/*
     md.h : kernel internal structure of the Linux MD driver
            Copyright (C) 1996-98 Ingo Molnar, Gadi Oxman
  	  
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 2, or (at your option)
     any later version.
     
     You should have received a copy of the GNU General Public License
     (for example /usr/src/linux/COPYING); if not, write to the Free
     Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  
  */
  
  #ifndef _MD_MD_H
  #define _MD_MD_H
  
  #include <linux/blkdev.h>
  #include <linux/kobject.h>
  #include <linux/list.h>
  #include <linux/mm.h>
  #include <linux/mutex.h>
  #include <linux/timer.h>
  #include <linux/wait.h>
  #include <linux/workqueue.h>
  
  #define MaxSector (~(sector_t)0)
  
  /* Bad block numbers are stored sorted in a single page.
   * 64bits is used for each block or extent.
   * 54 bits are sector number, 9 bits are extent size,
   * 1 bit is an 'acknowledged' flag.
   */
  #define MD_MAX_BADBLOCKS	(PAGE_SIZE/8)
  
  /*
   * MD's 'extended' device
   */
  struct md_rdev {
  	struct list_head same_set;	/* RAID devices within the same set */
  
  	sector_t sectors;		/* Device size (in 512bytes sectors) */
  	struct mddev *mddev;		/* RAID array if running */
  	int last_events;		/* IO event timestamp */
  
  	/*
  	 * If meta_bdev is non-NULL, it means that a separate device is
  	 * being used to store the metadata (superblock/bitmap) which
  	 * would otherwise be contained on the same device as the data (bdev).
  	 */
  	struct block_device *meta_bdev;
  	struct block_device *bdev;	/* block device handle */
  
  	struct page	*sb_page, *bb_page;
  	int		sb_loaded;
  	__u64		sb_events;
  	sector_t	data_offset;	/* start of data in array */
  	sector_t	new_data_offset;/* only relevant while reshaping */
  	sector_t 	sb_start;	/* offset of the super block (in 512byte sectors) */
  	int		sb_size;	/* bytes in the superblock */
  	int		preferred_minor;	/* autorun support */
  
  	struct kobject	kobj;
  
  	/* A device can be in one of three states based on two flags:
  	 * Not working:   faulty==1 in_sync==0
  	 * Fully working: faulty==0 in_sync==1
  	 * Working, but not
  	 * in sync with array
  	 *                faulty==0 in_sync==0
  	 *
  	 * It can never have faulty==1, in_sync==1
  	 * This reduces the burden of testing multiple flags in many cases
  	 */
  
  	unsigned long	flags;	/* bit set of 'enum flag_bits' bits. */
  	wait_queue_head_t blocked_wait;
  
  	int desc_nr;			/* descriptor index in the superblock */
  	int raid_disk;			/* role of device in array */
  	int new_raid_disk;		/* role that the device will have in
  					 * the array after a level-change completes.
  					 */
  	int saved_raid_disk;		/* role that device used to have in the
  					 * array and could again if we did a partial
  					 * resync from the bitmap
  					 */
  	sector_t	recovery_offset;/* If this device has been partially
  					 * recovered, this is where we were
  					 * up to.
  					 */
  
  	atomic_t	nr_pending;	/* number of pending requests.
  					 * only maintained for arrays that
  					 * support hot removal
  					 */
  	atomic_t	read_errors;	/* number of consecutive read errors that
  					 * we have tried to ignore.
  					 */
  	struct timespec last_read_error;	/* monotonic time since our
  						 * last read error
  						 */
  	atomic_t	corrected_errors; /* number of corrected read errors,
  					   * for reporting to userspace and storing
  					   * in superblock.
  					   */
  	struct work_struct del_work;	/* used for delayed sysfs removal */
  
  	struct kernfs_node *sysfs_state; /* handle for 'state'
  					   * sysfs entry */
  
  	struct badblocks {
  		int	count;		/* count of bad blocks */
  		int	unacked_exist;	/* there probably are unacknowledged
  					 * bad blocks.  This is only cleared
  					 * when a read discovers none
  					 */
  		int	shift;		/* shift from sectors to block size
  					 * a -ve shift means badblocks are
  					 * disabled.*/
  		u64	*page;		/* badblock list */
  		int	changed;
  		seqlock_t lock;
  
