The existing CRC32c implementation uses Sarwate's algorithm to calculate the code one byte at a time. Using a slicing-by-8 algorithm adapted from Bob Pearson, we can process buffers 8 bytes at a time, for a substantial increase in performance. The motivation for this patchset is that I am working on adding full metadata checksumming to ext4 and jbd2. As far as performance impact of adding checksumming goes, I see nearly no change with a standard mail server ffsb simulation. On a test that involves only metadata operations (file creation and deletion, and fallocate/truncate), I see a drop of about 50 pcercent with the current kernel crc32c implementation; this improves to a drop of about 20 percent with the enclosed crc32c code. When metadata is usually a small fraction of total IO, this new implementation doesn't help much because metadata is usually a small fraction of total IO. However, when we are doing IO that is almost all metadata (such as rm -rf'ing a tree), then this patch speeds up the operation substantially. Given that iscsi, sctp, and btrfs also use crc32c, this patchset should improve their speed as well. I have some preliminary results[1] that show the difference in various crc algorithms that I've come across: the "crc32c-by8-le" column is the new algorithm in the patch; the "crc32c" column is the current crc32c kernel implementation; and the "crc32-kern-le" column is the current crc32 kernel implementation, which is similar to the results one gets for CONFIG_CRC32C_SLICEBY4=y. As you can see, the new implementation runs at nearly 4x the speed of the current implementation; even the slimmer slice-by-4 implementation is generally 2-3x faster. However, the implementation allows the kernel builder to select from a variety of space-speed tradeoffs, should my results not hold true on a particular class of system. v2: Use the crypto testmgr api for self-test. v3: Get rid of the -be version, which had no users. v4: Allow kernel builder a choice of speed vs. space optimization. [1]http://djwong.org/docs/ext4_metadata_checksums.html (cached copy of the ext4 wiki) Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> --- crypto/Kconfig | 36 +++++ crypto/Makefile | 11 ++ crypto/crc32c.c | 305 ++++++++++++++++++++++++++++++++++------------ crypto/crc32c_defs.h | 39 ++++++ crypto/gen_crc32ctable.c | 79 ++++++++++++ 5 files changed, 389 insertions(+), 81 deletions(-) create mode 100644 crypto/crc32c_defs.h create mode 100644 crypto/gen_crc32ctable.c diff --git a/crypto/Kconfig b/crypto/Kconfig index ae27b75..3fb6dc8 100644 --- a/crypto/Kconfig +++ b/crypto/Kconfig @@ -307,6 +307,42 @@ config CRYPTO_CRC32C by iSCSI for header and data digests and by others. See Castagnoli93. Module will be crc32c. +if CRYPTO_CRC32C +choice + prompt "CRC32C variant" + default CRC32C_SLICEBY8 + +config CRC32C_SLICEBY8 + bool "Slice by 8 bytes" + ---help--- + Calculate checksum 8 bytes at a time with a clever