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, *bb_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
 131                 sector_t sector;
 132                 sector_t size;          /* in sectors */
 133         } badblocks;
 134 };
 135
 136 #define BB_LEN_MASK     (0x00000000000001FFULL)
 137 #define BB_OFFSET_MASK  (0x7FFFFFFFFFFFFE00ULL)
 138 #define BB_ACK_MASK     (0x8000000000000000ULL)
 139 #define BB_MAX_LEN      512
 140 #define BB_OFFSET(x)    (((x) & BB_OFFSET_MASK) >> 9)
 141 #define BB_LEN(x)       (((x) & BB_LEN_MASK) + 1)
 142 #define BB_ACK(x)       (!!((x) & BB_ACK_MASK))
 143 #define BB_MAKE(a, l, ack) (((a)<<9) | ((l)-1) | ((u64)(!!(ack)) << 63))
 144
 145 extern int md_is_badblock(struct badblocks *bb, sector_t s, int sectors,
 146                           sector_t *first_bad, int *bad_sectors);
 147 static inline int is_badblock(mdk_rdev_t *rdev, sector_t s, int sectors,
 148                               sector_t *first_bad, int *bad_sectors)
 149 {
 150         if (unlikely(rdev->badblocks.count)) {
 151                 int rv = md_is_badblock(&rdev->badblocks, rdev->data_offset + s,
 152                                         sectors,
 153                                         first_bad, bad_sectors);
 154                 if (rv)
 155                         *first_bad -= rdev->data_offset;
 156                 return rv;
 157         }
 158         return 0;
 159 }
 160 extern int rdev_set_badblocks(mdk_rdev_t *rdev, sector_t s, int sectors,
 161                               int acknowledged);
 162 extern int rdev_clear_badblocks(mdk_rdev_t *rdev, sector_t s, int sectors);
 163 extern void md_ack_all_badblocks(struct badblocks *bb);
 164
 165 struct mddev_s
 166 {
 167         void                            *private;
 168         struct mdk_personality          *pers;
 169         dev_t                           unit;
 170         int                             md_minor;
 171         struct list_head                disks;
 172         unsigned long                   flags;
 173 #define MD_CHANGE_DEVS  0       /* Some device status has changed */
 174 #define MD_CHANGE_CLEAN 1       /* transition to or from 'clean' */
 175 #define MD_CHANGE_PENDING 2     /* switch from 'clean' to 'active' in progress */
 176 #define MD_ARRAY_FIRST_USE 3    /* First use of array, needs initialization */
 177
 178         int                             suspended;
 179         atomic_t                        active_io;
 180         int                             ro;
 181         int                             sysfs_active; /* set when sysfs deletes
 182                                                        * are happening, so run/
 183                                                        * takeover/stop are not safe
 184                                                        */
 185         int                             ready; /* See when safe to pass
 186                                                 * IO requests down */
 187         struct gendisk                  *gendisk;
 188
 189         struct kobject                  kobj;
 190         int                             hold_active;
 191 #define UNTIL_IOCTL     1
 192 #define UNTIL_STOP      2
 193
 194         /* Superblock information */
 195         int                             major_version,
 196                                         minor_version,
 197                                         patch_version;
 198         int                             persistent;
 199         int                             external;       /* metadata is
 200                                                          * managed externally */
 201         char                            metadata_type[17]; /* externally set*/
 202         int                             chunk_sectors;
 203         time_t                          ctime, utime;
 204         int                             level, layout;
 205         char                            clevel[16];
 206         int                             raid_disks;
 207         int                             max_disks;
 208         sector_t                        dev_sectors;    /* used size of
 209                                                          * component devices */
 210         sector_t                        array_sectors; /* exported array size */
 211         int                             external_size; /* size managed
 212                                                         * externally */
 213         __u64                           events;
 214         /* If the last 'event' was simply a clean->dirty transition, and
 215          * we didn't write it to the spares, then it is safe and simple
 216          * to just decrement the event count on a dirty->clean transition.
 217          * So we record that possibility here.
 218          */
 219         int                             can_decrease_events;
 220
 221         char                            uuid[16];
 222
 223         /* If the array is being reshaped, we need to record the
 224          * new shape and an indication of where we are up to.
