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d352ac6814
This improves the comments at the top of many functions. It didn't dive into the guts of functions because I was trying to avoid merging problems with the new allocator and back reference work. extent-tree.c and volumes.c were both skipped, and there is definitely more work todo in cleaning and commenting the code. Signed-off-by: Chris Mason <chris.mason@oracle.com>
121 lines
3.0 KiB
C
121 lines
3.0 KiB
C
/*
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* Copyright (C) 2008 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#ifndef __BTRFS_CRC32C__
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#define __BTRFS_CRC32C__
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#include <asm/byteorder.h>
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#include <linux/crc32c.h>
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#include <linux/version.h>
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/* #define CONFIG_BTRFS_HW_SUM 1 */
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#ifdef CONFIG_BTRFS_HW_SUM
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#ifdef CONFIG_X86
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/*
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* Using hardware provided CRC32 instruction to accelerate the CRC32 disposal.
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* CRC32C polynomial:0x1EDC6F41(BE)/0x82F63B78(LE)
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* CRC32 is a new instruction in Intel SSE4.2, the reference can be found at:
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* http://www.intel.com/products/processor/manuals/
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* Intel(R) 64 and IA-32 Architectures Software Developer's Manual
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* Volume 2A: Instruction Set Reference, A-M
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*/
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#include <asm/cpufeature.h>
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#include <asm/processor.h>
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#define X86_FEATURE_XMM4_2 (4*32+20) /* Streaming SIMD Extensions-4.2 */
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#define cpu_has_xmm4_2 boot_cpu_has(X86_FEATURE_XMM4_2)
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#ifdef CONFIG_X86_64
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#define REX_PRE "0x48, "
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#define SCALE_F 8
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#else
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#define REX_PRE
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#define SCALE_F 4
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#endif
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static inline u32 btrfs_crc32c_le_hw_byte(u32 crc, unsigned char const *data,
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size_t length)
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{
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while (length--) {
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__asm__ __volatile__(
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".byte 0xf2, 0xf, 0x38, 0xf0, 0xf1"
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:"=S"(crc)
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:"0"(crc), "c"(*data)
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);
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data++;
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}
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return crc;
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}
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static inline u32 __pure btrfs_crc32c_le_hw(u32 crc, unsigned char const *p,
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size_t len)
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{
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unsigned int iquotient = len / SCALE_F;
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unsigned int iremainder = len % SCALE_F;
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#ifdef CONFIG_X86_64
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u64 *ptmp = (u64 *)p;
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#else
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u32 *ptmp = (u32 *)p;
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#endif
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while (iquotient--) {
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__asm__ __volatile__(
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".byte 0xf2, " REX_PRE "0xf, 0x38, 0xf1, 0xf1;"
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:"=S"(crc)
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:"0"(crc), "c"(*ptmp)
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);
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ptmp++;
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}
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if (iremainder)
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crc = btrfs_crc32c_le_hw_byte(crc, (unsigned char *)ptmp,
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iremainder);
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return crc;
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}
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#endif /* CONFIG_BTRFS_HW_SUM */
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static inline u32 __btrfs_crc32c(u32 crc, unsigned char const *address,
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size_t len)
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{
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#ifdef CONFIG_BTRFS_HW_SUM
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if (cpu_has_xmm4_2)
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return btrfs_crc32c_le_hw(crc, address, len);
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#endif
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return crc32c_le(crc, address, len);
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}
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#else
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#define __btrfs_crc32c(seed, data, length) crc32c(seed, data, length)
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#endif /* CONFIG_X86 */
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/**
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* implementation of crc32c_le() changed in linux-2.6.23,
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* has of v0.13 btrfs-progs is using the latest version.
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* We must workaround older implementations of crc32c_le()
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* found on older kernel versions.
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*/
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#define btrfs_crc32c(seed, data, length) \
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__btrfs_crc32c(seed, (unsigned char const *)data, length)
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#endif
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