badblocks: add helper routines for badblock ranges handling

[thirdparty/linux.git] / block / badblocks.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Bad block management
 *
 * - Heavily based on MD badblocks code from Neil Brown
 *
 * Copyright (c) 2015, Intel Corporation.
 */

#include <linux/badblocks.h>
#include <linux/seqlock.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/stddef.h>
#include <linux/types.h>
#include <linux/slab.h>

/*
 * Find the range starts at-or-before 's' from bad table. The search
 * starts from index 'hint' and stops at index 'hint_end' from the bad
 * table.
 */
static int prev_by_hint(struct badblocks *bb, sector_t s, int hint)
{
	int hint_end = hint + 2;
	u64 *p = bb->page;
	int ret = -1;

	while ((hint < hint_end) && ((hint + 1) <= bb->count) &&
	       (BB_OFFSET(p[hint]) <= s)) {
		if ((hint + 1) == bb->count || BB_OFFSET(p[hint + 1]) > s) {
			ret = hint;
			break;
		}
		hint++;
	}

	return ret;
}

/*
 * Find the range starts at-or-before bad->start. If 'hint' is provided
 * (hint >= 0) then search in the bad table from hint firstly. It is
 * very probably the wanted bad range can be found from the hint index,
 * then the unnecessary while-loop iteration can be avoided.
 */
static int prev_badblocks(struct badblocks *bb, struct badblocks_context *bad,
			  int hint)
{
	sector_t s = bad->start;
	int ret = -1;
	int lo, hi;
	u64 *p;

	if (!bb->count)
		goto out;

	if (hint >= 0) {
		ret = prev_by_hint(bb, s, hint);
		if (ret >= 0)
			goto out;
	}

	lo = 0;
	hi = bb->count;
	p = bb->page;

	/* The following bisect search might be unnecessary */
	if (BB_OFFSET(p[lo]) > s)
		return -1;
	if (BB_OFFSET(p[hi - 1]) <= s)
		return hi - 1;

	/* Do bisect search in bad table */
	while (hi - lo > 1) {
		int mid = (lo + hi)/2;
		sector_t a = BB_OFFSET(p[mid]);

		if (a == s) {
			ret = mid;
			goto out;
		}

		if (a < s)
			lo = mid;
		else
			hi = mid;
	}

	if (BB_OFFSET(p[lo]) <= s)
		ret = lo;
out:
	return ret;
}

/*
 * Return 'true' if the range indicated by 'bad' can be backward merged
 * with the bad range (from the bad table) index by 'behind'.
 */
static bool can_merge_behind(struct badblocks *bb,
			     struct badblocks_context *bad, int behind)
{
	sector_t sectors = bad->len;
	sector_t s = bad->start;
	u64 *p = bb->page;

	if ((s < BB_OFFSET(p[behind])) &&
	    ((s + sectors) >= BB_OFFSET(p[behind])) &&
	    ((BB_END(p[behind]) - s) <= BB_MAX_LEN) &&
	    BB_ACK(p[behind]) == bad->ack)
		return true;
	return false;
}

/*
 * Do backward merge for range indicated by 'bad' and the bad range
 * (from the bad table) indexed by 'behind'. The return value is merged
 * sectors from bad->len.
 */
static int behind_merge(struct badblocks *bb, struct badblocks_context *bad,
			int behind)
{
	sector_t sectors = bad->len;
	sector_t s = bad->start;
	u64 *p = bb->page;
	int merged = 0;

	WARN_ON(s >= BB_OFFSET(p[behind]));
	WARN_ON((s + sectors) < BB_OFFSET(p[behind]));

	if (s < BB_OFFSET(p[behind])) {
		merged = BB_OFFSET(p[behind]) - s;
		p[behind] =  BB_MAKE(s, BB_LEN(p[behind]) + merged, bad->ack);

		WARN_ON((BB_LEN(p[behind]) + merged) >= BB_MAX_LEN);
	}

	return merged;
}

/*
 * Return 'true' if the range indicated by 'bad' can be forward
 * merged with the bad range (from the bad table) indexed by 'prev'.
 */
static bool can_merge_front(struct badblocks *bb, int prev,
			    struct badblocks_context *bad)
{
	sector_t s = bad->start;
	u64 *p = bb->page;

	if (BB_ACK(p[prev]) == bad->ack &&
	    (s < BB_END(p[prev]) ||
	     (s == BB_END(p[prev]) && (BB_LEN(p[prev]) < BB_MAX_LEN))))
		return true;
	return false;
}

