606 lines
15 KiB
C
606 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* blockcheck.c
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*
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* Checksum and ECC codes for the OCFS2 userspace library.
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*
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* Copyright (C) 2006, 2008 Oracle. All rights reserved.
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*/
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include <linux/crc32.h>
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#include <linux/buffer_head.h>
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#include <linux/bitops.h>
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#include <linux/debugfs.h>
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <asm/byteorder.h>
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#include <cluster/masklog.h>
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#include "ocfs2.h"
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#include "blockcheck.h"
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/*
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* We use the following conventions:
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*
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* d = # data bits
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* p = # parity bits
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* c = # total code bits (d + p)
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*/
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/*
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* Calculate the bit offset in the hamming code buffer based on the bit's
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* offset in the data buffer. Since the hamming code reserves all
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* power-of-two bits for parity, the data bit number and the code bit
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* number are offset by all the parity bits beforehand.
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*
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* Recall that bit numbers in hamming code are 1-based. This function
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* takes the 0-based data bit from the caller.
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*
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* An example. Take bit 1 of the data buffer. 1 is a power of two (2^0),
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* so it's a parity bit. 2 is a power of two (2^1), so it's a parity bit.
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* 3 is not a power of two. So bit 1 of the data buffer ends up as bit 3
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* in the code buffer.
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*
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* The caller can pass in *p if it wants to keep track of the most recent
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* number of parity bits added. This allows the function to start the
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* calculation at the last place.
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*/
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static unsigned int calc_code_bit(unsigned int i, unsigned int *p_cache)
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{
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unsigned int b, p = 0;
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/*
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* Data bits are 0-based, but we're talking code bits, which
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* are 1-based.
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*/
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b = i + 1;
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/* Use the cache if it is there */
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if (p_cache)
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p = *p_cache;
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b += p;
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/*
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* For every power of two below our bit number, bump our bit.
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*
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* We compare with (b + 1) because we have to compare with what b
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* would be _if_ it were bumped up by the parity bit. Capice?
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*
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* p is set above.
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*/
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for (; (1 << p) < (b + 1); p++)
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b++;
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if (p_cache)
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*p_cache = p;
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return b;
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}
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/*
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* This is the low level encoder function. It can be called across
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* multiple hunks just like the crc32 code. 'd' is the number of bits
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* _in_this_hunk_. nr is the bit offset of this hunk. So, if you had
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* two 512B buffers, you would do it like so:
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*
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* parity = ocfs2_hamming_encode(0, buf1, 512 * 8, 0);
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* parity = ocfs2_hamming_encode(parity, buf2, 512 * 8, 512 * 8);
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*
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* If you just have one buffer, use ocfs2_hamming_encode_block().
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*/
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u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr)
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{
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unsigned int i, b, p = 0;
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BUG_ON(!d);
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/*
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* b is the hamming code bit number. Hamming code specifies a
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* 1-based array, but C uses 0-based. So 'i' is for C, and 'b' is
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* for the algorithm.
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*
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* The i++ in the for loop is so that the start offset passed
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* to ocfs2_find_next_bit_set() is one greater than the previously
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* found bit.
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*/
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for (i = 0; (i = ocfs2_find_next_bit(data, d, i)) < d; i++)
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{
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/*
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* i is the offset in this hunk, nr + i is the total bit
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* offset.
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*/
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b = calc_code_bit(nr + i, &p);
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/*
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* Data bits in the resultant code are checked by
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* parity bits that are part of the bit number
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* representation. Huh?
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*
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* <wikipedia href="https://en.wikipedia.org/wiki/Hamming_code">
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* In other words, the parity bit at position 2^k
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* checks bits in positions having bit k set in
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* their binary representation. Conversely, for
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* instance, bit 13, i.e. 1101(2), is checked by
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* bits 1000(2) = 8, 0100(2)=4 and 0001(2) = 1.
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* </wikipedia>
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*
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* Note that 'k' is the _code_ bit number. 'b' in
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* our loop.