  		sector_t sector;
  		sector_t size;		/* in sectors */
  	} badblocks;
  };
  enum flag_bits {
  	Faulty,			/* device is known to have a fault */
  	In_sync,		/* device is in_sync with rest of array */
  	Bitmap_sync,		/* ..actually, not quite In_sync.  Need a
  				 * bitmap-based recovery to get fully in sync
  				 */
  	Unmerged,		/* device is being added to array and should
  				 * be considerred for bvec_merge_fn but not
  				 * yet for actual IO
  				 */
  	WriteMostly,		/* Avoid reading if at all possible */
  	AutoDetected,		/* added by auto-detect */
  	Blocked,		/* An error occurred but has not yet
  				 * been acknowledged by the metadata
  				 * handler, so don't allow writes
  				 * until it is cleared */
  	WriteErrorSeen,		/* A write error has been seen on this
  				 * device
  				 */
  	FaultRecorded,		/* Intermediate state for clearing
  				 * Blocked.  The Fault is/will-be
  				 * recorded in the metadata, but that
  				 * metadata hasn't been stored safely
  				 * on disk yet.
  				 */
  	BlockedBadBlocks,	/* A writer is blocked because they
  				 * found an unacknowledged bad-block.
  				 * This can safely be cleared at any
  				 * time, and the writer will re-check.
  				 * It may be set at any time, and at
  				 * worst the writer will timeout and
  				 * re-check.  So setting it as
  				 * accurately as possible is good, but
  				 * not absolutely critical.
  				 */
  	WantReplacement,	/* This device is a candidate to be
  				 * hot-replaced, either because it has
  				 * reported some faults, or because
  				 * of explicit request.
  				 */
  	Replacement,		/* This device is a replacement for
  				 * a want_replacement device with same
  				 * raid_disk number.
  				 */
  };
  
  #define BB_LEN_MASK	(0x00000000000001FFULL)
  #define BB_OFFSET_MASK	(0x7FFFFFFFFFFFFE00ULL)
  #define BB_ACK_MASK	(0x8000000000000000ULL)
  #define BB_MAX_LEN	512
  #define BB_OFFSET(x)	(((x) & BB_OFFSET_MASK) >> 9)
  #define BB_LEN(x)	(((x) & BB_LEN_MASK) + 1)
  #define BB_ACK(x)	(!!((x) & BB_ACK_MASK))
  #define BB_MAKE(a, l, ack) (((a)<<9) | ((l)-1) | ((u64)(!!(ack)) << 63))
  
  extern int md_is_badblock(struct badblocks *bb, sector_t s, int sectors,
  			  sector_t *first_bad, int *bad_sectors);
  static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
  			      sector_t *first_bad, int *bad_sectors)
  {
  	if (unlikely(rdev->badblocks.count)) {
  		int rv = md_is_badblock(&rdev->badblocks, rdev->data_offset + s,
  					sectors,
  					first_bad, bad_sectors);
  		if (rv)
  			*first_bad -= rdev->data_offset;
  		return rv;
  	}
  	return 0;
  }
  extern int rdev_set_badblocks(struct md_rdev *rdev, sector_t s, int sectors,
  			      int is_new);
  extern int rdev_clear_badblocks(struct md_rdev *rdev, sector_t s, int sectors,
  				int is_new);
  extern void md_ack_all_badblocks(struct badblocks *bb);
  
  struct mddev {
  	void				*private;
  	struct md_personality		*pers;
  	dev_t				unit;
  	int				md_minor;
  	struct list_head		disks;
  	unsigned long			flags;
  #define MD_CHANGE_DEVS	0	/* Some device status has changed */
  #define MD_CHANGE_CLEAN 1	/* transition to or from 'clean' */
  #define MD_CHANGE_PENDING 2	/* switch from 'clean' to 'active' in progress */
  #define MD_UPDATE_SB_FLAGS (1 | 2 | 4)	/* If these are set, md_update_sb needed */
  #define MD_ARRAY_FIRST_USE 3    /* First use of array, needs initialization */
  #define MD_STILL_CLOSED	4	/* If set, then array has not been opened since
  				 * md_ioctl checked on it.
  				 */
  
  	int				suspended;
  	atomic_t			active_io;
  	int				ro;
  	int				sysfs_active; /* set when sysfs deletes
  						       * are happening, so run/
  						       * takeover/stop are not safe
  						       */
  	int				ready; /* See when safe to pass
  						* IO requests down */
  	struct gendisk			*gendisk;
  
  	struct kobject			kobj;
  	int				hold_active;
  #define	UNTIL_IOCTL	1
  #define	UNTIL_STOP	2
  
