[PATCH 2/4] btrfs: add LZ4 compression method

[David Sterba <dsterba@suse.cz>]

Adjusted a few defines to compile. The on-stack context allocation is
disabled and either LZ4_compress64kCtx or LZ4_compressCtx must be used.

Origin: http://lz4.googlecode.com/svn/trunk
Revision: 55

Signed-off-by: David Sterba <dsterba@suse.cz>
---
 fs/btrfs/Makefile |    2 +-
 fs/btrfs/lz4.c    |  810 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/lz4.h    |  107 +++++++
 3 files changed, 918 insertions(+), 1 deletions(-)
 create mode 100644 fs/btrfs/lz4.c
 create mode 100644 fs/btrfs/lz4.h

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index f22fe03..11f8c4e 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -8,7 +8,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
 	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
 	   export.o tree-log.o free-space-cache.o zlib.o lzo.o \
 	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
-	   reada.o backref.o ulist.o snappy.o
+	   reada.o backref.o ulist.o snappy.o lz4.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
diff --git a/fs/btrfs/lz4.c b/fs/btrfs/lz4.c
new file mode 100644
index 0000000..e41d0cf
--- /dev/null
+++ b/fs/btrfs/lz4.c
@@ -0,0 +1,810 @@
+/*
+   LZ4 - Fast LZ compression algorithm
+   Copyright (C) 2011-2012, Yann Collet.
+   BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
+
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions are
+   met:
+
+       * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+       * Redistributions in binary form must reproduce the above
+   copyright notice, this list of conditions and the following disclaimer
+   in the documentation and/or other materials provided with the
+   distribution.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+/*
+ * With authors permission dual licensed as BSD/GPL for linux kernel
+ *
+ * Origin: http://lz4.googlecode.com/svn/trunk
+ * Revision: 55
+ */
+
+//**************************************
+// Tuning parameters
+//**************************************
+// COMPRESSIONLEVEL :
+// Increasing this value improves compression ratio
+// Lowering this value reduces memory usage
+// Reduced memory usage typically improves speed, due to cache effect (ex : L1 32KB for Intel, L1 64KB for AMD)
+// Memory usage formula : N->2^(N+2) Bytes (examples : 12 -> 16KB ; 17 -> 512KB)
+#define COMPRESSIONLEVEL 12
+
+// NONCOMPRESSIBLE_CONFIRMATION :
+// Decreasing this value will make the algorithm skip faster data segments considered "incompressible"
+// This may decrease compression ratio dramatically, but will be faster on incompressible data
+// Increasing this value will make the algorithm search more before declaring a segment "incompressible"
+// This could improve compression a bit, but will be slower on incompressible data
+// The default value (6) is recommended
+#define NONCOMPRESSIBLE_CONFIRMATION 6
+
+// BIG_ENDIAN_NATIVE_BUT_INCOMPATIBLE :
+// This will provide a boost to performance for big endian cpu, but the resulting compressed stream will be incompatible with little-endian CPU.
+// You can set this option to 1 in situations where data will stay within closed environment
+// This option is useless on Little_Endian CPU (such as x86)
+//#define BIG_ENDIAN_NATIVE_BUT_INCOMPATIBLE 1
+
+
+
+//**************************************
+// CPU Feature Detection
+//**************************************
+// 32 or 64 bits ?
+#if (__x86_64__ || __x86_64 || __amd64__ || __amd64 || __ppc64__ || _WIN64 || __LP64__ || _LP64)   // Detects 64 bits mode
+#define ARCH64 1
+#else
+#define ARCH64 0
+#endif
+
+// Little Endian or Big Endian ? 
+#if (__BIG_ENDIAN__ || __BIG_ENDIAN || _BIG_ENDIAN || _ARCH_PPC || __PPC__ || __PPC || PPC || __powerpc__ || __powerpc || powerpc || ((defined(__BYTE_ORDER__)&&(__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__))) )
+#define CPU_BIG_ENDIAN 1
+#else
+// Little Endian assumed. PDP Endian and other very rare endian format are unsupported.