 225          * This is written to the superblock.
 226          * If reshape_position is MaxSector, then no reshape is happening (yet).
 227          */
 228         sector_t                        reshape_position;
 229         int                             delta_disks, new_level, new_layout;
 230         int                             new_chunk_sectors;
 231
 232         atomic_t                        plug_cnt;       /* If device is expecting
 233                                                          * more bios soon.
 234                                                          */
 235         struct mdk_thread_s             *thread;        /* management thread */
 236         struct mdk_thread_s             *sync_thread;   /* doing resync or reconstruct */
 237         sector_t                        curr_resync;    /* last block scheduled */
 238         /* As resync requests can complete out of order, we cannot easily track
 239          * how much resync has been completed.  So we occasionally pause until
 240          * everything completes, then set curr_resync_completed to curr_resync.
 241          * As such it may be well behind the real resync mark, but it is a value
 242          * we are certain of.
 243          */
 244         sector_t                        curr_resync_completed;
 245         unsigned long                   resync_mark;    /* a recent timestamp */
 246         sector_t                        resync_mark_cnt;/* blocks written at resync_mark */
 247         sector_t                        curr_mark_cnt; /* blocks scheduled now */
 248
 249         sector_t                        resync_max_sectors; /* may be set by personality */
 250
 251         sector_t                        resync_mismatches; /* count of sectors where
 252                                                             * parity/replica mismatch found
 253                                                             */
 254
 255         /* allow user-space to request suspension of IO to regions of the array */
 256         sector_t                        suspend_lo;
 257         sector_t                        suspend_hi;
 258         /* if zero, use the system-wide default */
 259         int                             sync_speed_min;
 260         int                             sync_speed_max;
 261
 262         /* resync even though the same disks are shared among md-devices */
 263         int                             parallel_resync;
 264
 265         int                             ok_start_degraded;
 266         /* recovery/resync flags
 267          * NEEDED:   we might need to start a resync/recover
 268          * RUNNING:  a thread is running, or about to be started
 269          * SYNC:     actually doing a resync, not a recovery
 270          * RECOVER:  doing recovery, or need to try it.
 271          * INTR:     resync needs to be aborted for some reason
 272          * DONE:     thread is done and is waiting to be reaped
 273          * REQUEST:  user-space has requested a sync (used with SYNC)
 274          * CHECK:    user-space request for check-only, no repair
 275          * RESHAPE:  A reshape is happening
 276          *
 277          * If neither SYNC or RESHAPE are set, then it is a recovery.
 278          */
 279 #define MD_RECOVERY_RUNNING     0
 280 #define MD_RECOVERY_SYNC        1
 281 #define MD_RECOVERY_RECOVER     2
 282 #define MD_RECOVERY_INTR        3
 283 #define MD_RECOVERY_DONE        4
 284 #define MD_RECOVERY_NEEDED      5
 285 #define MD_RECOVERY_REQUESTED   6
 286 #define MD_RECOVERY_CHECK       7
 287 #define MD_RECOVERY_RESHAPE     8
 288 #define MD_RECOVERY_FROZEN      9
 289
 290         unsigned long                   recovery;
 291         /* If a RAID personality determines that recovery (of a particular
 292          * device) will fail due to a read error on the source device, it
 293          * takes a copy of this number and does not attempt recovery again
 294          * until this number changes.
 295          */
 296         int                             recovery_disabled;
 297
 298         int                             in_sync;        /* know to not need resync */
 299         /* 'open_mutex' avoids races between 'md_open' and 'do_md_stop', so
 300          * that we are never stopping an array while it is open.
 301          * 'reconfig_mutex' protects all other reconfiguration.
 302          * These locks are separate due to conflicting interactions
 303          * with bdev->bd_mutex.