  	/* Superblock information */
  	int				major_version,
  					minor_version,
  					patch_version;
  	int				persistent;
  	int 				external;	/* metadata is
  							 * managed externally */
  	char				metadata_type[17]; /* externally set*/
  	int				chunk_sectors;
  	time_t				ctime, utime;
  	int				level, layout;
  	char				clevel[16];
  	int				raid_disks;
  	int				max_disks;
  	sector_t			dev_sectors; 	/* used size of
  							 * component devices */
  	sector_t			array_sectors; /* exported array size */
  	int				external_size; /* size managed
  							* externally */
  	__u64				events;
  	/* If the last 'event' was simply a clean->dirty transition, and
  	 * we didn't write it to the spares, then it is safe and simple
  	 * to just decrement the event count on a dirty->clean transition.
  	 * So we record that possibility here.
  	 */
  	int				can_decrease_events;
  
  	char				uuid[16];
  
  	/* If the array is being reshaped, we need to record the
  	 * new shape and an indication of where we are up to.
  	 * This is written to the superblock.
  	 * If reshape_position is MaxSector, then no reshape is happening (yet).
  	 */
  	sector_t			reshape_position;
  	int				delta_disks, new_level, new_layout;
  	int				new_chunk_sectors;
  	int				reshape_backwards;
  
  	struct md_thread		*thread;	/* management thread */
  	struct md_thread		*sync_thread;	/* doing resync or reconstruct */
  
  	/* 'last_sync_action' is initialized to "none".  It is set when a
  	 * sync operation (i.e "data-check", "requested-resync", "resync",
  	 * "recovery", or "reshape") is started.  It holds this value even
  	 * when the sync thread is "frozen" (interrupted) or "idle" (stopped
  	 * or finished).  It is overwritten when a new sync operation is begun.
  	 */
  	char				*last_sync_action;
  	sector_t			curr_resync;	/* last block scheduled */
  	/* As resync requests can complete out of order, we cannot easily track
  	 * how much resync has been completed.  So we occasionally pause until
  	 * everything completes, then set curr_resync_completed to curr_resync.
  	 * As such it may be well behind the real resync mark, but it is a value
  	 * we are certain of.
  	 */
  	sector_t			curr_resync_completed;
  	unsigned long			resync_mark;	/* a recent timestamp */
  	sector_t			resync_mark_cnt;/* blocks written at resync_mark */
  	sector_t			curr_mark_cnt; /* blocks scheduled now */
  
  	sector_t			resync_max_sectors; /* may be set by personality */
  
  	atomic64_t			resync_mismatches; /* count of sectors where
  							    * parity/replica mismatch found
  							    */
  
  	/* allow user-space to request suspension of IO to regions of the array */
  	sector_t			suspend_lo;
  	sector_t			suspend_hi;
  	/* if zero, use the system-wide default */
  	int				sync_speed_min;
  	int				sync_speed_max;
  
  	/* resync even though the same disks are shared among md-devices */
  	int				parallel_resync;
  
  	int				ok_start_degraded;
  	/* recovery/resync flags 
  	 * NEEDED:   we might need to start a resync/recover
  	 * RUNNING:  a thread is running, or about to be started
  	 * SYNC:     actually doing a resync, not a recovery
  	 * RECOVER:  doing recovery, or need to try it.
  	 * INTR:     resync needs to be aborted for some reason
  	 * DONE:     thread is done and is waiting to be reaped
  	 * REQUEST:  user-space has requested a sync (used with SYNC)
  	 * CHECK:    user-space request for check-only, no repair
  	 * RESHAPE:  A reshape is happening
  	 * ERROR:    sync-action interrupted because io-error
  	 *
  	 * If neither SYNC or RESHAPE are set, then it is a recovery.
  	 */
  #define	MD_RECOVERY_RUNNING	0
  #define	MD_RECOVERY_SYNC	1
  #define	MD_RECOVERY_RECOVER	2
  #define	MD_RECOVERY_INTR	3
  #define	MD_RECOVERY_DONE	4
  #define	MD_RECOVERY_NEEDED	5
  #define	MD_RECOVERY_REQUESTED	6
  #define	MD_RECOVERY_CHECK	7
  #define MD_RECOVERY_RESHAPE	8
  #define	MD_RECOVERY_FROZEN	9
  #define	MD_RECOVERY_ERROR	10
  