+#endif
+
+// Unaligned memory access ?
+// This feature is automatically enabled for "common" CPU, such as x86.
+// For others CPU, you may want to force this option manually to improve performance if your target CPU supports unaligned memory access
+#if (__ARM_FEATURE_UNALIGNED)
+#define CPU_UNALIGNED_ACCESS 1
+#endif
+
+// Uncomment this parameter if your target system does not support hardware bit count
+//#define _FORCE_SW_BITCOUNT
+
+
+
+//**************************************
+// Compiler Options
+//**************************************
+#if __STDC_VERSION__ >= 199901L    // C99
+  /* "restrict" is a known keyword */
+#else
+#define restrict  // Disable restrict
+#endif
+
+#ifdef _MSC_VER
+#define inline __forceinline    // Visual is not C99, but supports inline
+#endif
+
+#if (defined(__GNUC__) && (!(CPU_UNALIGNED_ACCESS)))
+#define _PACKED __attribute__ ((packed))
+#else
+#define _PACKED
+#endif
+
+#ifdef _MSC_VER  // Visual Studio
+#define bswap16(i) _byteswap_ushort(i)
+#else
+#define bswap16(i) (((i)>>8) | ((i)<<8))
+#endif
+
+
+//**************************************
+// Includes
+//**************************************
+#ifdef __KERNEL__
+#include <linux/string.h>
+#include <linux/bug.h>
+#define malloc(size)	({ BUG(); (void*)0; })
+#define free(ptr)	({ BUG(); (void*)0; })
+#else
+#include <stdlib.h>   // for malloc
+#include <string.h>   // for memset
+#include "lz4.h"
+#endif
+
+
+//**************************************
+// Basic Types
+//**************************************
+#if defined(_MSC_VER)    // Visual Studio does not support 'stdint' natively
+#define BYTE	unsigned __int8
+#define U16		unsigned __int16
+#define U32		unsigned __int32
+#define S32		__int32
+#define U64		unsigned __int64
+#else
+#ifdef __KERNEL__
+#include <asm/byteorder.h>
+#include <linux/types.h>
+#define BYTE	u8
+#define U16	u16
+#define U32	u32
+#define S32	s32
+#define U64	u64
+
+#else
+#include <stdint.h>
+#define BYTE	uint8_t
+#define U16		uint16_t
+#define U32		uint32_t
+#define S32		int32_t
+#define U64		uint64_t
+#endif // __KERNEL__
+#endif
+
+
+//**************************************
+// Constants
+//**************************************
+#define MINMATCH 4
+#define SKIPSTRENGTH (NONCOMPRESSIBLE_CONFIRMATION>2?NONCOMPRESSIBLE_CONFIRMATION:2)
+#define STACKLIMIT 13
+#define HEAPMODE (HASH_LOG>STACKLIMIT)  // Defines if memory is allocated into the stack (local variable), or into the heap (malloc()).