slicing algorithm. + This is the fastest algorithm, but comes with a 8KiB lookup table. + Most modern processors have sufficient cache that this shouldn't be + a huge problem. + + If you don't know which to choose, choose this one. + +config CRC32C_SLICEBY4 + bool "Slice by 4 bytes" + ---help--- + Calculate checksum 8 bytes at a time with a clever slicing algorithm. + This is reasonably fast, but has a 4KiB lookup table. + +config CRC32C_SARWATE + bool "Sarwate's Algorithm (one byte at a time)" + ---help--- + Calculate checksum a byte at a time using Sarwate's algorithm. This + is not very fast, but has a svelte 256 byte lookup table. + +config CRC32C_BIT + bool "Classic Algorithm (one bit at a time)" + ---help--- + Calculate checksum one bit at a time. This is VERY slow, but has + no lookup table. This is provided as a debugging option. + +endchoice +endif + config CRYPTO_CRC32C_INTEL tristate "CRC32c INTEL hardware acceleration" depends on X86 diff --git a/crypto/Makefile b/crypto/Makefile index ce5a813..00811ef 100644 --- a/crypto/Makefile +++ b/crypto/Makefile @@ -94,3 +94,14 @@ obj-$(CONFIG_CRYPTO_USER_API_SKCIPHER) += algif_skcipher.o # obj-$(CONFIG_XOR_BLOCKS) += xor.o obj-$(CONFIG_ASYNC_CORE) += async_tx/ + +hostprogs-y := gen_crc32ctable +clean-files := crc32ctable.h + +$(obj)/crc32c.o: $(obj)/crc32c_table.h + +quiet_cmd_crc32c = GEN $@ + cmd_crc32c = $< > $@ + +$(obj)/crc32c_table.h: $(obj)/gen_crc32ctable + $(call cmd,crc32c) diff --git a/crypto/crc32c.c b/crypto/crc32c.c index 3f9ad28..d510ec8 100644 --- a/crypto/crc32c.c +++ b/crypto/crc32c.c @@ -33,6 +33,35 @@ * Software Foundation; either version 2 of the License, or (at your option) * any later version. * + * The current crc32c implementation is adapted from Bob Pearson's slice-by-8 + * crc32 kernel patch from mid-2011. + * + * August 26, 2011 Darrick J. Wong <djwong at us.ibm.com> + * Reuse Bob Pearson's slice-by-8 implementation for e2fsprogs. + * + * July 20, 2011 Bob Pearson <rpearson at systemfabricworks.com> + * added slice by 8 algorithm to the existing conventional and + * slice by 4 algorithms. + * + * Oct 15, 2000 Matt Domsch <Matt_Domsch@xxxxxxxx> + * Nicer crc32 functions/docs submitted by linux@xxxxxxxxxxx. Thanks! + * Code was from the public domain, copyright abandoned. Code was + * subsequently included in the kernel, thus was re-licensed under the + * GNU GPL v2. + * + * Oct 12, 2000 Matt Domsch <Matt_Domsch@xxxxxxxx> + * Same crc32 function was used in 5 other places in the kernel. + * I made one version, and deleted the others. + * There are various incantations of crc32(). Some use a seed of 0 or ~0. + * Some xor at the end with ~0. The generic crc32() function takes + * seed as an argument, and doesn't xor at the end. Then individual + * users can do whatever they need. + * drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0. + * fs/jffs2 uses seed 0, doesn't xor with ~0. + * fs/partitions/efi.c uses seed ~0, xor's with ~0. + * + * This source code is licensed under the GNU General Public License, + * Version 2. See the file COPYING for more details. */ #include <crypto/internal/hash.h> @@ -40,6 +69,7 @@ #include <linux/module.h> #include <linux/string.h> #include <linux/kernel.h> +#include "crc32c_defs.h" #define CHKSUM_BLOCK_SIZE 1 #define CHKSUM_DIGEST_SIZE 4 @@ -52,92 +82,205 @@ struct chksum_desc_ctx { u32 crc; }; -/* - * This is the CRC-32C table - * Generated with: - * width = 32 bits - * poly = 0x1EDC6F41 - * reflect input bytes = true - * reflect output bytes = true - */ +#if CRC32C_BITS > 8 +# define tole(x) (__force u32) __constant_cpu_to_le32(x) +#else +# define tole(x) (x) +#endif -static const u32 crc32c_table[256] = { - 0x00000000L, 0xF26B8303L, 0xE13B70F7L, 0x1350F3F4L, - 0xC79A971FL, 0x35F1141CL, 0x26A1E7E8L, 0xD4CA64EBL, - 0x8AD958CFL, 0x78B2DBCCL, 0x6BE22838L, 0x9989AB3BL, - 0x4D43CFD0L, 0xBF284CD3L, 0xAC78BF27L, 0x5E133C24L, - 0x105EC76FL, 0xE235446CL, 0xF165B798L, 0x030E349BL, - 0xD7C45070L, 0x25AFD373L, 0x36FF2087L, 0xC494A384L, - 0x9A879FA0L, 0x68EC1CA3L, 0x7BBCEF57L, 0x89D76C54L, - 0x5D1D08BFL, 0xAF768BBCL, 0xBC267848L, 0x4E4DFB4BL, - 0x20BD8EDEL, 0xD2D60DDDL, 0xC186FE29L, 0x33ED7D2AL, - 0xE72719C1L, 0x154C9AC2L, 0x061C6936L, 0xF477EA35L, - 0xAA64D611L, 0x580F5512L, 0x4B5FA6E6L, 0xB93425E5L, - 0x6DFE410EL, 0x9F95C20DL, 0x8CC531F9L, 0x7EAEB2FAL, - 0x30E349B1L, 0xC288CAB2L, 0xD1D83946L, 0x23B3BA45L, - 0xF779DEAEL, 0x05125DADL, 0x1642AE59L, 0xE4292D5AL, - 0xBA3A117EL, 0x4851927DL, 0x5B016189L, 0xA96AE28AL, - 0x7DA08661L, 0x8FCB0562L, 0x9C9BF696L, 0x6EF07595L, - 0x417B1DBCL, 0xB3109EBFL, 0xA0406D4BL, 0x522BEE48L, - 0x86E18AA3L, 0x748A09A0L, 0x67DAFA54L, 0x95B17957L, - 0xCBA24573L, 0x39C9C670L, 0x2A993584L, 0xD8F2B687L, - 0x0C38D26CL, 0xFE53516FL, 0xED03A29BL, 0x1F682198L, - 0x5125DAD3L, 0xA34E59D0L, 0xB01EAA24L, 0x42752927L, - 0x96BF4DCCL, 0x64D4CECFL, 0x77843D3BL, 0x85EFBE38L, - 0xDBFC821CL, 0x2997011FL, 0x3AC7F2EBL, 0xC8AC71E8L, - 0x1C661503L, 0xEE0D9600L, 0xFD5D65F4L, 0x0F36E6F7L, - 0x61C69362L, 0x93AD1061L, 0x80FDE395L, 0x72966096L, - 0xA65C047DL, 0x5437877EL, 0x4767748AL, 0xB50CF789L, - 0xEB1FCBADL, 0x197448AEL, 0x0A24BB5AL, 0xF84F3859L, - 0x2C855CB2L, 0xDEEEDFB1L, 0xCDBE2C45L, 0x3FD5AF46L, - 0x7198540DL, 0x83F3D70EL, 0x90A324FAL, 0x62C8A7F9L, - 0xB602C312L, 0x44694011L, 0x5739B3E5L, 0xA55230E6L, - 0xFB410CC2L, 0x092A8FC1L, 0x1A7A7C35L, 0xE811FF36L, - 0x3CDB9BDDL, 0xCEB018DEL, 0xDDE0EB2AL, 0x2F8B6829L, - 0x82F63B78L, 0x709DB87BL, 0x63CD4B8FL, 0x91A6C88CL, - 0x456CAC67L, 0xB7072F64L, 0xA457DC90L, 0x563C5F93L, - 0x082F63B7L, 0xFA44E0B4L, 0xE9141340L, 0x1B7F9043L, - 0xCFB5F4A8L, 0x3DDE77ABL, 0x2E8E845FL, 0xDCE5075CL, - 0x92A8FC17L, 0x60C37F14L, 0x73938CE0L, 0x81F80FE3L, - 0x55326B08L, 0xA759E80BL, 0xB4091BFFL, 0x466298FCL, - 0x1871A4D8L, 0xEA1A27DBL, 0xF94AD42FL, 0x0B21572CL, - 0xDFEB33C7L, 0x2D80B0C4L, 0x3ED04330L, 0xCCBBC033L, - 0xA24BB5A6L, 0x502036A5L, 0x4370C551L, 