  	unsigned long			recovery;
  	/* If a RAID personality determines that recovery (of a particular
  	 * device) will fail due to a read error on the source device, it
  	 * takes a copy of this number and does not attempt recovery again
  	 * until this number changes.
  	 */
  	int				recovery_disabled;
  
  	int				in_sync;	/* know to not need resync */
  	/* 'open_mutex' avoids races between 'md_open' and 'do_md_stop', so
  	 * that we are never stopping an array while it is open.
  	 * 'reconfig_mutex' protects all other reconfiguration.
  	 * These locks are separate due to conflicting interactions
  	 * with bdev->bd_mutex.
  	 * Lock ordering is:
  	 *  reconfig_mutex -> bd_mutex : e.g. do_md_run -> revalidate_disk
  	 *  bd_mutex -> open_mutex:  e.g. __blkdev_get -> md_open
  	 */
  	struct mutex			open_mutex;
  	struct mutex			reconfig_mutex;
  	atomic_t			active;		/* general refcount */
  	atomic_t			openers;	/* number of active opens */
  
  	int				changed;	/* True if we might need to
  							 * reread partition info */
  	int				degraded;	/* whether md should consider
  							 * adding a spare
  							 */
  	int				merge_check_needed; /* at least one
  							     * member device
  							     * has a
  							     * merge_bvec_fn */
  
  	atomic_t			recovery_active; /* blocks scheduled, but not written */
  	wait_queue_head_t		recovery_wait;
  	sector_t			recovery_cp;
  	sector_t			resync_min;	/* user requested sync
  							 * starts here */
  	sector_t			resync_max;	/* resync should pause
  							 * when it gets here */
  
  	struct kernfs_node		*sysfs_state;	/* handle for 'array_state'
  							 * file in sysfs.
  							 */
  	struct kernfs_node		*sysfs_action;  /* handle for 'sync_action' */
  
  	struct work_struct del_work;	/* used for delayed sysfs removal */
  
  	spinlock_t			write_lock;
  	wait_queue_head_t		sb_wait;	/* for waiting on superblock updates */
  	atomic_t			pending_writes;	/* number of active superblock writes */
  
  	unsigned int			safemode;	/* if set, update "clean" superblock
  							 * when no writes pending.
  							 */ 
  	unsigned int			safemode_delay;
  	struct timer_list		safemode_timer;
  	atomic_t			writes_pending; 
  	struct request_queue		*queue;	/* for plugging ... */
  
  	struct bitmap                   *bitmap; /* the bitmap for the device */
  	struct {
  		struct file		*file; /* the bitmap file */
  		loff_t			offset; /* offset from superblock of
  						 * start of bitmap. May be
  						 * negative, but not '0'
  						 * For external metadata, offset
  						 * from start of device. 
  						 */
  		unsigned long		space; /* space available at this offset */
  		loff_t			default_offset; /* this is the offset to use when
  							 * hot-adding a bitmap.  It should
  							 * eventually be settable by sysfs.
  							 */
  		unsigned long		default_space; /* space available at
  							* default offset */
  		struct mutex		mutex;
  		unsigned long		chunksize;
  		unsigned long		daemon_sleep; /* how many jiffies between updates? */
  		unsigned long		max_write_behind; /* write-behind mode */
  		int			external;
  	} bitmap_info;
  
  	atomic_t 			max_corr_read_errors; /* max read retries */
  	struct list_head		all_mddevs;
  
  	struct attribute_group		*to_remove;
  
  	struct bio_set			*bio_set;
  