+#define COPYLENGTH 8
+#define LASTLITERALS 5
+#define MFLIMIT (COPYLENGTH+MINMATCH)
+#define MINLENGTH (MFLIMIT+1)
+
+#define MAXD_LOG 16
+#define MAX_DISTANCE ((1 << MAXD_LOG) - 1)
+
+#define HASH_LOG COMPRESSIONLEVEL
+#define HASHTABLESIZE (1 << HASH_LOG)
+#define HASH_MASK (HASHTABLESIZE - 1)
+
+#define ML_BITS 4
+#define ML_MASK ((1U<<ML_BITS)-1)
+#define RUN_BITS (8-ML_BITS)
+#define RUN_MASK ((1U<<RUN_BITS)-1)
+
+/*
+ * Disable on-stack context allocation for linux kernel
+ */
+#undef STACKLIMIT
+#define STACKLIMIT 0
+
+
+//**************************************
+// Architecture-specific macros
+//**************************************
+#if ARCH64	// 64-bit
+#define STEPSIZE 8
+#define UARCH U64
+#define AARCH A64
+#define LZ4_COPYSTEP(s,d)		A64(d) = A64(s); d+=8; s+=8;
+#define LZ4_COPYPACKET(s,d)		LZ4_COPYSTEP(s,d)
+#define LZ4_SECURECOPY(s,d,e)	if (d<e) LZ4_WILDCOPY(s,d,e)
+#define HTYPE U32
+#define INITBASE(base)			const BYTE* const base = ip
+#else		// 32-bit
+#define STEPSIZE 4
+#define UARCH U32
+#define AARCH A32
+#define LZ4_COPYSTEP(s,d)		A32(d) = A32(s); d+=4; s+=4;
+#define LZ4_COPYPACKET(s,d)		LZ4_COPYSTEP(s,d); LZ4_COPYSTEP(s,d);
+#define LZ4_SECURECOPY			LZ4_WILDCOPY
+#define HTYPE const BYTE*
+#define INITBASE(base)			const int base = 0
+#endif
+
+#if ((CPU_BIG_ENDIAN) && !(BIG_ENDIAN_NATIVE_BUT_INCOMPATIBLE))
+#define LZ4_READ_LITTLEENDIAN_16(d,s,p) { U16 v = A16(p); v = bswap16(v); d = (s) - v; }
+#define LZ4_WRITE_LITTLEENDIAN_16(p,i) { U16 v = (U16)(i); v = bswap16(v); A16(p) = v; p+=2; }
+#else		// Little Endian
+#define LZ4_READ_LITTLEENDIAN_16(d,s,p) { d = (s) - A16(p); }
+#define LZ4_WRITE_LITTLEENDIAN_16(p,v) { A16(p) = v; p+=2; }
+#endif
+
+
+//**************************************
+// Local structures
+//**************************************
+struct refTables
+{
+	HTYPE hashTable[HASHTABLESIZE];
+};
+
+typedef struct _U64_S
+{
+	U64 v;
+} _PACKED U64_S;
+
+typedef struct _U32_S
+{
+	U32 v;
+} _PACKED U32_S;
+
+typedef struct _U16_S
+{
+	U16 v;
+} _PACKED U16_S;
+
+#define A64(x) (((U64_S *)(x))->v)
+#define A32(x) (((U32_S *)(x))->v)
+#define A16(x) (((U16_S *)(x))->v)
+
+
+//**************************************
+// Macros
+//**************************************
+#define LZ4_HASH_FUNCTION(i)	(((i) * 2654435761U) >> ((MINMATCH*8)-HASH_LOG))
+#define LZ4_HASH_VALUE(p)		LZ4_HASH_FUNCTION(A32(p))
+#define LZ4_WILDCOPY(s,d,e)		do { LZ4_COPYPACKET(s,d) } while (d<e);
+#define LZ4_BLINDCOPY(s,d,l)	{ BYTE* e=(d)+l; LZ4_WILDCOPY(s,d,e); d=e; }
+
+
+//****************************
+// Private functions
+//****************************
+#if ARCH64
+
+inline static int LZ4_NbCommonBytes (register U64 val)
+{
+#if CPU_BIG_ENDIAN
+    #if defined(_MSC_VER) && !defined(_FORCE_SW_BITCOUNT)
+    unsigned long r = 0;
+    _BitScanReverse64( &r, val );
+    return (int)(r>>3);
