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Commit 2230dfe4 authored by NeilBrown's avatar NeilBrown
Browse files

md: beginnings of bad block management. 



This the first step in allowing md to track bad-blocks per-device so
that we can fail individual blocks rather than the whole device.

This patch just adds a data structure for recording bad blocks, with
routines to add, remove, search the list.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Reviewed-by: default avatarNamhyung Kim <namhyung@gmail.com>
parent a519b26d

drivers/md/md.c

+412 −3
Original line number Diff line number Diff line
@@ -1952,6 +1952,9 @@ static void unbind_rdev_from_array(mdk_rdev_t * rdev) 
	sysfs_remove_link(&rdev->kobj, "block");

	sysfs_put(rdev->sysfs_state);

	rdev->sysfs_state = NULL;

	kfree(rdev->badblocks.page);

	rdev->badblocks.count = 0;

	rdev->badblocks.page = NULL;

	/* We need to delay this, otherwise we can deadlock when

	 * writing to 'remove' to "dev/state".  We also need

	 * to delay it due to rcu usage.
@@ -2778,7 +2781,7 @@ static struct kobj_type rdev_ktype = { 
	.default_attrs	= rdev_default_attrs,

};



void md_rdev_init(mdk_rdev_t *rdev)

int md_rdev_init(mdk_rdev_t *rdev)

{

	rdev->desc_nr = -1;

	rdev->saved_raid_disk = -1;
@@ -2794,6 +2797,19 @@ void md_rdev_init(mdk_rdev_t *rdev) 


	INIT_LIST_HEAD(&rdev->same_set);

	init_waitqueue_head(&rdev->blocked_wait);



	/* Add space to store bad block list.

	 * This reserves the space even on arrays where it cannot

	 * be used - I wonder if that matters

	 */

	rdev->badblocks.count = 0;

	rdev->badblocks.shift = 0;

	rdev->badblocks.page = kmalloc(PAGE_SIZE, GFP_KERNEL);

	seqlock_init(&rdev->badblocks.lock);

	if (rdev->badblocks.page == NULL)

		return -ENOMEM;



	return 0;

}

EXPORT_SYMBOL_GPL(md_rdev_init);

/*
@@ -2819,8 +2835,11 @@ static mdk_rdev_t *md_import_device(dev_t newdev, int super_format, int super_mi 
		return ERR_PTR(-ENOMEM);

	}



	md_rdev_init(rdev);

	if ((err = alloc_disk_sb(rdev)))

	err = md_rdev_init(rdev);

	if (err)

		goto abort_free;

	err = alloc_disk_sb(rdev);

	if (err)

		goto abort_free;



	err = lock_rdev(rdev, newdev, super_format == -2);
@@ -2865,6 +2884,7 @@ abort_free: 
			unlock_rdev(rdev);

		free_disk_sb(rdev);

	}

	kfree(rdev->badblocks.page);

	kfree(rdev);

	return ERR_PTR(err);

}
@@ -7327,6 +7347,395 @@ void md_wait_for_blocked_rdev(mdk_rdev_t *rdev, mddev_t *mddev) 
}

EXPORT_SYMBOL(md_wait_for_blocked_rdev);





/* Bad block management.

 * We can record which blocks on each device are 'bad' and so just

 * fail those blocks, or that stripe, rather than the whole device.

 * Entries in the bad-block table are 64bits wide.  This comprises:

 * Length of bad-range, in sectors: 0-511 for lengths 1-512

 * Start of bad-range, sector offset, 54 bits (allows 8 exbibytes)

 *  A 'shift' can be set so that larger blocks are tracked and

 *  consequently larger devices can be covered.

 * 'Acknowledged' flag - 1 bit. - the most significant bit.

 *

 * Locking of the bad-block table uses a seqlock so md_is_badblock

 * might need to retry if it is very unlucky.

 * We will sometimes want to check for bad blocks in a bi_end_io function,

 * so we use the write_seqlock_irq variant.

 *

 * When looking for a bad block we specify a range and want to

 * know if any block in the range is bad.  So we binary-search

 * to the last range that starts at-or-before the given endpoint,

 * (or "before the sector after the target range")

 * then see if it ends after the given start.

 * We return

 *  0 if there are no known bad blocks in the range

 *  1 if there are known bad block which are all acknowledged

 * -1 if there are bad blocks which have not yet been acknowledged in metadata.