 304          * Lock ordering is:
 305          *  reconfig_mutex -> bd_mutex : e.g. do_md_run -> revalidate_disk
 306          *  bd_mutex -> open_mutex:  e.g. __blkdev_get -> md_open
 307          */
 308         struct mutex                    open_mutex;
 309         struct mutex                    reconfig_mutex;
 310         atomic_t                        active;         /* general refcount */
 311         atomic_t                        openers;        /* number of active opens */
 312
 313         int                             changed;        /* True if we might need to
 314                                                          * reread partition info */
 315         int                             degraded;       /* whether md should consider
 316                                                          * adding a spare
 317                                                          */
 318
 319         atomic_t                        recovery_active; /* blocks scheduled, but not written */
 320         wait_queue_head_t               recovery_wait;
 321         sector_t                        recovery_cp;
 322         sector_t                        resync_min;     /* user requested sync
 323                                                          * starts here */
 324         sector_t                        resync_max;     /* resync should pause
 325                                                          * when it gets here */
 326
 327         struct sysfs_dirent             *sysfs_state;   /* handle for 'array_state'
 328                                                          * file in sysfs.
 329                                                          */
 330         struct sysfs_dirent             *sysfs_action;  /* handle for 'sync_action' */
 331
 332         struct work_struct del_work;    /* used for delayed sysfs removal */
 333
 334         spinlock_t                      write_lock;
 335         wait_queue_head_t               sb_wait;        /* for waiting on superblock updates */
 336         atomic_t                        pending_writes; /* number of active superblock writes */
 337
 338         unsigned int                    safemode;       /* if set, update "clean" superblock
 339                                                          * when no writes pending.
 340                                                          */
 341         unsigned int                    safemode_delay;
 342         struct timer_list               safemode_timer;
 343         atomic_t                        writes_pending;
 344         struct request_queue            *queue; /* for plugging ... */
 345
 346         struct bitmap                   *bitmap; /* the bitmap for the device */
 347         struct {
 348                 struct file             *file; /* the bitmap file */
 349                 loff_t                  offset; /* offset from superblock of
 350                                                  * start of bitmap. May be
 351                                                  * negative, but not '0'
 352                                                  * For external metadata, offset
 353                                                  * from start of device.
 354                                                  */
 355                 loff_t                  default_offset; /* this is the offset to use when
 356                                                          * hot-adding a bitmap.  It should
 357                                                          * eventually be settable by sysfs.
 358                                                          */
 359                 struct mutex            mutex;
 360                 unsigned long           chunksize;
 361                 unsigned long           daemon_sleep; /* how many jiffies between updates? */
 362                 unsigned long           max_write_behind; /* write-behind mode */
 363                 int                     external;
 364         } bitmap_info;
 365
 366         atomic_t                        max_corr_read_errors; /* max read retries */
 367         struct list_head                all_mddevs;
 368
 369         struct attribute_group          *to_remove;
 370
 371         struct bio_set                  *bio_set;
 372
 373         /* Generic flush handling.
 374          * The last to finish preflush schedules a worker to submit
 375          * the rest of the request (without the REQ_FLUSH flag).
 376          */
 377         struct bio *flush_bio;
 378         atomic_t flush_pending;
 379         struct work_struct flush_work;
 380         struct work_struct event_work;  /* used by dm to report failure event */
 381         void (*sync_super)(mddev_t *mddev, mdk_rdev_t *rdev);
 382 };
 383
 384
 385 static inline void rdev_dec_pending(mdk_rdev_t *rdev, mddev_t *mddev)
 386 {
 387         int faulty = test_bit(Faulty, &rdev->flags);
 388         if (atomic_dec_and_test(&rdev->nr_pending) && faulty)
 389                 set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
 390 }
 391
 392 static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
 393 {
 394         atomic_add(nr_sectors, &bdev->bd_contains->bd_disk->sync_io);
 395 }
 396
 397 struct mdk_personality
 398 {
 399         char *name;
 400         int level;
 401         struct list_head list;
 402         struct module *owner;
 403         int (*make_request)(mddev_t *mddev, struct bio *bio);
 404         int (*run)(mddev_t *mddev);
 405         int (*stop)(mddev_t *mddev);
 406         void (*status)(struct seq_file *seq, mddev_t *mddev);
 407         /* error_handler must set ->faulty and clear ->in_sync
 408          * if appropriate, and should abort recovery if needed
 409          */
 410         void (*error_handler)(mddev_t *mddev, mdk_rdev_t *rdev);
 411         int (*hot_add_disk) (mddev_t *mddev, mdk_rdev_t *rdev);
 412         int (*hot_remove_disk) (mddev_t *mddev, int number);
 413         int (*spare_active) (mddev_t *mddev);
 414         sector_t (*sync_request)(mddev_t *mddev, sector_t sector_nr, int *skipped, int go_faster);
 415         int (*resize) (mddev_t *mddev, sector_t sectors);
 416         sector_t (*size) (mddev_t *mddev, sector_t sectors, int raid_disks);
 417         int (*check_reshape) (mddev_t *mddev);
 418         int (*start_reshape) (mddev_t *mddev);
 419         void (*finish_reshape) (mddev_t *mddev);
 420         /* quiesce moves between quiescence states
 421          * 0 - fully active
 422          * 1 - no new requests allowed
 423          * others - reserved
 424          */
 425         void (*quiesce) (mddev_t *mddev, int state);
 426         /* takeover is used to transition an array from one
 427          * personality to another.  The new personality must be able
 428          * to handle the data in the current layout.