+    #elif defined(__GNUC__) && !defined(_FORCE_SW_BITCOUNT)
+    return (__builtin_clzll(val) >> 3);
+    #else
+	int r;
+	if (!(val>>32)) { r=4; } else { r=0; val>>=32; }
+	if (!(val>>16)) { r+=2; val>>=8; } else { val>>=24; }
+	r += (!val);
+	return r;
+    #endif
+#else
+    #if defined(_MSC_VER) && !defined(_FORCE_SW_BITCOUNT)
+    unsigned long r = 0;
+    _BitScanForward64( &r, val );
+    return (int)(r>>3);
+    #elif defined(__GNUC__) && !defined(_FORCE_SW_BITCOUNT)
+    return (__builtin_ctzll(val) >> 3); 
+    #else
+	static const int DeBruijnBytePos[64] = { 0, 0, 0, 0, 0, 1, 1, 2, 0, 3, 1, 3, 1, 4, 2, 7, 0, 2, 3, 6, 1, 5, 3, 5, 1, 3, 4, 4, 2, 5, 6, 7, 7, 0, 1, 2, 3, 3, 4, 6, 2, 6, 5, 5, 3, 4, 5, 6, 7, 1, 2, 4, 6, 4, 4, 5, 7, 2, 6, 5, 7, 6, 7, 7 };
+	return DeBruijnBytePos[((U64)((val & -val) * 0x0218A392CDABBD3F)) >> 58];
+    #endif
+#endif
+}
+
+#else
+
+inline static int LZ4_NbCommonBytes (register U32 val)
+{
+#if CPU_BIG_ENDIAN
+    #if defined(_MSC_VER) && !defined(_FORCE_SW_BITCOUNT)
+    unsigned long r = 0;
+    _BitScanReverse( &r, val );
+    return (int)(r>>3);
+    #elif defined(__GNUC__) && !defined(_FORCE_SW_BITCOUNT)
+    return (__builtin_clz(val) >> 3);
+    #else
+	int r;
+	if (!(val>>16)) { r=2; val>>=8; } else { r=0; val>>=24; }
+	r += (!val);
+	return r;
+    #endif
+#else
+    #if defined(_MSC_VER) && !defined(_FORCE_SW_BITCOUNT)
+    unsigned long r = 0;
+    _BitScanForward( &r, val );
+    return (int)(r>>3);
+    #elif defined(__GNUC__) && !defined(_FORCE_SW_BITCOUNT)
+    return (__builtin_ctz(val) >> 3); 
+    #else
+	static const int DeBruijnBytePos[32] = { 0, 0, 3, 0, 3, 1, 3, 0, 3, 2, 2, 1, 3, 2, 0, 1, 3, 3, 1, 2, 2, 2, 2, 0, 3, 1, 2, 0, 1, 0, 1, 1 };
+	return DeBruijnBytePos[((U32)((val & -val) * 0x077CB531U)) >> 27];
+    #endif
+#endif
+}
+
+#endif
+
+
+//******************************
+// Public Compression functions
+//******************************
+
+int LZ4_compressCtx(void** ctx,
+				 const char* source,
+				 char* dest,
+				 int isize)
+{
+#if HEAPMODE
+	struct refTables *srt = (struct refTables *) (*ctx);
+	HTYPE* HashTable;
+#else
+	HTYPE HashTable[HASHTABLESIZE] = {0};
+#endif
+
+	const BYTE* ip = (BYTE*) source;
+	INITBASE(base);
+	const BYTE* anchor = ip;
+	const BYTE* const iend = ip + isize;
+	const BYTE* const mflimit = iend - MFLIMIT;
+#define matchlimit (iend - LASTLITERALS)
+
+	BYTE* op = (BYTE*) dest;
+
+	int len, length;
+	const int skipStrength = SKIPSTRENGTH;
+	U32 forwardH;
+
+
+	// Init
+	if (isize<MINLENGTH) goto _last_literals;
+#if HEAPMODE
+	if (*ctx == NULL)
+	{
+		srt = (struct refTables *) malloc ( sizeof(struct refTables) );
+		*ctx = (void*) srt;
+	}
+	HashTable = (HTYPE*)(srt->hashTable);
+	memset((void*)HashTable, 0, sizeof(srt->hashTable));
+#else
+	(void) ctx;
+#endif
+
+
+	// First Byte
+	HashTable[LZ4_HASH_VALUE(ip)] = ip - base;