/*
 * Do forward merge for range indicated by 'bad' and the bad range
 * (from bad table) indexed by 'prev'. The return value is sectors
 * merged from bad->len.
 */
static int front_merge(struct badblocks *bb, int prev, struct badblocks_context *bad)
{
	sector_t sectors = bad->len;
	sector_t s = bad->start;
	u64 *p = bb->page;
	int merged = 0;

	WARN_ON(s > BB_END(p[prev]));

	if (s < BB_END(p[prev])) {
		merged = min_t(sector_t, sectors, BB_END(p[prev]) - s);
	} else {
		merged = min_t(sector_t, sectors, BB_MAX_LEN - BB_LEN(p[prev]));
		if ((prev + 1) < bb->count &&
		    merged > (BB_OFFSET(p[prev + 1]) - BB_END(p[prev]))) {
			merged = BB_OFFSET(p[prev + 1]) - BB_END(p[prev]);
		}

		p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
				  BB_LEN(p[prev]) + merged, bad->ack);
	}

	return merged;
}

/*
 * 'Combine' is a special case which can_merge_front() is not able to
 * handle: If a bad range (indexed by 'prev' from bad table) exactly
 * starts as bad->start, and the bad range ahead of 'prev' (indexed by
 * 'prev - 1' from bad table) exactly ends at where 'prev' starts, and
 * the sum of their lengths does not exceed BB_MAX_LEN limitation, then
 * these two bad range (from bad table) can be combined.
 *
 * Return 'true' if bad ranges indexed by 'prev' and 'prev - 1' from bad
 * table can be combined.
 */
static bool can_combine_front(struct badblocks *bb, int prev,
			      struct badblocks_context *bad)
{
	u64 *p = bb->page;

	if ((prev > 0) &&
	    (BB_OFFSET(p[prev]) == bad->start) &&
	    (BB_END(p[prev - 1]) == BB_OFFSET(p[prev])) &&
	    (BB_LEN(p[prev - 1]) + BB_LEN(p[prev]) <= BB_MAX_LEN) &&
	    (BB_ACK(p[prev - 1]) == BB_ACK(p[prev])))
		return true;
	return false;
}

/*
 * Combine the bad ranges indexed by 'prev' and 'prev - 1' (from bad
 * table) into one larger bad range, and the new range is indexed by
 * 'prev - 1'.
 * The caller of front_combine() will decrease bb->count, therefore
 * it is unnecessary to clear p[perv] after front merge.
 */
static void front_combine(struct badblocks *bb, int prev)
{
	u64 *p = bb->page;

	p[prev - 1] = BB_MAKE(BB_OFFSET(p[prev - 1]),
			      BB_LEN(p[prev - 1]) + BB_LEN(p[prev]),
			      BB_ACK(p[prev]));
	if ((prev + 1) < bb->count)
		memmove(p + prev, p + prev + 1, (bb->count - prev - 1) * 8);
}

/*
 * Return 'true' if the range indicated by 'bad' is exactly forward
 * overlapped with the bad range (from bad table) indexed by 'front'.
 * Exactly forward overlap means the bad range (from bad table) indexed
 * by 'prev' does not cover the whole range indicated by 'bad'.
 */
static bool overlap_front(struct badblocks *bb, int front,
			  struct badblocks_context *bad)
{
	u64 *p = bb->page;

	if (bad->start >= BB_OFFSET(p[front]) &&
	    bad->start < BB_END(p[front]))
		return true;
	return false;
}

/*
 * Return 'true' if the range indicated by 'bad' is exactly backward
 * overlapped with the bad range (from bad table) indexed by 'behind'.
 */
static bool overlap_behind(struct badblocks *bb, struct badblocks_context *bad,
			   int behind)
{
	u64 *p = bb->page;

	if (bad->start < BB_OFFSET(p[behind]) &&
	    (bad->start + bad->len) > BB_OFFSET(p[behind]))
		return true;
	return false;
}