 * plus the start/length of the first bad section we overlap.

 */

int md_is_badblock(struct badblocks *bb, sector_t s, int sectors,

		   sector_t *first_bad, int *bad_sectors)

{

	int hi;

	int lo = 0;

	u64 *p = bb->page;

	int rv = 0;

	sector_t target = s + sectors;

	unsigned seq;



	if (bb->shift > 0) {

		/* round the start down, and the end up */

		s >>= bb->shift;

		target += (1<<bb->shift) - 1;

		target >>= bb->shift;

		sectors = target - s;

	}

	/* 'target' is now the first block after the bad range */



retry:

	seq = read_seqbegin(&bb->lock);



	hi = bb->count;



	/* Binary search between lo and hi for 'target'

	 * i.e. for the last range that starts before 'target'

	 */

	/* INVARIANT: ranges before 'lo' and at-or-after 'hi'

	 * are known not to be the last range before target.

	 * VARIANT: hi-lo is the number of possible

	 * ranges, and decreases until it reaches 1

	 */

	while (hi - lo > 1) {

		int mid = (lo + hi) / 2;

		sector_t a = BB_OFFSET(p[mid]);

		if (a < target)

			/* This could still be the one, earlier ranges

			 * could not. */

			lo = mid;

		else

			/* This and later ranges are definitely out. */

			hi = mid;

	}

	/* 'lo' might be the last that started before target, but 'hi' isn't */

	if (hi > lo) {

		/* need to check all range that end after 's' to see if

		 * any are unacknowledged.

		 */

		while (lo >= 0 &&

		       BB_OFFSET(p[lo]) + BB_LEN(p[lo]) > s) {

			if (BB_OFFSET(p[lo]) < target) {

				/* starts before the end, and finishes after

				 * the start, so they must overlap

				 */

				if (rv != -1 && BB_ACK(p[lo]))

					rv = 1;

				else

					rv = -1;

				*first_bad = BB_OFFSET(p[lo]);

				*bad_sectors = BB_LEN(p[lo]);

			}

			lo--;

		}

	}



	if (read_seqretry(&bb->lock, seq))

		goto retry;



	return rv;

}

EXPORT_SYMBOL_GPL(md_is_badblock);



/*

 * Add a range of bad blocks to the table.

 * This might extend the table, or might contract it

 * if two adjacent ranges can be merged.

 * We binary-search to find the 'insertion' point, then

 * decide how best to handle it.

 */

static int md_set_badblocks(struct badblocks *bb, sector_t s, int sectors,

			    int acknowledged)

{

	u64 *p;

	int lo, hi;

	int rv = 1;



	if (bb->shift < 0)

		/* badblocks are disabled */

		return 0;



	if (bb->shift) {

		/* round the start down, and the end up */

		sector_t next = s + sectors;

		s >>= bb->shift;

		next += (1<<bb->shift) - 1;

		next >>= bb->shift;

		sectors = next - s;

	}



	write_seqlock_irq(&bb->lock);



	p = bb->page;

	lo = 0;

	hi = bb->count;

	/* Find the last range that starts at-or-before 's' */

	while (hi - lo > 1) {

		int mid = (lo + hi) / 2;

		sector_t a = BB_OFFSET(p[mid]);

		if (a <= s)

			lo = mid;

		else

			hi = mid;

	}

	if (hi > lo && BB_OFFSET(p[lo]) > s)

		hi = lo;



	if (hi > lo) {

		/* we found a range that might merge with the start

		 * of our new range

		 */

		sector_t a = BB_OFFSET(p[lo]);

		sector_t e = a + BB_LEN(p[lo]);

		int ack = BB_ACK(p[lo]);

		if (e >= s) {

			/* Yes, we can merge with a previous range */

			if (s == a && s + sectors >= e)

				/* new range covers old */

				ack = acknowledged;

			else

				ack = ack && acknowledged;



			if (e < s + sectors)

				e = s + sectors;

			if (e - a <= BB_MAX_LEN) {

				p[lo] = BB_MAKE(a, e-a, ack);

				s = e;

			} else {

				/* does not all fit in one range,

				 * make p[lo] maximal

				 */

				if (BB_LEN(p[lo]) != BB_MAX_LEN)

					p[lo] = BB_MAKE(a, BB_MAX_LEN, ack);

				s = a + BB_MAX_LEN;

			}

			sectors = e - s;

		}

	}

	if (sectors && hi < bb->count) {

		/* 'hi' points to the first range that starts after 's'.