  	/* Generic flush handling.
  	 * The last to finish preflush schedules a worker to submit
  	 * the rest of the request (without the REQ_FLUSH flag).
  	 */
  	struct bio *flush_bio;
  	atomic_t flush_pending;
  	struct work_struct flush_work;
  	struct work_struct event_work;	/* used by dm to report failure event */
  	void (*sync_super)(struct mddev *mddev, struct md_rdev *rdev);
  };
  
  
  static inline void rdev_dec_pending(struct md_rdev *rdev, struct mddev *mddev)
  {
  	int faulty = test_bit(Faulty, &rdev->flags);
  	if (atomic_dec_and_test(&rdev->nr_pending) && faulty)
  		set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
  }
  
  static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sectors)
  {
          atomic_add(nr_sectors, &bdev->bd_contains->bd_disk->sync_io);
  }
  
  struct md_personality
  {
  	char *name;
  	int level;
  	struct list_head list;
  	struct module *owner;
  	void (*make_request)(struct mddev *mddev, struct bio *bio);
  	int (*run)(struct mddev *mddev);
  	int (*stop)(struct mddev *mddev);
  	void (*status)(struct seq_file *seq, struct mddev *mddev);
  	/* error_handler must set ->faulty and clear ->in_sync
  	 * if appropriate, and should abort recovery if needed 
  	 */
  	void (*error_handler)(struct mddev *mddev, struct md_rdev *rdev);
  	int (*hot_add_disk) (struct mddev *mddev, struct md_rdev *rdev);
  	int (*hot_remove_disk) (struct mddev *mddev, struct md_rdev *rdev);
  	int (*spare_active) (struct mddev *mddev);
  	sector_t (*sync_request)(struct mddev *mddev, sector_t sector_nr, int *skipped, int go_faster);
  	int (*resize) (struct mddev *mddev, sector_t sectors);
  	sector_t (*size) (struct mddev *mddev, sector_t sectors, int raid_disks);
  	int (*check_reshape) (struct mddev *mddev);
  	int (*start_reshape) (struct mddev *mddev);
  	void (*finish_reshape) (struct mddev *mddev);
  	/* quiesce moves between quiescence states
  	 * 0 - fully active
  	 * 1 - no new requests allowed
  	 * others - reserved
  	 */
  	void (*quiesce) (struct mddev *mddev, int state);
  	/* takeover is used to transition an array from one
  	 * personality to another.  The new personality must be able
  	 * to handle the data in the current layout.
  	 * e.g. 2drive raid1 -> 2drive raid5
  	 *      ndrive raid5 -> degraded n+1drive raid6 with special layout
  	 * If the takeover succeeds, a new 'private' structure is returned.
  	 * This needs to be installed and then ->run used to activate the
  	 * array.
  	 */
  	void *(*takeover) (struct mddev *mddev);
  };
  
  
  struct md_sysfs_entry {
  	struct attribute attr;
  	ssize_t (*show)(struct mddev *, char *);
  	ssize_t (*store)(struct mddev *, const char *, size_t);
  };
  extern struct attribute_group md_bitmap_group;
  
  static inline struct kernfs_node *sysfs_get_dirent_safe(struct kernfs_node *sd, char *name)
  {
  	if (sd)
  		return sysfs_get_dirent(sd, name);
  	return sd;
  }
  static inline void sysfs_notify_dirent_safe(struct kernfs_node *sd)
  {
  	if (sd)
  		sysfs_notify_dirent(sd);
  }
  
  static inline char * mdname (struct mddev * mddev)
  {
  	return mddev->gendisk ? mddev->gendisk->disk_name : "mdX";
  }
  
  static inline int sysfs_link_rdev(struct mddev *mddev, struct md_rdev *rdev)
  {
  	char nm[20];
  	if (!test_bit(Replacement, &rdev->flags) && mddev->kobj.sd) {
  		sprintf(nm, "rd%d", rdev->raid_disk);
  		return sysfs_create_link(&mddev->kobj, &rdev->kobj, nm);
  	} else
  		return 0;
  }
  
  static inline void sysfs_unlink_rdev(struct mddev *mddev, struct md_rdev *rdev)
  {
  	char nm[20];
  	if (!test_bit(Replacement, &rdev->flags) && mddev->kobj.sd) {
  		sprintf(nm, "rd%d", rdev->raid_disk);
  		sysfs_remove_link(&mddev->kobj, nm);
  	}
  }
  