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*/
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parity ^= b;
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}
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/* While the data buffer was treated as little endian, the
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* return value is in host endian. */
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return parity;
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}
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u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize)
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{
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return ocfs2_hamming_encode(0, data, blocksize * 8, 0);
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}
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/*
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* Like ocfs2_hamming_encode(), this can handle hunks. nr is the bit
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* offset of the current hunk. If bit to be fixed is not part of the
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* current hunk, this does nothing.
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*
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* If you only have one hunk, use ocfs2_hamming_fix_block().
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*/
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void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr,
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unsigned int fix)
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{
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unsigned int i, b;
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BUG_ON(!d);
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/*
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* If the bit to fix has an hweight of 1, it's a parity bit. One
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* busted parity bit is its own error. Nothing to do here.
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*/
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if (hweight32(fix) == 1)
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return;
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/*
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* nr + d is the bit right past the data hunk we're looking at.
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* If fix after that, nothing to do
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*/
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if (fix >= calc_code_bit(nr + d, NULL))
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return;
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/*
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* nr is the offset in the data hunk we're starting at. Let's
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* start b at the offset in the code buffer. See hamming_encode()
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* for a more detailed description of 'b'.
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*/
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b = calc_code_bit(nr, NULL);
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/* If the fix is before this hunk, nothing to do */
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if (fix < b)
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return;
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for (i = 0; i < d; i++, b++)
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{
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/* Skip past parity bits */
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while (hweight32(b) == 1)
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b++;
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/*
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* i is the offset in this data hunk.
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* nr + i is the offset in the total data buffer.
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* b is the offset in the total code buffer.
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*
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* Thus, when b == fix, bit i in the current hunk needs
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* fixing.
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*/
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if (b == fix)
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{
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if (ocfs2_test_bit(i, data))
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ocfs2_clear_bit(i, data);
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else
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ocfs2_set_bit(i, data);
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break;
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}
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}
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}
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void ocfs2_hamming_fix_block(void *data, unsigned int blocksize,
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unsigned int fix)
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{
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ocfs2_hamming_fix(data, blocksize * 8, 0, fix);
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}
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/*
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* Debugfs handling.
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*/
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#ifdef CONFIG_DEBUG_FS
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static int blockcheck_u64_get(void *data, u64 *val)
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{
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*val = *(u64 *)data;
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return 0;
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}
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DEFINE_DEBUGFS_ATTRIBUTE(blockcheck_fops, blockcheck_u64_get, NULL, "%llu\n");
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static void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
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{
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if (stats) {
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debugfs_remove_recursive(stats->b_debug_dir);
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stats->b_debug_dir = NULL;
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}
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}
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static void ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
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struct dentry *parent)
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{
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struct dentry *dir;
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dir = debugfs_create_dir("blockcheck", parent);
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stats->b_debug_dir = dir;
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debugfs_create_file("blocks_checked", S_IFREG | S_IRUSR, dir,
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&stats->b_check_count, &blockcheck_fops);
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debugfs_create_file("checksums_failed", S_IFREG | S_IRUSR, dir,
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&stats->b_failure_count, &blockcheck_fops);
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debugfs_create_file("ecc_recoveries", S_IFREG | S_IRUSR, dir,
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&stats->b_recover_count, &blockcheck_fops);
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}
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#else
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static inline void ocfs2_blockcheck_debug_install(struct ocfs2_blockcheck_stats *stats,
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struct dentry *parent)
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{
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}
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static inline void ocfs2_blockcheck_debug_remove(struct ocfs2_blockcheck_stats *stats)
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{
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}
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#endif /* CONFIG_DEBUG_FS */
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/* Always-called wrappers for starting and stopping the debugfs files */
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void ocfs2_blockcheck_stats_debugfs_install(struct ocfs2_blockcheck_stats *stats,
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struct dentry *parent)
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{
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ocfs2_blockcheck_debug_install(stats, parent);
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}
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void ocfs2_blockcheck_stats_debugfs_remove(struct ocfs2_blockcheck_stats *stats)
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{
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ocfs2_blockcheck_debug_remove(stats);
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}
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static void ocfs2_blockcheck_inc_check(struct ocfs2_blockcheck_stats *stats)
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{
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u64 new_count;
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if (!stats)
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return;
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spin_lock(&stats->b_lock);
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stats->b_check_count++;
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new_count = stats->b_check_count;
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spin_unlock(&stats->b_lock);
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if (!new_count)
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mlog(ML_NOTICE, "Block check count has wrapped\n");
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}
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static void ocfs2_blockcheck_inc_failure(struct ocfs2_blockcheck_stats *stats)
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{
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u64 new_count;
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if (!stats)
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return;
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spin_lock(&stats->b_lock);
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stats->b_failure_count++;
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new_count = stats->b_failure_count;
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spin_unlock(&stats->b_lock);
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if (!new_count)
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mlog(ML_NOTICE, "Checksum failure count has wrapped\n");
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}
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static void ocfs2_blockcheck_inc_recover(struct ocfs2_blockcheck_stats *stats)
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{
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u64 new_count;
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if (!stats)
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return;
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spin_lock(&stats->b_lock);
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stats->b_recover_count++;
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new_count = stats->b_recover_count;
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spin_unlock(&stats->b_lock);
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if (!new_count)
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mlog(ML_NOTICE, "ECC recovery count has wrapped\n");
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}
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/*
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* These are the low-level APIs for using the ocfs2_block_check structure.