0xB11B4652L, - 0x65D122B9L, 0x97BAA1BAL, 0x84EA524EL, 0x7681D14DL, - 0x2892ED69L, 0xDAF96E6AL, 0xC9A99D9EL, 0x3BC21E9DL, - 0xEF087A76L, 0x1D63F975L, 0x0E330A81L, 0xFC588982L, - 0xB21572C9L, 0x407EF1CAL, 0x532E023EL, 0xA145813DL, - 0x758FE5D6L, 0x87E466D5L, 0x94B49521L, 0x66DF1622L, - 0x38CC2A06L, 0xCAA7A905L, 0xD9F75AF1L, 0x2B9CD9F2L, - 0xFF56BD19L, 0x0D3D3E1AL, 0x1E6DCDEEL, 0xEC064EEDL, - 0xC38D26C4L, 0x31E6A5C7L, 0x22B65633L, 0xD0DDD530L, - 0x0417B1DBL, 0xF67C32D8L, 0xE52CC12CL, 0x1747422FL, - 0x49547E0BL, 0xBB3FFD08L, 0xA86F0EFCL, 0x5A048DFFL, - 0x8ECEE914L, 0x7CA56A17L, 0x6FF599E3L, 0x9D9E1AE0L, - 0xD3D3E1ABL, 0x21B862A8L, 0x32E8915CL, 0xC083125FL, - 0x144976B4L, 0xE622F5B7L, 0xF5720643L, 0x07198540L, - 0x590AB964L, 0xAB613A67L, 0xB831C993L, 0x4A5A4A90L, - 0x9E902E7BL, 0x6CFBAD78L, 0x7FAB5E8CL, 0x8DC0DD8FL, - 0xE330A81AL, 0x115B2B19L, 0x020BD8EDL, 0xF0605BEEL, - 0x24AA3F05L, 0xD6C1BC06L, 0xC5914FF2L, 0x37FACCF1L, - 0x69E9F0D5L, 0x9B8273D6L, 0x88D28022L, 0x7AB90321L, - 0xAE7367CAL, 0x5C18E4C9L, 0x4F48173DL, 0xBD23943EL, - 0xF36E6F75L, 0x0105EC76L, 0x12551F82L, 0xE03E9C81L, - 0x34F4F86AL, 0xC69F7B69L, 0xD5CF889DL, 0x27A40B9EL, - 0x79B737BAL, 0x8BDCB4B9L, 0x988C474DL, 0x6AE7C44EL, - 0xBE2DA0A5L, 0x4C4623A6L, 0x5F16D052L, 0xAD7D5351L -}; +#include "crc32c_table.h" -/* - * Steps through buffer one byte at at time, calculates reflected - * crc using table. - */ +#if CRC32C_BITS == 32 +/* slice by 4 algorithm */ +static u32 crc32c_body(u32 crc, u8 const *buf, size_t len) +{ + const u8 *p8; + const u32 *p32; + size_t init_bytes; + size_t words; + size_t end_bytes; + size_t i; + u32 q; + u8 i0, i1, i2, i3; + + crc = (__force u32) __cpu_to_le32(crc); + + /* unroll loop into 'init_bytes' odd bytes followed by + * 'words' aligned 4 byte words followed by + * 'end_bytes' odd bytes at the end */ + p8 = buf; + p32 = (u32 *)PTR_ALIGN(p8, 4); + init_bytes = min((uintptr_t)p32 - (uintptr_t)p8, len); + words = (len - init_bytes) >> 2; + end_bytes = (len - init_bytes) & 3; + + for (i = 0; i < init_bytes; i++) { +#ifdef __LITTLE_ENDIAN + i0 = *p8++ ^ crc; + crc = t0_le[i0] ^ (crc >> 8); +#else + i0 = *p8++ ^ (crc >> 24); + crc = t0_le[i0] ^ (crc << 8); +#endif + } + + /* using pre-increment below slightly faster */ + p32--; + + for (i = 0; i < words; i++) { +#ifdef __LITTLE_ENDIAN + q = *++p32 ^ crc; + i3 = q; + i2 = q >> 8; + i1 = q >> 16; + i0 = q >> 24; + crc = t3_le[i3] ^ t2_le[i2] ^ t1_le[i1] ^ t0_le[i0]; +#else + q = *++p32 ^ crc; + i3 = q >> 24; + i2 = q >> 16; + i1 = q >> 8; + i0 = q; + crc = t3_le[i3] ^ t2_le[i2] ^ t1_le[i1] ^ t0_le[i0]; +#endif + } + + p8 = (u8 *)(++p32); + + for (i = 0; i < end_bytes; i++) { +#ifdef __LITTLE_ENDIAN + i0 = *p8++ ^ crc; + crc = t0_le[i0] ^ (crc >> 8); +#else + i0 = *p8++ ^ (crc >> 24); + crc = t0_le[i0] ^ (crc << 8); +#endif + } -static u32 crc32c(u32 crc, const u8 *data, unsigned int length) + return __le32_to_cpu((__force __le32)crc); +} +#endif + +#if CRC32C_BITS == 