/*
 * Return 'true' if the range indicated by 'bad' can overwrite the bad
 * range (from bad table) indexed by 'prev'.
 *
 * The range indicated by 'bad' can overwrite the bad range indexed by
 * 'prev' when,
 * 1) The whole range indicated by 'bad' can cover partial or whole bad
 *    range (from bad table) indexed by 'prev'.
 * 2) The ack value of 'bad' is larger or equal to the ack value of bad
 *    range 'prev'.
 *
 * If the overwriting doesn't cover the whole bad range (from bad table)
 * indexed by 'prev', new range might be split from existing bad range,
 * 1) The overwrite covers head or tail part of existing bad range, 1
 *    extra bad range will be split and added into the bad table.
 * 2) The overwrite covers middle of existing bad range, 2 extra bad
 *    ranges will be split (ahead and after the overwritten range) and
 *    added into the bad table.
 * The number of extra split ranges of the overwriting is stored in
 * 'extra' and returned for the caller.
 */
static bool can_front_overwrite(struct badblocks *bb, int prev,
				struct badblocks_context *bad, int *extra)
{
	u64 *p = bb->page;
	int len;

	WARN_ON(!overlap_front(bb, prev, bad));

	if (BB_ACK(p[prev]) >= bad->ack)
		return false;

	if (BB_END(p[prev]) <= (bad->start + bad->len)) {
		len = BB_END(p[prev]) - bad->start;
		if (BB_OFFSET(p[prev]) == bad->start)
			*extra = 0;
		else
			*extra = 1;

		bad->len = len;
	} else {
		if (BB_OFFSET(p[prev]) == bad->start)
			*extra = 1;
		else
		/*
		 * prev range will be split into two, beside the overwritten
		 * one, an extra slot needed from bad table.
		 */
			*extra = 2;
	}

	if ((bb->count + (*extra)) >= MAX_BADBLOCKS)
		return false;

	return true;
}

/*
 * Do the overwrite from the range indicated by 'bad' to the bad range
 * (from bad table) indexed by 'prev'.
 * The previously called can_front_overwrite() will provide how many
 * extra bad range(s) might be split and added into the bad table. All
 * the splitting cases in the bad table will be handled here.
 */
static int front_overwrite(struct badblocks *bb, int prev,
			   struct badblocks_context *bad, int extra)
{
	u64 *p = bb->page;
	sector_t orig_end = BB_END(p[prev]);
	int orig_ack = BB_ACK(p[prev]);

	switch (extra) {
	case 0:
		p[prev] = BB_MAKE(BB_OFFSET(p[prev]), BB_LEN(p[prev]),
				  bad->ack);
		break;
	case 1:
		if (BB_OFFSET(p[prev]) == bad->start) {
			p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
					  bad->len, bad->ack);
			memmove(p + prev + 2, p + prev + 1,
				(bb->count - prev - 1) * 8);
			p[prev + 1] = BB_MAKE(bad->start + bad->len,
					      orig_end - BB_END(p[prev]),
					      orig_ack);
		} else {
			p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
					  bad->start - BB_OFFSET(p[prev]),
					  orig_ack);
			/*
			 * prev +2 -> prev + 1 + 1, which is for,
			 * 1) prev + 1: the slot index of the previous one
			 * 2) + 1: one more slot for extra being 1.
			 */
			memmove(p + prev + 2, p + prev + 1,
				(bb->count - prev - 1) * 8);
			p[prev + 1] = BB_MAKE(bad->start, bad->len, bad->ack);
		}
		break;
	case 2:
		p[prev] = BB_MAKE(BB_OFFSET(p[prev]),
				  bad->start - BB_OFFSET(p[prev]),
				  orig_ack);
		/*
		 * prev + 3 -> prev + 1 + 2, which is for,
		 * 1) prev + 1: the slot index of the previous one
		 * 2) + 2: two more slots for extra being 2.
		 */
		memmove(p + prev + 3, p + prev + 1,
			(bb->count - prev - 1) * 8);
		p[prev + 1] = BB_MAKE(bad->start, bad->len, bad->ack);
		p[prev + 2] = BB_MAKE(BB_END(p[prev + 1]),
				      orig_end - BB_END(p[prev + 1]),
				      orig_ack);
		break;
	default:
		break;
	}

	return bad->len;
}

/*
 * Explicitly insert a range indicated by 'bad' to the bad table, where
 * the location is indexed by 'at'.
 */
static int insert_at(struct badblocks *bb, int at, struct badblocks_context *bad)
{
	u64 *p = bb->page;
	int len;

