linux/fs/ocfs2/blockcheck.c
Joel Becker 73be192b17 ocfs2: Add statistics for the checksum and ecc operations.
It would be nice to know how often we get checksum failures.  Even
better, how many of them we can fix with the single bit ecc.  So, we add
a statistics structure.  The structure can be installed into debugfs
wherever the user wants.

For ocfs2, we'll put it in the superblock-specific debugfs directory and
pass it down from our higher-level functions.  The stats are only
registered with debugfs when the filesystem supports metadata ecc.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
2009-06-03 19:15:36 -07:00

646 lines
16 KiB
C

/* -*- mode: c; c-basic-offset: 8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* blockcheck.c
*
* Checksum and ECC codes for the OCFS2 userspace library.
*
* Copyright (C) 2006, 2008 Oracle. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License, version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope that 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/kernel.h>
#include <linux/types.h>
#include <linux/crc32.h>
#include <linux/buffer_head.h>
#include <linux/bitops.h>
#include <linux/debugfs.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <asm/byteorder.h>
#include <cluster/masklog.h>
#include "ocfs2.h"
#include "blockcheck.h"
/*
* We use the following conventions:
*
* d = # data bits
* p = # parity bits
* c = # total code bits (d + p)
*/
/*
* Calculate the bit offset in the hamming code buffer based on the bit's
* offset in the data buffer. Since the hamming code reserves all
* power-of-two bits for parity, the data bit number and the code bit
* number are offest by all the parity bits beforehand.
*
* Recall that bit numbers in hamming code are 1-based. This function
* takes the 0-based data bit from the caller.
*
* An example. Take bit 1 of the data buffer. 1 is a power of two (2^0),
* so it's a parity bit. 2 is a power of two (2^1), so it's a parity bit.
* 3 is not a power of two. So bit 1 of the data buffer ends up as bit 3
* in the code buffer.
*
* The caller can pass in *p if it wants to keep track of the most recent
* number of parity bits added. This allows the function to start the
* calculation at the last place.
*/
static unsigned int calc_code_bit(unsigned int i, unsigned int *p_cache)
{
unsigned int b, p = 0;
/*
* Data bits are 0-based, but we're talking code bits, which
* are 1-based.
*/
b = i + 1;
/* Use the cache if it is there */
if (p_cache)
p = *p_cache;
b += p;
/*
* For every power of two below our bit number, bump our bit.
*
* We compare with (b + 1) because we have to compare with what b
* would be _if_ it were bumped up by the parity bit. Capice?
*
* p is set above.
*/
for (; (1 << p) < (b + 1); p++)
b++;
if (p_cache)
*p_cache = p;
return b;
}
/*
* This is the low level encoder function. It can be called across
* multiple hunks just like the crc32 code. 'd' is the number of bits
* _in_this_hunk_. nr is the bit offset of this hunk. So, if you had
* two 512B buffers, you would do it like so:
*
* parity = ocfs2_hamming_encode(0, buf1, 512 * 8, 0);
* parity = ocfs2_hamming_encode(parity, buf2, 512 * 8, 512 * 8);
*
* If you just have one buffer, use ocfs2_hamming_encode_block().
*/
u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr)
{
unsigned int i, b, p = 0;
BUG_ON(!d);
/*
* b is the hamming code bit number. Hamming code specifies a
* 1-based array, but C uses 0-based. So 'i' is for C, and 'b' is
* for the algorithm.
*
* The i++ in the for loop is so that the start offset passed
* to ocfs2_find_next_bit_set() is one greater than the previously
* found bit.
*/
for (i = 0; (i = ocfs2_find_next_bit(data, d, i)) < d; i++)
{
/*
* i is the offset in this hunk, nr + i is the total bit
* offset.
*/
b = calc_code_bit(nr + i, &p);
/*
* Data bits in the resultant code are checked by
* parity bits that are part of the bit number
* representation. Huh?
*
* <wikipedia href="http://en.wikipedia.org/wiki/Hamming_code">
* In other words, the parity bit at position 2^k
* checks bits in positions having bit k set in
* their binary representation. Conversely, for
* instance, bit 13, i.e. 1101(2), is checked by
* bits 1000(2) = 8, 0100(2)=4 and 0001(2) = 1.
* </wikipedia>
*
* Note that 'k' is the _code_ bit number. 'b' in
* our loop.
*/
parity ^= b;
}
/* While the data buffer was treated as little endian, the
* return value is in host endian. */
return parity;
}
u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize)
{
return ocfs2_hamming_encode(0, data, blocksize * 8, 0);
}
/*
* Like ocfs2_hamming_encode(), this can handle hunks. nr is the bit
* offset of the current hunk. If bit to be fixed is not part of the
* current hunk, this does nothing.