  /*
   * iterates through some rdev ringlist. It's safe to remove the
   * current 'rdev'. Dont touch 'tmp' though.
   */
  #define rdev_for_each_list(rdev, tmp, head)				\
  	list_for_each_entry_safe(rdev, tmp, head, same_set)
  
  /*
   * iterates through the 'same array disks' ringlist
   */
  #define rdev_for_each(rdev, mddev)				\
  	list_for_each_entry(rdev, &((mddev)->disks), same_set)
  
  #define rdev_for_each_safe(rdev, tmp, mddev)				\
  	list_for_each_entry_safe(rdev, tmp, &((mddev)->disks), same_set)
  
  #define rdev_for_each_rcu(rdev, mddev)				\
  	list_for_each_entry_rcu(rdev, &((mddev)->disks), same_set)
  
  struct md_thread {
  	void			(*run) (struct md_thread *thread);
  	struct mddev		*mddev;
  	wait_queue_head_t	wqueue;
  	unsigned long           flags;
  	struct task_struct	*tsk;
  	unsigned long		timeout;
  	void			*private;
  };
  
  #define THREAD_WAKEUP  0
  
  static inline void safe_put_page(struct page *p)
  {
  	if (p) put_page(p);
  }
  
  extern int register_md_personality(struct md_personality *p);
  extern int unregister_md_personality(struct md_personality *p);
  extern struct md_thread *md_register_thread(
  	void (*run)(struct md_thread *thread),
  	struct mddev *mddev,
  	const char *name);
  extern void md_unregister_thread(struct md_thread **threadp);
  extern void md_wakeup_thread(struct md_thread *thread);
  extern void md_check_recovery(struct mddev *mddev);
  extern void md_reap_sync_thread(struct mddev *mddev);
  extern void md_write_start(struct mddev *mddev, struct bio *bi);
  extern void md_write_end(struct mddev *mddev);
  extern void md_done_sync(struct mddev *mddev, int blocks, int ok);
  extern void md_error(struct mddev *mddev, struct md_rdev *rdev);
  extern void md_finish_reshape(struct mddev *mddev);
  
  extern int mddev_congested(struct mddev *mddev, int bits);
  extern void md_flush_request(struct mddev *mddev, struct bio *bio);
  extern void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
  			   sector_t sector, int size, struct page *page);
  extern void md_super_wait(struct mddev *mddev);
  extern int sync_page_io(struct md_rdev *rdev, sector_t sector, int size, 
  			struct page *page, int rw, bool metadata_op);
  extern void md_do_sync(struct md_thread *thread);
  extern void md_new_event(struct mddev *mddev);
  extern int md_allow_write(struct mddev *mddev);
  extern void md_wait_for_blocked_rdev(struct md_rdev *rdev, struct mddev *mddev);
  extern void md_set_array_sectors(struct mddev *mddev, sector_t array_sectors);
  extern int md_check_no_bitmap(struct mddev *mddev);
  extern int md_integrity_register(struct mddev *mddev);
  extern void md_integrity_add_rdev(struct md_rdev *rdev, struct mddev *mddev);
  extern int strict_strtoul_scaled(const char *cp, unsigned long *res, int scale);
  extern void restore_bitmap_write_access(struct file *file);
  
  extern void mddev_init(struct mddev *mddev);
  extern int md_run(struct mddev *mddev);
  extern void md_stop(struct mddev *mddev);
  extern void md_stop_writes(struct mddev *mddev);
  extern int md_rdev_init(struct md_rdev *rdev);
  extern void md_rdev_clear(struct md_rdev *rdev);
  
  extern void mddev_suspend(struct mddev *mddev);
  extern void mddev_resume(struct mddev *mddev);
  extern struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask,
  				   struct mddev *mddev);
  extern struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
  				   struct mddev *mddev);
  
  extern void md_unplug(struct blk_plug_cb *cb, bool from_schedule);
  static inline int mddev_check_plugged(struct mddev *mddev)
  {
  	return !!blk_check_plugged(md_unplug, mddev,
  				   sizeof(struct blk_plug_cb));
  }
  #endif /* _MD_MD_H */