+	ip++; forwardH = LZ4_HASH_VALUE(ip);
+
+	// Main Loop
+    for ( ; ; )
+	{
+		int findMatchAttempts = (1U << skipStrength) + 3;
+		const BYTE* forwardIp = ip;
+		const BYTE* ref;
+		BYTE* token;
+
+		// Find a match
+		do {
+			U32 h = forwardH;
+			int step = findMatchAttempts++ >> skipStrength;
+			ip = forwardIp;
+			forwardIp = ip + step;
+
+			if (forwardIp > mflimit) { goto _last_literals; }
+
+			forwardH = LZ4_HASH_VALUE(forwardIp);
+			ref = base + HashTable[h];
+			HashTable[h] = ip - base;
+
+		} while ((ref < ip - MAX_DISTANCE) || (A32(ref) != A32(ip)));
+
+		// Catch up
+		while ((ip>anchor) && (ref>(BYTE*)source) && (ip[-1]==ref[-1])) { ip--; ref--; }
+
+		// Encode Literal length
+		length = ip - anchor;
+		token = op++;
+		if (length>=(int)RUN_MASK) { *token=(RUN_MASK<<ML_BITS); len = length-RUN_MASK; for(; len > 254 ; len-=255) *op++ = 255; *op++ = (BYTE)len; }
+		else *token = (length<<ML_BITS);
+
+		// Copy Literals
+		LZ4_BLINDCOPY(anchor, op, length);
+
+_next_match:
+		// Encode Offset
+		LZ4_WRITE_LITTLEENDIAN_16(op,ip-ref);
+
+		// Start Counting
+		ip+=MINMATCH; ref+=MINMATCH;   // MinMatch verified
+		anchor = ip;
+		while (ip<matchlimit-(STEPSIZE-1))
+		{
+			UARCH diff = AARCH(ref) ^ AARCH(ip);
+			if (!diff) { ip+=STEPSIZE; ref+=STEPSIZE; continue; }
+			ip += LZ4_NbCommonBytes(diff);
+			goto _endCount;
+		}
+		if (ARCH64) if ((ip<(matchlimit-3)) && (A32(ref) == A32(ip))) { ip+=4; ref+=4; }
+		if ((ip<(matchlimit-1)) && (A16(ref) == A16(ip))) { ip+=2; ref+=2; }
+		if ((ip<matchlimit) && (*ref == *ip)) ip++;
+_endCount:
+
+		// Encode MatchLength
+		len = (ip - anchor);
+		if (len>=(int)ML_MASK) { *token+=ML_MASK; len-=ML_MASK; for(; len > 509 ; len-=510) { *op++ = 255; *op++ = 255; } if (len > 254) { len-=255; *op++ = 255; } *op++ = (BYTE)len; }
+		else *token += len;
+
+		// Test end of chunk
+		if (ip > mflimit) { anchor = ip;  break; }
+
+		// Fill table
+		HashTable[LZ4_HASH_VALUE(ip-2)] = ip - 2 - base;
+
+		// Test next position
+		ref = base + HashTable[LZ4_HASH_VALUE(ip)];
+		HashTable[LZ4_HASH_VALUE(ip)] = ip - base;
+		if ((ref > ip - (MAX_DISTANCE + 1)) && (A32(ref) == A32(ip))) { token = op++; *token=0; goto _next_match; }
+
+		// Prepare next loop
+		anchor = ip++;
+		forwardH = LZ4_HASH_VALUE(ip);
+	}
+
+_last_literals:
+	// Encode Last Literals
+	{
+		int lastRun = iend - anchor;
+		if (lastRun>=(int)RUN_MASK) { *op++=(RUN_MASK<<ML_BITS); lastRun-=RUN_MASK; for(; lastRun > 254 ; lastRun-=255) *op++ = 255; *op++ = (BYTE) lastRun; }
+		else *op++ = (lastRun<<ML_BITS);
+		memcpy(op, anchor, iend - anchor);
+		op += iend-anchor;
+	}
+
+	// End
+	return (int) (((char*)op)-dest);
+}
+
+
+
+// Note : this function is valid only if isize < LZ4_64KLIMIT
+#define LZ4_64KLIMIT ((1<<16) + (MFLIMIT-1))
+#define HASHLOG64K (HASH_LOG+1)
+#define HASH64KTABLESIZE (1U<<HASHLOG64K)