*
* If you only have one hunk, use ocfs2_hamming_fix_block().
*/
void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr,
unsigned int fix)
{
unsigned int i, b;
BUG_ON(!d);
/*
* If the bit to fix has an hweight of 1, it's a parity bit. One
* busted parity bit is its own error. Nothing to do here.
*/
if (hweight32(fix) == 1)
return;
/*
* nr + d is the bit right past the data hunk we're looking at.
* If fix after that, nothing to do
*/
if (fix >= calc_code_bit(nr + d, NULL))
return;
/*
* nr is the offset in the data hunk we're starting at. Let's
* start b at the offset in the code buffer. See hamming_encode()
* for a more detailed description of 'b'.
*/
b = calc_code_bit(nr, NULL);
/* If the fix is before this hunk, nothing to do */
if (fix < b)
return;
for (i = 0; i < d; i++, b++)
{
/* Skip past parity bits */
while (hweight32(b) == 1)
b++;
/*
* i is the offset in this data hunk.
* nr + i is the offset in the total data buffer.
* b is the offset in the total code buffer.
*
* Thus, when b == fix, bit i in the current hunk needs
* fixing.
*/
if (b == fix)
{
if (ocfs2_test_bit(i, data))
ocfs2_clear_bit(i, data);
else
ocfs2_set_bit(i, data);
break;
}
}
}
void ocfs2_hamming_fix_block(void *data, unsigned int blocksize,
unsigned int fix)
{
ocfs2_hamming_fix(data, blocksize * 8, 0, fix);
}
/*
* Debugfs handling.
*/
#ifdef CONFIG_DEBUG_FS
static int blockcheck_u64_get(void *data, u64 *val)
{
*val = *(u64 *)data;
return 0;
}
DEFINE_SIMPLE_ATTRIBUTE(blockcheck_fops, blockcheck_u64_get, NULL, "%llu\n");
static struct dentry *blockcheck_debugfs_create(const char *name,
struct dentry *parent,
u64 *value)
{
return debugfs_create_file(name, S_IFREG | S_IRUSR, parent, value,
&blockcheck_fops);
}
static void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
{
if (stats) {
debugfs_remove(stats->b_debug_check);
stats->b_debug_check = NULL;
debugfs_remove(stats->b_debug_failure);
stats->b_debug_failure = NULL;
debugfs_remove(stats->b_debug_recover);
stats->b_debug_recover = NULL;
debugfs_remove(stats->b_debug_dir);
stats->b_debug_dir = NULL;
}
}
static int ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
struct dentry *parent)
{
int rc = -EINVAL;
if (!stats)
goto out;
stats->b_debug_dir = debugfs_create_dir("blockcheck", parent);
if (!stats->b_debug_dir)
goto out;
stats->b_debug_check =
blockcheck_debugfs_create("blocks_checked",
stats->b_debug_dir,
&stats->b_check_count);
stats->b_debug_failure =
blockcheck_debugfs_create("checksums_failed",
stats->b_debug_dir,
&stats->b_failure_count);
stats->b_debug_recover =
blockcheck_debugfs_create("ecc_recoveries",
stats->b_debug_dir,
&stats->b_recover_count);
if (stats->b_debug_check && stats->b_debug_failure &&
stats->b_debug_recover)
rc = 0;
out:
if (rc)
ocfs2_blockcheck_debug_remove(stats);
return rc;
}
#else
static inline int ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
struct dentry *parent)
{
return 0;
}
static inline void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
{
}
#endif /* CONFIG_DEBUG_FS */
/* Always-called wrappers for starting and stopping the debugfs files */
int ocfs2_blockcheck_stats_debugfs_install(struct ocfs2_blockcheck_stats *stats,
struct dentry *parent)
{
return ocfs2_blockcheck_debug_install(stats, parent);
}
void ocfs2_blockcheck_stats_debugfs_remove(struct ocfs2_blockcheck_stats *stats)
{
ocfs2_blockcheck_debug_remove(stats);
}
static void ocfs2_blockcheck_inc_check(struct ocfs2_blockcheck_stats *stats)
{
u64 new_count;
if (!stats)
return;
spin_lock(&stats->b_lock);
stats->b_check_count++;
new_count = stats->b_check_count;
spin_unlock(&stats->b_lock);
if (!new_count)
mlog(ML_NOTICE, "Block check count has wrapped\n");
}
static void ocfs2_blockcheck_inc_failure(struct ocfs2_blockcheck_stats *stats)
{
u64 new_count;
if (!stats)
return;
spin_lock(&stats->b_lock);
stats->b_failure_count++;
new_count = stats->b_failure_count;
spin_unlock(&stats->b_lock);
if (!new_count)
mlog(ML_NOTICE, "Checksum failure count has wrapped\n");
}
static void ocfs2_blockcheck_inc_recover(struct ocfs2_blockcheck_stats *stats)
{
u64 new_count;
if (!stats)
return;
spin_lock(&stats->b_lock);
stats->b_recover_count++;
new_count = stats->b_recover_count;
spin_unlock(&stats->b_lock);
if (!new_count)
mlog(ML_NOTICE, "ECC recovery count has wrapped\n");
}
/*
* These are the low-level APIs for using the ocfs2_block_check structure.
