block/badblocks.c - linux/kernel/git/davem/net - Git at Google

 // 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>

 /**
  * 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;
 		sectors = target - s;
 	}
 	/* '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;
 		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) &&
 		    (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);
	// 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>

	/**
	* 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;
	sectors = target - s;
	}
	/* '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;
	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) &&
	(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);