+#define LZ4_HASH64K_FUNCTION(i)	(((i) * 2654435761U) >> ((MINMATCH*8)-HASHLOG64K))
+#define LZ4_HASH64K_VALUE(p)	LZ4_HASH64K_FUNCTION(A32(p))
+int LZ4_compress64kCtx(void** ctx,
+				 const char* source,
+				 char* dest,
+				 int isize)
+{
+#if HEAPMODE
+	struct refTables *srt = (struct refTables *) (*ctx);
+	U16* HashTable;
+#else
+	U16 HashTable[HASH64KTABLESIZE] = {0};
+#endif
+
+	const BYTE* ip = (BYTE*) source;
+	const BYTE* anchor = ip;
+	const BYTE* const base = ip;
+	const BYTE* const iend = ip + isize;
+	const BYTE* const mflimit = iend - MFLIMIT;
+#define matchlimit (iend - LASTLITERALS)
+
+	BYTE* op = (BYTE*) dest;
+
+	int len, length;
+	const int skipStrength = SKIPSTRENGTH;
+	U32 forwardH;
+
+
+	// Init
+	if (isize<MINLENGTH) goto _last_literals;
+#if HEAPMODE
+	if (*ctx == NULL)
+	{
+		srt = (struct refTables *) malloc ( sizeof(struct refTables) );
+		*ctx = (void*) srt;
+	}
+	HashTable = (U16*)(srt->hashTable);
+	memset((void*)HashTable, 0, sizeof(srt->hashTable));
+#else
+	(void) ctx;
+#endif
+
+
+	// First Byte
+	ip++; forwardH = LZ4_HASH64K_VALUE(ip);
+
+	// Main Loop
+    for ( ; ; )
+	{
+		int findMatchAttempts = (1U << skipStrength) + 3;
+		const BYTE* forwardIp = ip;
+		const BYTE* ref;
+		BYTE* token;
+
+		// Find a match
+		do {
+			U32 h = forwardH;
+			int step = findMatchAttempts++ >> skipStrength;
+			ip = forwardIp;
+			forwardIp = ip + step;
+
+			if (forwardIp > mflimit) { goto _last_literals; }
+
+			forwardH = LZ4_HASH64K_VALUE(forwardIp);
+			ref = base + HashTable[h];
+			HashTable[h] = ip - base;
+
+		} while (A32(ref) != A32(ip));
+
+		// Catch up
+		while ((ip>anchor) && (ref>(BYTE*)source) && (ip[-1]==ref[-1])) { ip--; ref--; }
+
+		// Encode Literal length
+		length = ip - anchor;
+		token = op++;
+		if (length>=(int)RUN_MASK) { *token=(RUN_MASK<<ML_BITS); len = length-RUN_MASK; for(; len > 254 ; len-=255) *op++ = 255; *op++ = (BYTE)len; }
+		else *token = (length<<ML_BITS);
+
+		// Copy Literals
+		LZ4_BLINDCOPY(anchor, op, length);
+
+_next_match:
+		// Encode Offset
+		LZ4_WRITE_LITTLEENDIAN_16(op,ip-ref);
+
+		// Start Counting
+		ip+=MINMATCH; ref+=MINMATCH;   // MinMatch verified
+		anchor = ip;
+		while (ip<matchlimit-(STEPSIZE-1))
+		{
+			UARCH diff = AARCH(ref) ^ AARCH(ip);
+			if (!diff) { ip+=STEPSIZE; ref+=STEPSIZE; continue; }
+			ip += LZ4_NbCommonBytes(diff);
+			goto _endCount;
+		}
+		if (ARCH64) if ((ip<(matchlimit-3)) && (A32(ref) == A32(ip))) { ip+=4; ref+=4; }
+		if ((ip<(matchlimit-1)) && (A16(ref) == A16(ip))) { ip+=2; ref+=2; }
+		if ((ip<matchlimit) && (*ref == *ip)) ip++;
+_endCount:
+
+		// Encode MatchLength
+		len = (ip - anchor);
+		if (len>=(int)ML_MASK) { *token+=ML_MASK; len-=ML_MASK; for(; len > 509 ; len-=510) { *op++ = 255; *op++ = 255; } if (len > 254) { len-=255; *op++ = 255; } *op++ = (BYTE)len; }
+		else *token += len;
+