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*/
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/*
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* This function generates check information for a block.
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* data is the block to be checked. bc is a pointer to the
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* ocfs2_block_check structure describing the crc32 and the ecc.
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*
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* bc should be a pointer inside data, as the function will
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* take care of zeroing it before calculating the check information. If
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* bc does not point inside data, the caller must make sure any inline
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* ocfs2_block_check structures are zeroed.
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*
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* The data buffer must be in on-disk endian (little endian for ocfs2).
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* bc will be filled with little-endian values and will be ready to go to
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* disk.
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*/
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void ocfs2_block_check_compute(void *data, size_t blocksize,
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struct ocfs2_block_check *bc)
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{
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u32 crc;
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u32 ecc;
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memset(bc, 0, sizeof(struct ocfs2_block_check));
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crc = crc32_le(~0, data, blocksize);
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ecc = ocfs2_hamming_encode_block(data, blocksize);
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/*
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* No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
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* larger than 16 bits.
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*/
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BUG_ON(ecc > USHRT_MAX);
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bc->bc_crc32e = cpu_to_le32(crc);
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bc->bc_ecc = cpu_to_le16((u16)ecc);
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}
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/*
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* This function validates existing check information. Like _compute,
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* the function will take care of zeroing bc before calculating check codes.
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* If bc is not a pointer inside data, the caller must have zeroed any
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* inline ocfs2_block_check structures.
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*
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* Again, the data passed in should be the on-disk endian.
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*/
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int ocfs2_block_check_validate(void *data, size_t blocksize,
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struct ocfs2_block_check *bc,
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struct ocfs2_blockcheck_stats *stats)
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{
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int rc = 0;
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u32 bc_crc32e;
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u16 bc_ecc;
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u32 crc, ecc;
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ocfs2_blockcheck_inc_check(stats);
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bc_crc32e = le32_to_cpu(bc->bc_crc32e);
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bc_ecc = le16_to_cpu(bc->bc_ecc);
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memset(bc, 0, sizeof(struct ocfs2_block_check));
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/* Fast path - if the crc32 validates, we're good to go */
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crc = crc32_le(~0, data, blocksize);
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if (crc == bc_crc32e)
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goto out;
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ocfs2_blockcheck_inc_failure(stats);
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mlog(ML_ERROR,
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"CRC32 failed: stored: 0x%x, computed 0x%x. Applying ECC.\n",
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(unsigned int)bc_crc32e, (unsigned int)crc);
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/* Ok, try ECC fixups */
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ecc = ocfs2_hamming_encode_block(data, blocksize);
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ocfs2_hamming_fix_block(data, blocksize, ecc ^ bc_ecc);
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/* And check the crc32 again */
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crc = crc32_le(~0, data, blocksize);
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if (crc == bc_crc32e) {
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ocfs2_blockcheck_inc_recover(stats);
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goto out;
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}
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mlog(ML_ERROR, "Fixed CRC32 failed: stored: 0x%x, computed 0x%x\n",
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(unsigned int)bc_crc32e, (unsigned int)crc);
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rc = -EIO;
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out:
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bc->bc_crc32e = cpu_to_le32(bc_crc32e);
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bc->bc_ecc = cpu_to_le16(bc_ecc);
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return rc;
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}
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/*
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* This function generates check information for a list of buffer_heads.