 429          * e.g. 2drive raid1 -> 2drive raid5
 430          *      ndrive raid5 -> degraded n+1drive raid6 with special layout
 431          * If the takeover succeeds, a new 'private' structure is returned.
 432          * This needs to be installed and then ->run used to activate the
 433          * array.
 434          */
 435         void *(*takeover) (mddev_t *mddev);
 436 };
 437
 438
 439 struct md_sysfs_entry {
 440         struct attribute attr;
 441         ssize_t (*show)(mddev_t *, char *);
 442         ssize_t (*store)(mddev_t *, const char *, size_t);
 443 };
 444 extern struct attribute_group md_bitmap_group;
 445
 446 static inline struct sysfs_dirent *sysfs_get_dirent_safe(struct sysfs_dirent *sd, char *name)
 447 {
 448         if (sd)
 449                 return sysfs_get_dirent(sd, NULL, name);
 450         return sd;
 451 }
 452 static inline void sysfs_notify_dirent_safe(struct sysfs_dirent *sd)
 453 {
 454         if (sd)
 455                 sysfs_notify_dirent(sd);
 456 }
 457
 458 static inline char * mdname (mddev_t * mddev)
 459 {
 460         return mddev->gendisk ? mddev->gendisk->disk_name : "mdX";
 461 }
 462
 463 static inline int sysfs_link_rdev(mddev_t *mddev, mdk_rdev_t *rdev)
 464 {
 465         char nm[20];
 466         sprintf(nm, "rd%d", rdev->raid_disk);
 467         return sysfs_create_link(&mddev->kobj, &rdev->kobj, nm);
 468 }
 469
 470 static inline void sysfs_unlink_rdev(mddev_t *mddev, mdk_rdev_t *rdev)
 471 {
 472         char nm[20];
 473         sprintf(nm, "rd%d", rdev->raid_disk);
 474         sysfs_remove_link(&mddev->kobj, nm);
 475 }
 476
 477 /*
 478  * iterates through some rdev ringlist. It's safe to remove the
 479  * current 'rdev'. Dont touch 'tmp' though.