		 * Maybe we can merge with the start of that range */

		sector_t a = BB_OFFSET(p[hi]);

		sector_t e = a + BB_LEN(p[hi]);

		int ack = BB_ACK(p[hi]);

		if (a <= s + sectors) {

			/* merging is possible */

			if (e <= s + sectors) {

				/* full overlap */

				e = s + sectors;

				ack = acknowledged;

			} else

				ack = ack && acknowledged;



			a = s;

			if (e - a <= BB_MAX_LEN) {

				p[hi] = BB_MAKE(a, e-a, ack);

				s = e;

			} else {

				p[hi] = BB_MAKE(a, BB_MAX_LEN, ack);

				s = a + BB_MAX_LEN;

			}

			sectors = e - s;

			lo = hi;

			hi++;

		}

	}

	if (sectors == 0 && hi < bb->count) {

		/* we might be able to combine lo and hi */

		/* Note: 's' is at the end of 'lo' */

		sector_t a = BB_OFFSET(p[hi]);

		int lolen = BB_LEN(p[lo]);

		int hilen = BB_LEN(p[hi]);

		int newlen = lolen + hilen - (s - a);

		if (s >= a && newlen < BB_MAX_LEN) {

			/* yes, we can combine them */

			int ack = BB_ACK(p[lo]) && BB_ACK(p[hi]);

			p[lo] = BB_MAKE(BB_OFFSET(p[lo]), newlen, ack);

			memmove(p + hi, p + hi + 1,

				(bb->count - hi - 1) * 8);

			bb->count--;

		}

	}

	while (sectors) {

		/* didn't merge (it all).

		 * Need to add a range just before 'hi' */

		if (bb->count >= MD_MAX_BADBLOCKS) {

			/* No room for more */

			rv = 0;

			break;

		} else {

			int this_sectors = sectors;

			memmove(p + hi + 1, p + hi,

				(bb->count - hi) * 8);

			bb->count++;



			if (this_sectors > BB_MAX_LEN)

				this_sectors = BB_MAX_LEN;

			p[hi] = BB_MAKE(s, this_sectors, acknowledged);

			sectors -= this_sectors;

			s += this_sectors;

		}

	}



	bb->changed = 1;

	write_sequnlock_irq(&bb->lock);



	return rv;

}



int rdev_set_badblocks(mdk_rdev_t *rdev, sector_t s, int sectors,

		       int acknowledged)

{

	int rv = md_set_badblocks(&rdev->badblocks,

				  s + rdev->data_offset, sectors, acknowledged);

	if (rv) {

		/* Make sure they get written out promptly */

		set_bit(MD_CHANGE_CLEAN, &rdev->mddev->flags);

		md_wakeup_thread(rdev->mddev->thread);

	}

	return rv;

}

EXPORT_SYMBOL_GPL(rdev_set_badblocks);



/*

 * Remove a range of bad blocks from the table.

 * This may involve extending the table if we spilt a region,

 * but it must not fail.  So if the table becomes full, we just

 * drop the remove request.

 */

static int md_clear_badblocks(struct badblocks *bb, sector_t s, int sectors)

{

	u64 *p;

	int lo, hi;

	sector_t target = s + sectors;

	int rv = 0;



	if (bb->shift > 0) {

		/* When clearing we round the start up and the end down.

		 * This should not matter as the shift should align with

		 * the block size and no rounding should ever be needed.

		 * However it is better the think a block is bad when it

		 * isn't than to think a block is not bad when it is.

		 */

		s += (1<<bb->shift) - 1;

		s >>= bb->shift;

		target >>= bb->shift;

		sectors = target - s;

	}



	write_seqlock_irq(&bb->lock);



	p = bb->page;

	lo = 0;

	hi = bb->count;

	/* Find the last range that starts before 'target' */

	while (hi - lo > 1) {

		int mid = (lo + hi) / 2;

		sector_t a = BB_OFFSET(p[mid]);

		if (a < target)

			lo = mid;

		else

			hi = mid;

	}

	if (hi > lo) {

		/* p[lo] is the last range that could overlap the

		 * current range.  Earlier ranges could also overlap,

		 * but only this one can overlap the end of the range.