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* bhs is the blocks to be checked. bc is a pointer to the
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* ocfs2_block_check structure describing the crc32 and the ecc.
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*
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* bc should be a pointer inside data, as the function will
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* take care of zeroing it before calculating the check information. If
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* bc does not point inside data, the caller must make sure any inline
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* ocfs2_block_check structures are zeroed.
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*
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* The data buffer must be in on-disk endian (little endian for ocfs2).
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* bc will be filled with little-endian values and will be ready to go to
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* disk.
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*/
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void ocfs2_block_check_compute_bhs(struct buffer_head **bhs, int nr,
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struct ocfs2_block_check *bc)
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{
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int i;
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u32 crc, ecc;
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BUG_ON(nr < 0);
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if (!nr)
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return;
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memset(bc, 0, sizeof(struct ocfs2_block_check));
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for (i = 0, crc = ~0, ecc = 0; i < nr; i++) {
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crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
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/*
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* The number of bits in a buffer is obviously b_size*8.
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* The offset of this buffer is b_size*i, so the bit offset
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* of this buffer is b_size*8*i.
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*/
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ecc = (u16)ocfs2_hamming_encode(ecc, bhs[i]->b_data,
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bhs[i]->b_size * 8,
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bhs[i]->b_size * 8 * i);
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}
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/*
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* No ecc'd ocfs2 structure is larger than 4K, so ecc will be no
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* larger than 16 bits.
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*/
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BUG_ON(ecc > USHRT_MAX);
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bc->bc_crc32e = cpu_to_le32(crc);
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bc->bc_ecc = cpu_to_le16((u16)ecc);
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}
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/*
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* This function validates existing check information on a list of
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* buffer_heads. Like _compute_bhs, the function will take care of
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* zeroing bc before calculating check codes. If bc is not a pointer
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* inside data, the caller must have zeroed any inline
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* ocfs2_block_check structures.
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*
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* Again, the data passed in should be the on-disk endian.
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*/
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int ocfs2_block_check_validate_bhs(struct buffer_head **bhs, int nr,
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struct ocfs2_block_check *bc,
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struct ocfs2_blockcheck_stats *stats)
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{
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int i, rc = 0;
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u32 bc_crc32e;
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u16 bc_ecc;
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u32 crc, ecc, fix;
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BUG_ON(nr < 0);
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if (!nr)
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return 0;
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ocfs2_blockcheck_inc_check(stats);
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bc_crc32e = le32_to_cpu(bc->bc_crc32e);
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bc_ecc = le16_to_cpu(bc->bc_ecc);
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memset(bc, 0, sizeof(struct ocfs2_block_check));
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/* Fast path - if the crc32 validates, we're good to go */
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for (i = 0, crc = ~0; i < nr; i++)
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crc = crc32_le(crc, bhs[i]->b_data, bhs[i]->b_size);
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if (crc == bc_crc32e)
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goto out;
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ocfs2_blockcheck_inc_failure(stats);
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mlog(ML_ERROR,
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"CRC32 failed: stored: %u, computed %u. Applying ECC.\n",
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(unsigned int)bc_crc32e, (unsigned int)crc);
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/* Ok, try ECC fixups */
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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 ^ 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 == bc_crc32e) {
|
|
ocfs2_blockcheck_inc_recover(stats);
|
|
goto out;
|
|
}
|
|
|
|
mlog(ML_ERROR, "Fixed CRC32 failed: stored: %u, computed %u\n",
|
|
(unsigned int)bc_crc32e, (unsigned int)crc);
|
|
|
|
rc = -EIO;
|
|
|
|
out:
|
|
bc->bc_crc32e = cpu_to_le32(bc_crc32e);
|
|
bc->bc_ecc = cpu_to_le16(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;
|
|
}
|
|
|