diff options
Diffstat (limited to 'fs/ocfs2')
-rw-r--r-- | fs/ocfs2/blockcheck.c | 67 |
1 files changed, 20 insertions, 47 deletions
diff --git a/fs/ocfs2/blockcheck.c b/fs/ocfs2/blockcheck.c index 2ce6ae5e4b8c..1d5083cef3a2 100644 --- a/fs/ocfs2/blockcheck.c +++ b/fs/ocfs2/blockcheck.c | |||
@@ -31,7 +31,6 @@ | |||
31 | #include "blockcheck.h" | 31 | #include "blockcheck.h" |
32 | 32 | ||
33 | 33 | ||
34 | |||
35 | /* | 34 | /* |
36 | * We use the following conventions: | 35 | * We use the following conventions: |
37 | * | 36 | * |
@@ -39,26 +38,6 @@ | |||
39 | * p = # parity bits | 38 | * p = # parity bits |
40 | * c = # total code bits (d + p) | 39 | * c = # total code bits (d + p) |
41 | */ | 40 | */ |
42 | static int calc_parity_bits(unsigned int d) | ||
43 | { | ||
44 | unsigned int p; | ||
45 | |||
46 | /* | ||
47 | * Bits required for Single Error Correction is as follows: | ||
48 | * | ||
49 | * d + p + 1 <= 2^p | ||
50 | * | ||
51 | * We're restricting ourselves to 31 bits of parity, that should be | ||
52 | * sufficient. | ||
53 | */ | ||
54 | for (p = 1; p < 32; p++) | ||
55 | { | ||
56 | if ((d + p + 1) <= (1 << p)) | ||
57 | return p; | ||
58 | } | ||
59 | |||
60 | return 0; | ||
61 | } | ||
62 | 41 | ||
63 | /* | 42 | /* |
64 | * Calculate the bit offset in the hamming code buffer based on the bit's | 43 | * Calculate the bit offset in the hamming code buffer based on the bit's |
@@ -109,10 +88,9 @@ static unsigned int calc_code_bit(unsigned int i) | |||
109 | */ | 88 | */ |
110 | u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr) | 89 | u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr) |
111 | { | 90 | { |
112 | unsigned int p = calc_parity_bits(nr + d); | 91 | unsigned int i, b; |
113 | unsigned int i, j, b; | ||
114 | 92 | ||
115 | BUG_ON(!p); | 93 | BUG_ON(!d); |
116 | 94 | ||
117 | /* | 95 | /* |
118 | * b is the hamming code bit number. Hamming code specifies a | 96 | * b is the hamming code bit number. Hamming code specifies a |
@@ -131,27 +109,23 @@ u32 ocfs2_hamming_encode(u32 parity, void *data, unsigned int d, unsigned int nr | |||
131 | */ | 109 | */ |
132 | b = calc_code_bit(nr + i); | 110 | b = calc_code_bit(nr + i); |
133 | 111 | ||
134 | for (j = 0; j < p; j++) | 112 | /* |
135 | { | 113 | * Data bits in the resultant code are checked by |
136 | /* | 114 | * parity bits that are part of the bit number |
137 | * Data bits in the resultant code are checked by | 115 | * representation. Huh? |
138 | * parity bits that are part of the bit number | 116 | * |
139 | * representation. Huh? | 117 | * <wikipedia href="http://en.wikipedia.org/wiki/Hamming_code"> |
140 | * | 118 | * In other words, the parity bit at position 2^k |
141 | * <wikipedia href="http://en.wikipedia.org/wiki/Hamming_code"> | 119 | * checks bits in positions having bit k set in |
142 | * In other words, the parity bit at position 2^k | 120 | * their binary representation. Conversely, for |
143 | * checks bits in positions having bit k set in | 121 | * instance, bit 13, i.e. 1101(2), is checked by |
144 | * their binary representation. Conversely, for | 122 | * bits 1000(2) = 8, 0100(2)=4 and 0001(2) = 1. |
145 | * instance, bit 13, i.e. 1101(2), is checked by | 123 | * </wikipedia> |
146 | * bits 1000(2) = 8, 0100(2)=4 and 0001(2) = 1. | 124 | * |
147 | * </wikipedia> | 125 | * Note that 'k' is the _code_ bit number. 'b' in |
148 | * | 126 | * our loop. |
149 | * Note that 'k' is the _code_ bit number. 'b' in | 127 | */ |
150 | * our loop. | 128 | parity ^= b; |
151 | */ | ||
152 | if (b & (1 << j)) | ||
153 | parity ^= (1 << j); | ||
154 | } | ||
155 | } | 129 | } |
156 | 130 | ||
157 | /* While the data buffer was treated as little endian, the | 131 | /* While the data buffer was treated as little endian, the |
@@ -174,10 +148,9 @@ u32 ocfs2_hamming_encode_block(void *data, unsigned int blocksize) | |||
174 | void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr, | 148 | void ocfs2_hamming_fix(void *data, unsigned int d, unsigned int nr, |
175 | unsigned int fix) | 149 | unsigned int fix) |
176 | { | 150 | { |
177 | unsigned int p = calc_parity_bits(nr + d); | ||
178 | unsigned int i, b; | 151 | unsigned int i, b; |
179 | 152 | ||
180 | BUG_ON(!p); | 153 | BUG_ON(!d); |
181 | 154 | ||
182 | /* | 155 | /* |
183 | * If the bit to fix has an hweight of 1, it's a parity bit. One | 156 | * If the bit to fix has an hweight of 1, it's a parity bit. One |