*/
/*
* This function generates check information for a block.
* data is the block to be checked. bc is a pointer to the
* ocfs2_block_check structure describing the crc32 and the ecc.
*
* bc should be a pointer inside data, as the function will
* take care of zeroing it before calculating the check information. If
* bc does not point inside data, the caller must make sure any inline
* ocfs2_block_check structures are zeroed.
*
* The data buffer must be in on-disk endian (little endian for ocfs2).
* bc will be filled with little-endian values and will be ready to go to
* disk.
*/
void ocfs2_block_check_compute(void *data, size_t blocksize,
struct ocfs2_block_check *bc)
{
u32 crc;
u32 ecc;
memset(bc, 0, sizeof(struct ocfs2_block_check));
crc = crc32_le(~0, data, blocksize);
ecc = ocfs2_hamming_encode_block(data, blocksize);
/*
* No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
* larger than 16 bits.
*/
BUG_ON(ecc > USHORT_MAX);
bc->bc_crc32e = cpu_to_le32(crc);
bc->bc_ecc = cpu_to_le16((u16)ecc);
}
/*
* This function validates existing check information. Like _compute,
* the function will take care of zeroing bc before calculating check codes.
* If bc is not a pointer inside data, the caller must have zeroed any
* inline ocfs2_block_check structures.
*
* Again, the data passed in should be the on-disk endian.
*/
int ocfs2_block_check_validate(void *data, size_t blocksize,
struct ocfs2_block_check *bc,
struct ocfs2_blockcheck_stats *stats)
{
int rc = 0;
struct ocfs2_block_check check;
u32 crc, ecc;
ocfs2_blockcheck_inc_check(stats);
check.bc_crc32e = le32_to_cpu(bc->bc_crc32e);
check.bc_ecc = le16_to_cpu(bc->bc_ecc);
memset(bc, 0, sizeof(struct ocfs2_block_check));
/* Fast path - if the crc32 validates, we're good to go */
crc = crc32_le(~0, data, blocksize);
if (crc == check.bc_crc32e)
goto out;
ocfs2_blockcheck_inc_failure(stats);
mlog(ML_ERROR,
"CRC32 failed: stored: %u, computed %u. Applying ECC.\n",
(unsigned int)check.bc_crc32e, (unsigned int)crc);
/* Ok, try ECC fixups */
ecc = ocfs2_hamming_encode_block(data, blocksize);
ocfs2_hamming_fix_block(data, blocksize, ecc ^ check.bc_ecc);
/* And check the crc32 again */
crc = crc32_le(~0, data, blocksize);
if (crc == check.bc_crc32e) {
ocfs2_blockcheck_inc_recover(stats);
goto out;
}
mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
(unsigned int)check.bc_crc32e, (unsigned int)crc);
rc = -EIO;
out:
bc->bc_crc32e = cpu_to_le32(check.bc_crc32e);
bc->bc_ecc = cpu_to_le16(check.bc_ecc);
return rc;
}
/*
* This function generates check information for a list of buffer_heads.
* bhs is the blocks to be checked. bc is a pointer to the
* ocfs2_block_check structure describing the crc32 and the ecc.
*
* bc should be a pointer inside data, as the function will
* take care of zeroing it before calculating the check information. If
* bc does not point inside data, the caller must make sure any inline
* ocfs2_block_check structures are zeroed.
*
* The data buffer must be in on-disk endian (little endian for ocfs2).
* bc will be filled with little-endian values and will be ready to go to
* disk.
*/
void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr,
struct ocfs2_block_check *bc)
{
int i;
u32 crc, ecc;
BUG_ON(nr < 0);
if (!nr)
return;
memset(bc, 0, sizeof(struct ocfs2_block_check));
for (i = 0, crc = ~0, ecc = 0; i < nr; i++) {
crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
/*
* The number of bits in a buffer is obviously b_size*8.