	WARN_ON(badblocks_full(bb));

	len = min_t(sector_t, bad->len, BB_MAX_LEN);
	if (at < bb->count)
		memmove(p + at + 1, p + at, (bb->count - at) * 8);
	p[at] = BB_MAKE(bad->start, len, bad->ack);

	return len;
}

/**
 * badblocks_check() - check a given range for bad sectors
 * @bb:		the badblocks structure that holds all badblock information
 * @s:		sector (start) at which to check for badblocks
 * @sectors:	number of sectors to check for badblocks
 * @first_bad:	pointer to store location of the first badblock
 * @bad_sectors: pointer to store number of badblocks after @first_bad
 *
 * 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 badblocks_check
 * 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.
 *
 * Return:
 *  0: there are no known bad blocks in the range
 *  1: there are known bad block which are all acknowledged
 * -1: there are bad blocks which have not yet been acknowledged in metadata.
 * plus the start/length of the first bad section we overlap.
 */
int badblocks_check(struct badblocks *bb, sector_t s, int sectors,
			sector_t *first_bad, int *bad_sectors)
{
	int hi;
	int lo;
	u64 *p = bb->page;
	int rv;
	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;
	}
	/* 'target' is now the first block after the bad range */

retry:
	seq = read_seqbegin(&bb->lock);
	lo = 0;
	rv = 0;
	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(badblocks_check);

static void badblocks_update_acked(struct badblocks *bb)
{
	u64 *p = bb->page;
	int i;
	bool unacked = false;

	if (!bb->unacked_exist)
		return;

	for (i = 0; i < bb->count ; i++) {
		if (!BB_ACK(p[i])) {
			unacked = true;
			break;
		}
	}

	if (!unacked)
		bb->unacked_exist = 0;
}

/**
 * badblocks_set() - Add a range of bad blocks to the table.
 * @bb:		the badblocks structure that holds all badblock information
 * @s:		first sector to mark as bad
 * @sectors:	number of sectors to mark as bad
 * @acknowledged: weather to mark the bad sectors as acknowledged
 *
 * 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.
 *
 * Return:
 *  0: success
 *  1: failed to set badblocks (out of space)
 */
int badblocks_set(struct badblocks *bb, sector_t s, int sectors,
			int acknowledged)
{
	u64 *p;
	int lo, hi;
	int rv = 0;
	unsigned long flags;

	if (bb->shift < 0)
		/* badblocks are disabled */
		return 1;

	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_irqsave(&bb->lock, flags);

	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 >= MAX_BADBLOCKS) {
			/* No room for more */
			rv = 1;
			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;
	if (!acknowledged)
		bb->unacked_exist = 1;
	else
		badblocks_update_acked(bb);
	write_sequnlock_irqrestore(&bb->lock, flags);

	return rv;
}
EXPORT_SYMBOL_GPL(badblocks_set);

/**
 * badblocks_clear() - Remove a range of bad blocks to the table.
 * @bb:		the badblocks structure that holds all badblock information
 * @s:		first sector to mark as bad
 * @sectors:	number of sectors to mark as bad
 *
 * 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.
 *
 * Return:
 *  0: success
 *  1: failed to clear badblocks
 */
int badblocks_clear(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;
	}

	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) &&
		    (BB_OFFSET(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 >= MAX_BADBLOCKS) {
					rv = -ENOSPC;
					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) &&
		       (BB_OFFSET(p[lo]) < target)) {
			/* 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);
		}
	}

	badblocks_update_acked(bb);
	bb->changed = 1;
out:
	write_sequnlock_irq(&bb->lock);
	return rv;
}
EXPORT_SYMBOL_GPL(badblocks_clear);