64 +/* slice by 8 algorithm */ +static u32 crc32c_body(u32 crc, u8 const *buf, size_t len) { - while (length--) - crc = crc32c_table[(crc ^ *data++) & 0xFFL] ^ (crc >> 8); + const u8 *p8; + const u32 *p32; + size_t init_bytes; + size_t words; + size_t end_bytes; + size_t i; + u32 q; + u8 i0, i1, i2, i3; + + crc = (__force u32) __cpu_to_le32(crc); + + p8 = buf; + p32 = (u32 *)PTR_ALIGN(p8, 8); + i = (void *)p32 - (void *)p8; + init_bytes = min(i, len); + words = (len - init_bytes) >> 3; + end_bytes = (len - init_bytes) & 7; + + for (i = 0; i < init_bytes; i++) { +#ifdef __LITTLE_ENDIAN + i0 = *p8++ ^ crc; + crc = t0_le[i0] ^ (crc >> 8); +#else + i0 = *p8++ ^ (crc >> 24); + crc = t0_le[i0] ^ (crc << 8); +#endif + } + + p32--; + + for (i = 0; i < words; i++) { +#ifdef __LITTLE_ENDIAN + q = *++p32 ^ crc; + i3 = q; + i2 = q >> 8; + i1 = q >> 16; + i0 = q >> 24; + crc = t7_le[i3] ^ t6_le[i2] ^ t5_le[i1] ^ t4_le[i0]; + + q = *++p32; + i3 = q; + i2 = q >> 8; + i1 = q >> 16; + i0 = q >> 24; + crc ^= t3_le[i3] ^ t2_le[i2] ^ t1_le[i1] ^ t0_le[i0]; +#else + q = *++p32 ^ crc; + i3 = q >> 24; + i2 = q >> 16; + i1 = q >> 8; + i0 = q; + crc = t7_le[i3] ^ t6_le[i2] ^ t5_le[i1] ^ t4_le[i0]; + + q = *++p32; + i3 = q >> 24; + i2 = q >> 16; + i1 = q >> 8; + i0 = q; + crc ^= t3_le[i3] ^ t2_le[i2] ^ t1_le[i1] ^ t0_le[i0]; +#endif + } + p8 = (u8 *)(++p32); + + for (i = 0; i < end_bytes; i++) { +#ifdef __LITTLE_ENDIAN + i0 = *p8++ ^ crc; + crc = t0_le[i0] ^ (crc >> 8); +#else + i0 = *p8++ ^ (crc >> 24); + crc = t0_le[i0] ^ (crc << 8); +#endif + } + + return __le32_to_cpu(crc); +} +#endif + +/** + * crc32c() - Calculate bitwise little-endian CRC32c. + * @crc: seed value for computation. ~0 for ext4, sometimes 0 for + * other uses, or the previous crc32c value if computing incrementally. + * @p: pointer to buffer over which CRC is run + * @len: length of buffer @p + */ +static u32 crc32c(u32 crc, unsigned char const *p, size_t len) +{ +#if CRC32C_BITS == 1 + int i; + while (len--) { + crc ^= *p++; + for (i = 0; i < 8; i++) + crc = (crc >> 1) ^ ((crc & 1) ? CRC32C_POLY_LE : 0); + } +# elif CRC32C_BITS == 2 + while (len--) { + crc ^= *p++; + crc = (crc >> 2) ^ t0_le[crc & 0x03]; + crc = (crc >> 2) ^ t0_le[crc & 0x03]; + crc = (crc >> 2) ^ t0_le[crc & 0x03]; + crc = (crc >> 2) ^ t0_le[crc & 0x03]; + } +# elif CRC32C_BITS == 4 + while (len--) { + crc ^= *p++; + crc = (crc >> 4) ^ t0_le[crc & 0x0f]; + crc = (crc >> 4) ^ t0_le[crc & 0x0f]; + } +# elif CRC32C_BITS == 8 + while (len--) { + crc ^= *p++; + crc = (crc >> 8) ^ t0_le[crc & 0xff]; + } +# else + crc = crc32c_body(crc, p, len); +# endif return crc; } diff --git a/crypto/crc32c_defs.h b/crypto/crc32c_defs.h new file mode 100644 index 0000000..ea4480d --- /dev/null +++ b/crypto/crc32c_defs.h @@ -0,0 +1,39 @@ +#ifndef CRC32C_DEFS_H_ +#define CRC32C_DEFS_H_ + +/* + * This is the CRC32c polynomial, as outlined by Castagnoli. + * x^32+x^28+x^27+x^26+x^25+x^23+x^22+x^20+x^19+x^18+x^14+x^13+x^11+x^10+x^9+ + * x^8+x^6+x^0 + */ +#define CRC32C_POLY_LE 0x82F63B78 + +/* How many bits at a time to use. Valid values are 1, 2, 4, 8, 32 and 64. */ +/* For less performance-sensitive, use 4 */ +#ifdef CONFIG_CRC32C_SLICEBY8 +# define CRC32C_BITS 64 +#endif +#ifdef CONFIG_CRC32C_SLICEBY4 +# define CRC32C_BITS 32 +#endif +#ifdef CONFIG_CRC32C_SARWATE +# define CRC32C_BITS 8 +#endif +#ifdef CONFIG_CRC32C_BIT +# define CRC32C_BITS 1 +#endif + +#ifndef CRC32C_BITS +# define CRC32C_BITS 64 +#endif + +/* + * Little-endian CRC computation. Used with serial bit streams sent + * lsbit-first. Be sure to use cpu_to_le32() to append the computed CRC. + */ +#if CRC32C_BITS > 64 || CRC32C_BITS < 1 || CRC32C_BITS == 16 || \ + CRC32C_BITS & CRC32C_BITS-1 +# error "CRC32C_BITS must be one of {1, 2, 4, 8, 32, 64}" +#endif + +#endif /* CRC32C_DEFS_H_ */ diff --git a/crypto/gen_crc32ctable.c b/crypto/gen_crc32ctable.c new file mode 100644 index 0000000..1715229 --- /dev/null +++ b/crypto/gen_crc32ctable.c @@ -0,0 +1,79 @@ +#include <stdio.h> +#include "crc32c_defs.h" +#include <inttypes.h> + +#define ENTRIES_PER_LINE 4 + +#if CRC32C_BITS <= 8 +#define LE_TABLE_SIZE (1 << CRC32C_BITS) +#else +#define LE_TABLE_SIZE 256 +#endif + +static uint32_t crc32c_table[8][256]; + +/** + * crc32c_init() - allocate and initialize LE table data + * + * crc is the crc of the byte i; other entries are filled in based on the + * fact that crctable[i^j] = crctable[i] ^ crctable[j]. + * + */ +static void crc32c_init(void) +{ + unsigned i, j; + uint32_t crc = 1; + + crc32c_table[0][0] = 0; + + for (i = LE_TABLE_SIZE >> 1; i; i >>= 1) { + crc = (crc >> 1) ^ ((crc & 1) ? CRC32C_POLY_LE : 0); + for (j = 0; j < LE_TABLE_SIZE; j += 2 * i) + crc32c_table[0][i + j] = crc ^ crc32c_table[0][j]; + } + for (i = 0; i < LE_TABLE_SIZE; i++) { + crc = crc32c_table[0][i]; + for (j = 1; j < 8; j++) { + crc = crc32c_table[0][crc & 0xff] ^ (crc >> 8); + crc32c_table[j][i] = crc; + } + } +} + +static void output_table(uint32_t table[8][256], int len, char trans) +{ + int i, j; + + for (j = 0 ; j < 8; j++) { + printf("static const u32 t%d_%ce[] = {", j, trans); + for (i = 0; i < len - 1; i++) { + if ((i % ENTRIES_PER_LINE) == 0) + printf("\n"); + printf("to%ce(0x%8.8xL),", trans, table[j][i]); + if ((i % ENTRIES_PER_LINE) != (ENTRIES_PER_LINE - 1)) + printf(" "); + } + printf("to%ce(0x%8.8xL)};\n\n", trans, table[j][len - 1]); + + if ((j+1)*8 >= CRC32C_BITS) + break; + } +} + +int main(int argc, char **argv) +{ + printf("/*\n"); + printf(" * crc32c_table.h - CRC32c tables\n"); + printf(" * this file is generated - do not edit\n"); + printf(" * # gen_crc32ctable > crc32c_table.h\n"); + printf(" * with\n"); + printf(" * CRC32C_BITS = %d\n", CRC32C_BITS); + printf(" */\n"); + + if (CRC32C_BITS > 1) { + crc32c_init(); + output_table(crc32c_table, LE_TABLE_SIZE, 'l'); + } + + return 0; +} -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