* The offset of this buffer is b_size*i, so the bit offset
* of this buffer is b_size*8*i.
*/
ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
bhs[i]->b_size * 8,
bhs[i]->b_size * 8 * i);
}
/*
* No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
* larger than 16 bits.
*/
BUG_ON(ecc > USHORT_MAX);
bc->bc_crc32e = cpu_to_le32(crc);
bc->bc_ecc = cpu_to_le16((u16)ecc);
}
/*
* This function validates existing check information on a list of
* buffer_heads. Like _compute_bhs, the function will take care of
* zeroing bc before calculating check codes. If bc is not a pointer
* inside data, the caller must have zeroed any inline
* ocfs2_block_check structures.
*
* Again, the data passed in should be the on-disk endian.
*/
int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr,
struct ocfs2_block_check *bc,
struct ocfs2_blockcheck_stats *stats)
{
int i, rc = 0;
struct ocfs2_block_check check;
u32 crc, ecc, fix;
BUG_ON(nr < 0);
if (!nr)
return 0;
ocfs2_blockcheck_inc_check(stats);
check.bc_crc32e = le32_to_cpu(bc->bc_crc32e);
check.bc_ecc = le16_to_cpu(bc->bc_ecc);
memset(bc, 0, sizeof(struct ocfs2_block_check));
/* Fast path - if the crc32 validates, we're good to go */
for (i = 0, crc = ~0; i < nr; i++)
crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
if (crc == check.bc_crc32e)
goto out;
ocfs2_blockcheck_inc_failure(stats);
mlog(ML_ERROR,
"CRC32 failed: stored: %u, computed %u. Applying ECC.\n",
(unsigned int)check.bc_crc32e, (unsigned int)crc);
/* Ok, try ECC fixups */
for (i = 0, ecc = 0; i < nr; i++) {
/*
* The number of bits in a buffer is obviously b_size*8.
* The offset of this buffer is b_size*i, so the bit offset
* of this buffer is b_size*8*i.
*/
ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
bhs[i]->b_size * 8,
bhs[i]->b_size * 8 * i);
}
fix = ecc ^ check.bc_ecc;
for (i = 0; i < nr; i++) {
/*
* Try the fix against each buffer. It will only affect
* one of them.
*/
ocfs2_hamming_fix(bhs[i]->b_data, bhs[i]->b_size * 8,
bhs[i]->b_size * 8 * i, fix);
}
/* And check the crc32 again */
for (i = 0, crc = ~0; i < nr; i++)
crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
if (crc == check.bc_crc32e) {
ocfs2_blockcheck_inc_recover(stats);
goto out;
}
mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
(unsigned int)check.bc_crc32e, (unsigned int)crc);
rc = -EIO;
out:
bc->bc_crc32e = cpu_to_le32(check.bc_crc32e);
bc->bc_ecc = cpu_to_le16(check.bc_ecc);
return rc;
}
/*
* These are the main API. They check the superblock flag before
* calling the underlying operations.
*
* They expect the buffer(s) to be in disk format.
*/
void ocfs2_compute_meta_ecc(struct super_block *sb, void *data,
struct ocfs2_block_check *bc)
{
if (ocfs2_meta_ecc(OCFS2_SB(sb)))
ocfs2_block_check_compute(data, sb->s_blocksize, bc);
}
int ocfs2_validate_meta_ecc(struct super_block *sb, void *data,
struct ocfs2_block_check *bc)
{
int rc = 0;
struct ocfs2_super *osb = OCFS2_SB(sb);
if (ocfs2_meta_ecc(osb))
rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc,
&osb->osb_ecc_stats);
return rc;
}
void ocfs2_compute_meta_ecc_bhs(struct super_block *sb,
struct buffer_head **bhs, int nr,
struct ocfs2_block_check *bc)
{
if (ocfs2_meta_ecc(OCFS2_SB(sb)))
ocfs2_block_check_compute_bhs(bhs, nr, bc);
}
int ocfs2_validate_meta_ecc_bhs(struct super_block *sb,
struct buffer_head **bhs, int nr,
struct ocfs2_block_check *bc)
{
int rc = 0;
struct ocfs2_super *osb = OCFS2_SB(sb);
if (ocfs2_meta_ecc(osb))
rc = ocfs2_block_check_validate_bhs(bhs, nr, bc,
&osb->osb_ecc_stats);
return rc;
}