/**
 * ack_all_badblocks() - Acknowledge all bad blocks in a list.
 * @bb:		the badblocks structure that holds all badblock information
 *
 * This only succeeds if ->changed is clear.  It is used by
 * in-kernel metadata updates
 */
void 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 && bb->unacked_exist) {
		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);
			}
		}
		bb->unacked_exist = 0;
	}
	write_sequnlock_irq(&bb->lock);
}
EXPORT_SYMBOL_GPL(ack_all_badblocks);

/**
 * badblocks_show() - sysfs access to bad-blocks list
 * @bb:		the badblocks structure that holds all badblock information
 * @page:	buffer received from sysfs
 * @unack:	weather to show unacknowledged badblocks
 *
 * Return:
 *  Length of returned data
 */
ssize_t badblocks_show(struct badblocks *bb, char *page, int unack)
{
	size_t len;
	int i;
	u64 *p = bb->page;
	unsigned seq;

	if (bb->shift < 0)
		return 0;

retry:
	seq = read_seqbegin(&bb->lock);

	len = 0;
	i = 0;

	while (len < PAGE_SIZE && i < bb->count) {
		sector_t s = BB_OFFSET(p[i]);
		unsigned int length = BB_LEN(p[i]);
		int ack = BB_ACK(p[i]);

		i++;

		if (unack && ack)
			continue;

		len += snprintf(page+len, PAGE_SIZE-len, "%llu %u\n",
				(unsigned long long)s << bb->shift,
				length << bb->shift);
	}
	if (unack && len == 0)
		bb->unacked_exist = 0;

	if (read_seqretry(&bb->lock, seq))
		goto retry;

	return len;
}
EXPORT_SYMBOL_GPL(badblocks_show);

/**
 * badblocks_store() - sysfs access to bad-blocks list
 * @bb:		the badblocks structure that holds all badblock information
 * @page:	buffer received from sysfs
 * @len:	length of data received from sysfs
 * @unack:	weather to show unacknowledged badblocks
 *
 * Return:
 *  Length of the buffer processed or -ve error.
 */
ssize_t badblocks_store(struct badblocks *bb, const char *page, size_t len,
			int unack)
{
	unsigned long long sector;
	int length;
	char newline;

	switch (sscanf(page, "%llu %d%c", &sector, &length, &newline)) {
	case 3:
		if (newline != '\n')
			return -EINVAL;
		fallthrough;
	case 2:
		if (length <= 0)
			return -EINVAL;
		break;
	default:
		return -EINVAL;
	}

	if (badblocks_set(bb, sector, length, !unack))
		return -ENOSPC;
	else
		return len;
}
EXPORT_SYMBOL_GPL(badblocks_store);

static int __badblocks_init(struct device *dev, struct badblocks *bb,
		int enable)
{
	bb->dev = dev;
	bb->count = 0;
	if (enable)
		bb->shift = 0;
	else
		bb->shift = -1;
	if (dev)
		bb->page = devm_kzalloc(dev, PAGE_SIZE, GFP_KERNEL);
	else
		bb->page = kzalloc(PAGE_SIZE, GFP_KERNEL);
	if (!bb->page) {
		bb->shift = -1;
		return -ENOMEM;
	}
	seqlock_init(&bb->lock);

	return 0;
}

/**
 * badblocks_init() - initialize the badblocks structure
 * @bb:		the badblocks structure that holds all badblock information
 * @enable:	weather to enable badblocks accounting
 *
 * Return:
 *  0: success
 *  -ve errno: on error
 */
int badblocks_init(struct badblocks *bb, int enable)
{
	return __badblocks_init(NULL, bb, enable);
}
EXPORT_SYMBOL_GPL(badblocks_init);

int devm_init_badblocks(struct device *dev, struct badblocks *bb)
{
	if (!bb)
		return -EINVAL;
	return __badblocks_init(dev, bb, 1);
}
EXPORT_SYMBOL_GPL(devm_init_badblocks);

/**
 * badblocks_exit() - free the badblocks structure
 * @bb:		the badblocks structure that holds all badblock information
 */
void badblocks_exit(struct badblocks *bb)
{
	if (!bb)
		return;
	if (bb->dev)
		devm_kfree(bb->dev, bb->page);
	else
		kfree(bb->page);
	bb->page = NULL;
}
EXPORT_SYMBOL_GPL(badblocks_exit);