572 extern struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
 573                                    mddev_t *mddev);
 574 extern int mddev_check_plugged(mddev_t *mddev);
 575 #endif /* _MD_MD_H */