Commit 9e0e252a authored by Vishal Verma's avatar Vishal Verma Committed by Dan Williams

badblocks: Add core badblock management code

Take the core badblocks implementation from md, and make it generally
available. This follows the same style as kernel implementations of
linked lists, rb-trees etc, where you can have a structure that can be
embedded anywhere, and accessor functions to manipulate the data.

The only changes in this copy of the code are ones to generalize
function/variable names from md-specific ones. Also add init and free
functions.
Signed-off-by: default avatarVishal Verma <vishal.l.verma@intel.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent ac34f15e
......@@ -8,7 +8,7 @@ obj-$(CONFIG_BLOCK) := bio.o elevator.o blk-core.o blk-tag.o blk-sysfs.o \
blk-iopoll.o blk-lib.o blk-mq.o blk-mq-tag.o \
blk-mq-sysfs.o blk-mq-cpu.o blk-mq-cpumap.o ioctl.o \
genhd.o scsi_ioctl.o partition-generic.o ioprio.o \
partitions/
badblocks.o partitions/
obj-$(CONFIG_BOUNCE) += bounce.o
obj-$(CONFIG_BLK_DEV_BSG) += bsg.o
......
/*
* Bad block management
*
* - Heavily based on MD badblocks code from Neil Brown
*
* Copyright (c) 2015, Intel Corporation.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*/
#include <linux/badblocks.h>
#include <linux/seqlock.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);
/**
* 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 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_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;
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) {
/* 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) {
/* 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;
}
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;
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);
/**
* 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)
{
bb->count = 0;
if (enable)
bb->shift = 0;
else
bb->shift = -1;
bb->page = kzalloc(PAGE_SIZE, GFP_KERNEL);
if (bb->page == (u64 *)0) {
bb->shift = -1;
return -ENOMEM;
}
seqlock_init(&bb->lock);
return 0;
}
EXPORT_SYMBOL_GPL(badblocks_init);
/**
* badblocks_free() - free the badblocks structure
* @bb: the badblocks structure that holds all badblock information
*/
void badblocks_free(struct badblocks *bb)
{
kfree(bb->page);
bb->page = NULL;
}
EXPORT_SYMBOL_GPL(badblocks_free);
#ifndef _LINUX_BADBLOCKS_H
#define _LINUX_BADBLOCKS_H
#include <linux/seqlock.h>
#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/types.h>
#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))
/* 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 MAX_BADBLOCKS (PAGE_SIZE/8)
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 */
};
int badblocks_check(struct badblocks *bb, sector_t s, int sectors,
sector_t *first_bad, int *bad_sectors);
int badblocks_set(struct badblocks *bb, sector_t s, int sectors,
int acknowledged);
int badblocks_clear(struct badblocks *bb, sector_t s, int sectors);
void ack_all_badblocks(struct badblocks *bb);
ssize_t badblocks_show(struct badblocks *bb, char *page, int unack);
ssize_t badblocks_store(struct badblocks *bb, const char *page, size_t len,
int unack);
int badblocks_init(struct badblocks *bb, int enable);
void badblocks_free(struct badblocks *bb);
#endif
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