 480  */
 481 #define rdev_for_each_list(rdev, tmp, head)                             \
 482         list_for_each_entry_safe(rdev, tmp, head, same_set)
 483
 484 /*
 485  * iterates through the 'same array disks' ringlist
 486  */
 487 #define rdev_for_each(rdev, tmp, mddev)                         \
 488         list_for_each_entry_safe(rdev, tmp, &((mddev)->disks), same_set)
 489
 490 #define rdev_for_each_rcu(rdev, mddev)                          \
 491         list_for_each_entry_rcu(rdev, &((mddev)->disks), same_set)
 492
 493 typedef struct mdk_thread_s {
 494         void                    (*run) (mddev_t *mddev);
 495         mddev_t                 *mddev;
 496         wait_queue_head_t       wqueue;
 497         unsigned long           flags;
 498         struct task_struct      *tsk;
 499         unsigned long           timeout;
 500 } mdk_thread_t;
 501
 502 #define THREAD_WAKEUP  0
 503
 504 #define __wait_event_lock_irq(wq, condition, lock, cmd)                 \
 505 do {                                                                    \
 506         wait_queue_t __wait;                                            \
 507         init_waitqueue_entry(&__wait, current);                         \
 508                                                                         \
 509         add_wait_queue(&wq, &__wait);                                   \
 510         for (;;) {                                                      \
 511                 set_current_state(TASK_UNINTERRUPTIBLE);                \
 512                 if (condition)                                          \
 513                         break;                                          \
 514                 spin_unlock_irq(&lock);                                 \
 515                 cmd;                                                    \
 516                 schedule();                                             \
 517                 spin_lock_irq(&lock);                                   \
 518         }                                                               \
 519         current->state = TASK_RUNNING;                                  \
 520         remove_wait_queue(&wq, &__wait);                                \
 521 } while (0)
 522
 523 #define wait_event_lock_irq(wq, condition, lock, cmd)                   \
 524 do {                                                                    \
 525         if (condition)                                                  \
 526                 break;                                                  \
 527         __wait_event_lock_irq(wq, condition, lock, cmd);                \
 528 } while (0)
 529
 530 static inline void safe_put_page(struct page *p)
 531 {
 532         if (p) put_page(p);
 533 }
 534
 535 extern int register_md_personality(struct mdk_personality *p);
 536 extern int unregister_md_personality(struct mdk_personality *p);
 537 extern mdk_thread_t * md_register_thread(void (*run) (mddev_t *mddev),
 538                                 mddev_t *mddev, const char *name);
 539 extern void md_unregister_thread(mdk_thread_t *thread);
 540 extern void md_wakeup_thread(mdk_thread_t *thread);
 541 extern void md_check_recovery(mddev_t *mddev);
 542 extern void md_write_start(mddev_t *mddev, struct bio *bi);
 543 extern void md_write_end(mddev_t *mddev);
 544 extern void md_done_sync(mddev_t *mddev, int blocks, int ok);
 545 extern void md_error(mddev_t *mddev, mdk_rdev_t *rdev);
 546
 547 extern int mddev_congested(mddev_t *mddev, int bits);
 548 extern void md_flush_request(mddev_t *mddev, struct bio *bio);
 549 extern void md_super_write(mddev_t *mddev, mdk_rdev_t *rdev,
 550                            sector_t sector, int size, struct page *page);
 551 extern void md_super_wait(mddev_t *mddev);
 552 extern int sync_page_io(mdk_rdev_t *rdev, sector_t sector, int size,
 553                         struct page *page, int rw, bool metadata_op);
 554 extern void md_do_sync(mddev_t *mddev);
 555 extern void md_new_event(mddev_t *mddev);
 556 extern int md_allow_write(mddev_t *mddev);
 557 extern void md_wait_for_blocked_rdev(mdk_rdev_t *rdev, mddev_t *mddev);
 558 extern void md_set_array_sectors(mddev_t *mddev, sector_t array_sectors);
 559 extern int md_check_no_bitmap(mddev_t *mddev);
 560 extern int md_integrity_register(mddev_t *mddev);
 561 extern void md_integrity_add_rdev(mdk_rdev_t *rdev, mddev_t *mddev);
 562 extern int strict_strtoul_scaled(const char *cp, unsigned long *res, int scale);
 563 extern void restore_bitmap_write_access(struct file *file);
 564
 565 extern void mddev_init(mddev_t *mddev);
 566 extern int md_run(mddev_t *mddev);
 567 extern void md_stop(mddev_t *mddev);
 568 extern void md_stop_writes(mddev_t *mddev);
 569 extern int md_rdev_init(mdk_rdev_t *rdev);
 570
 571 extern void mddev_suspend(mddev_t *mddev);
 572 extern void mddev_resume(mddev_t *mddev);
 573 extern struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask,
 574                                    mddev_t *mddev);
 575 extern struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
 576                                    mddev_t *mddev);
 577 extern int mddev_check_plugged(mddev_t *mddev);
 578 extern void md_trim_bio(struct bio *bio, int offset, int size);
 579 #endif /* _MD_MD_H */