		 */

		if (BB_OFFSET(p[lo]) + BB_LEN(p[lo]) > target) {

			/* Partial overlap, leave the tail of this range */

			int ack = BB_ACK(p[lo]);

			sector_t a = BB_OFFSET(p[lo]);

			sector_t end = a + BB_LEN(p[lo]);



			if (a < s) {

				/* we need to split this range */

				if (bb->count >= MD_MAX_BADBLOCKS) {

					rv = 0;

					goto out;

				}

				memmove(p+lo+1, p+lo, (bb->count - lo) * 8);

				bb->count++;

				p[lo] = BB_MAKE(a, s-a, ack);

				lo++;

			}

			p[lo] = BB_MAKE(target, end - target, ack);

			/* there is no longer an overlap */

			hi = lo;

			lo--;

		}

		while (lo >= 0 &&

		       BB_OFFSET(p[lo]) + BB_LEN(p[lo]) > s) {

			/* This range does overlap */

			if (BB_OFFSET(p[lo]) < s) {

				/* Keep the early parts of this range. */

				int ack = BB_ACK(p[lo]);

				sector_t start = BB_OFFSET(p[lo]);

				p[lo] = BB_MAKE(start, s - start, ack);

				/* now low doesn't overlap, so.. */

				break;

			}

			lo--;

		}

		/* 'lo' is strictly before, 'hi' is strictly after,

		 * anything between needs to be discarded

		 */

		if (hi - lo > 1) {

			memmove(p+lo+1, p+hi, (bb->count - hi) * 8);

			bb->count -= (hi - lo - 1);

		}

	}



	bb->changed = 1;

out:

	write_sequnlock_irq(&bb->lock);

	return rv;

}



int rdev_clear_badblocks(mdk_rdev_t *rdev, sector_t s, int sectors)

{

	return md_clear_badblocks(&rdev->badblocks,

				  s + rdev->data_offset,

				  sectors);

}

EXPORT_SYMBOL_GPL(rdev_clear_badblocks);



/*

 * Acknowledge all bad blocks in a list.

 * This only succeeds if ->changed is clear.  It is used by

 * in-kernel metadata updates

 */

void md_ack_all_badblocks(struct badblocks *bb)

{

	if (bb->page == NULL || bb->changed)

		/* no point even trying */

		return;

	write_seqlock_irq(&bb->lock);



	if (bb->changed == 0) {

		u64 *p = bb->page;

		int i;

		for (i = 0; i < bb->count ; i++) {

			if (!BB_ACK(p[i])) {

				sector_t start = BB_OFFSET(p[i]);

				int len = BB_LEN(p[i]);

				p[i] = BB_MAKE(start, len, 1);

			}

		}

	}

	write_sequnlock_irq(&bb->lock);

}

EXPORT_SYMBOL_GPL(md_ack_all_badblocks);



static int md_notify_reboot(struct notifier_block *this,

			    unsigned long code, void *x)

{

drivers/md/md.h

+47 −1
Original line number Diff line number Diff line
@@ -29,6 +29,13 @@ 
typedef struct mddev_s mddev_t;

typedef struct mdk_rdev_s mdk_rdev_t;



/* 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

 */
@@ -111,8 +118,47 @@ struct mdk_rdev_s 


	struct sysfs_dirent *sysfs_state; /* handle for 'state'

					   * sysfs entry */



	struct badblocks {

		int	count;		/* count of bad blocks */

		int	shift;		/* shift from sectors to block size

					 * a -ve shift means badblocks are

					 * disabled.*/

		u64	*page;		/* badblock list */

		int	changed;

		seqlock_t lock;

	} badblocks;

};



#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(mdk_rdev_t *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(mdk_rdev_t *rdev, sector_t s, int sectors,

			      int acknowledged);

extern int rdev_clear_badblocks(mdk_rdev_t *rdev, sector_t s, int sectors);

extern void md_ack_all_badblocks(struct badblocks *bb);



struct mddev_s

{

	void				*private;
@@ -517,7 +563,7 @@ extern void mddev_init(mddev_t *mddev); 
extern int md_run(mddev_t *mddev);

extern void md_stop(mddev_t *mddev);

extern void md_stop_writes(mddev_t *mddev);

extern void md_rdev_init(mdk_rdev_t *rdev);

extern int md_rdev_init(mdk_rdev_t *rdev);



extern void mddev_suspend(mddev_t *mddev);

extern void mddev_resume(mddev_t *mddev);