diff options
| -rw-r--r-- | fs/ocfs2/Makefile | 1 | ||||
| -rw-r--r-- | fs/ocfs2/blockcheck.c | 480 | ||||
| -rw-r--r-- | fs/ocfs2/blockcheck.h | 82 | ||||
| -rw-r--r-- | fs/ocfs2/ocfs2.h | 8 |
4 files changed, 571 insertions, 0 deletions
diff --git a/fs/ocfs2/Makefile b/fs/ocfs2/Makefile index 7e4b361b755c..01596079dd63 100644 --- a/fs/ocfs2/Makefile +++ b/fs/ocfs2/Makefile @@ -12,6 +12,7 @@ obj-$(CONFIG_OCFS2_FS_USERSPACE_CLUSTER) += ocfs2_stack_user.o ocfs2-objs := \ alloc.o \ aops.o \ + blockcheck.o \ buffer_head_io.o \ dcache.o \ dir.o \ diff --git a/fs/ocfs2/blockcheck.c b/fs/ocfs2/blockcheck.c new file mode 100644 index 000000000000..2bf3d7f61aec --- /dev/null +++ b/fs/ocfs2/blockcheck.c @@ -0,0 +1,480 @@ +/* -*- 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 <asm/byteorder.h> + +#include "ocfs2.h" + +#include "blockcheck.h" + + + +/* + * We use the following conventions: + * + * d = # data bits + * p = # parity bits + * c = # total code bits (d + p) + */ +static int calc_parity_bits(unsigned int d) +{ + unsigned int p; + + /* + * Bits required for Single Error Correction is as follows: + * + * d + p + 1 <= 2^p + * + * We're restricting ourselves to 31 bits of parity, that should be + * sufficient. + */ + for (p = 1; p < 32; p++) + { + if ((d + p + 1) <= (1 << p)) + return p; + } + + return 0; +} + +/* + * 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. + */ +static unsigned int calc_code_bit(unsigned int i) +{ + unsigned int b, p; + + /* + * Data bits are 0-based, but we're talking code bits, which + * are 1-based. + */ + b = i + 1; + + /* + * For every power of two below our bit number, bump our bit. + * + * We compare with (b + 1) becuase we have to compare with what b + * would be _if_ it were bumped up by the parity bit. Capice? + */ + for (p = 0; (1 << p) < (b + 1); p++) + b++; + + 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 p = calc_parity_bits(nr + d); + unsigned int i, j, b; + + BUG_ON(!p); + + /* + * 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); + + for (j = 0; j < p; j++) + { + /* + * 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. + */ + if (b & (1 << j)) + parity ^= (1 << j); + } + } + + /* 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 p = calc_parity_bits(nr + d); + unsigned int i, b; + + BUG_ON(!p); + + /* + * 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)) + 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); + /* 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); +} + +/* + * 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) +{ + int rc = 0; + struct ocfs2_block_check check; + u32 crc, ecc; + + 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; + + /* 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) + goto out; + + 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) +{ + int i, rc = 0; + struct ocfs2_block_check check; + u32 crc, ecc, fix; + + BUG_ON(nr < 0); + + if (!nr) + return 0; + + 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; + + 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) + 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; + + if (ocfs2_meta_ecc(OCFS2_SB(sb))) + rc = ocfs2_block_check_validate(data, sb->s_blocksize, bc); + + 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; + + if (ocfs2_meta_ecc(OCFS2_SB(sb))) + rc = ocfs2_block_check_validate_bhs(bhs, nr, bc); + + return rc; +} + diff --git a/fs/ocfs2/blockcheck.h b/fs/ocfs2/blockcheck.h new file mode 100644 index 000000000000..70ec3feda32f --- /dev/null +++ b/fs/ocfs2/blockcheck.h @@ -0,0 +1,82 @@ +/* -*- mode: c; c-basic-offset: 8; -*- + * vim: noexpandtab sw=8 ts=8 sts=0: + * + * blockcheck.h + * + * Checksum and ECC codes for the OCFS2 userspace library. + * + * Copyright (C) 2004, 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. + */ + +#ifndef OCFS2_BLOCKCHECK_H +#define OCFS2_BLOCKCHECK_H + + +/* High level block API */ +void ocfs2_compute_meta_ecc(struct super_block *sb, void *data, + struct ocfs2_block_check *bc); +int ocfs2_validate_meta_ecc(struct super_block *sb, void *data, + struct ocfs2_block_check *bc); +void ocfs2_compute_meta_ecc_bhs(struct super_block *sb, + struct buffer_head **bhs, int nr, + struct ocfs2_block_check *bc); +int ocfs2_validate_meta_ecc_bhs(struct super_block *sb, + struct buffer_head **bhs, int nr, + struct ocfs2_block_check *bc); + +/* Lower level API */ +void ocfs2_block_check_compute(void *data, size_t blocksize, + struct ocfs2_block_check *bc); +int ocfs2_block_check_validate(void *data, size_t blocksize, + struct ocfs2_block_check *bc); +void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr, + struct ocfs2_block_check *bc); +int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr, + struct ocfs2_block_check *bc); + +/* + * Hamming code functions + */ + +/* + * Encoding hamming code parity bits for a buffer. + * + * 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); +/* + * Fix a buffer with a bit error. The 'fix' is the original parity + * xor'd with the parity calculated now. + * + * 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 buffer, use ocfs2_hamming_fix_block(). + */ +void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr, + unsigned int fix); + +/* Convenience wrappers for a single buffer of data */ +extern u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize); +extern void ocfs2_hamming_fix_block(void *data, unsigned int blocksize, + unsigned int fix); +#endif diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h index 5c777988042f..2bb389fe7397 100644 --- a/fs/ocfs2/ocfs2.h +++ b/fs/ocfs2/ocfs2.h @@ -382,6 +382,13 @@ static inline int ocfs2_supports_xattr(struct ocfs2_super *osb) return 0; } +static inline int ocfs2_meta_ecc(struct ocfs2_super *osb) +{ + if (osb->s_feature_incompat & OCFS2_FEATURE_INCOMPAT_META_ECC) + return 1; + return 0; +} + /* set / clear functions because cluster events can make these happen * in parallel so we want the transitions to be atomic. this also * means that any future flags osb_flags must be protected by spinlock @@ -615,5 +622,6 @@ static inline s16 ocfs2_get_inode_steal_slot(struct ocfs2_super *osb) #define ocfs2_clear_bit ext2_clear_bit #define ocfs2_test_bit ext2_test_bit #define ocfs2_find_next_zero_bit ext2_find_next_zero_bit +#define ocfs2_find_next_bit ext2_find_next_bit #endif /* OCFS2_H */ |