+		// Test end of chunk
+		if (ip > mflimit) { anchor = ip;  break; }
+
+		// Fill table
+		HashTable[LZ4_HASH64K_VALUE(ip-2)] = ip - 2 - base;
+
+		// Test next position
+		ref = base + HashTable[LZ4_HASH64K_VALUE(ip)];
+		HashTable[LZ4_HASH64K_VALUE(ip)] = ip - base;
+		if (A32(ref) == A32(ip)) { token = op++; *token=0; goto _next_match; }
+
+		// Prepare next loop
+		anchor = ip++;
+		forwardH = LZ4_HASH64K_VALUE(ip);
+	}
+
+_last_literals:
+	// Encode Last Literals
+	{
+		int lastRun = iend - anchor;
+		if (lastRun>=(int)RUN_MASK) { *op++=(RUN_MASK<<ML_BITS); lastRun-=RUN_MASK; for(; lastRun > 254 ; lastRun-=255) *op++ = 255; *op++ = (BYTE) lastRun; }
+		else *op++ = (lastRun<<ML_BITS);
+		memcpy(op, anchor, iend - anchor);
+		op += iend-anchor;
+	}
+
+	// End
+	return (int) (((char*)op)-dest);
+}
+
+
+
+int LZ4_compress(const char* source, 
+				 char* dest,
+				 int isize)
+{
+#if HEAPMODE
+	void* ctx = malloc(sizeof(struct refTables));
+	int result;
+	if (isize < LZ4_64KLIMIT)
+		result = LZ4_compress64kCtx(&ctx, source, dest, isize);
+	else result = LZ4_compressCtx(&ctx, source, dest, isize);
+	free(ctx);
+	return result;
+#else
+	if (isize < (int)LZ4_64KLIMIT) return LZ4_compress64kCtx(NULL, source, dest, isize);
+	return LZ4_compressCtx(NULL, source, dest, isize);
+#endif
+}
+
+
+
+
+//****************************
+// Decompression functions
+//****************************
+
+// Note : The decoding functions LZ4_uncompress() and LZ4_uncompress_unknownOutputSize()
+//		are safe against "buffer overflow" attack type.
+//		They will never write nor read outside of the provided input and output buffers.
+//		A corrupted input will produce an error result, a negative int, indicating the position of the error within input stream.
+
+int LZ4_uncompress(const char* source, 
+				 char* dest,
+				 int osize)
+{
+	// Local Variables
+	const BYTE* restrict ip = (const BYTE*) source;
+	const BYTE* restrict ref;
+
+	BYTE* restrict op = (BYTE*) dest;
+	BYTE* const oend = op + osize;
+	BYTE* cpy;
+
+	BYTE token;
+
+	int	len, length;
+	size_t dec[] ={0, 3, 2, 3, 0, 0, 0, 0};
+
+
+	// Main Loop
+	while (1)
+	{
+		// get runlength
+		token = *ip++;
+		if ((length=(token>>ML_BITS)) == RUN_MASK)  { for (;(len=*ip++)==255;length+=255){} length += len; }
+
+		// copy literals
+		cpy = op+length;
+		if (cpy>oend-COPYLENGTH)
+		{
+			if (cpy > oend) goto _output_error;
+			memcpy(op, ip, length);
+			ip += length;
+			break;    // Necessarily EOF
+		}
+		LZ4_WILDCOPY(ip, op, cpy); ip -= (op-cpy); op = cpy;
+
+		// get offset
+		LZ4_READ_LITTLEENDIAN_16(ref,cpy,ip); ip+=2;
+		if (ref < (BYTE* const)dest) goto _output_error;
+
+		// get matchlength
+		if ((length=(token&ML_MASK)) == ML_MASK) { for (;*ip==255;length+=255) {ip++;} length += *ip++; }
+
+		// copy repeated sequence
+		if (op-ref<STEPSIZE)
+		{
+#if ARCH64
+			size_t dec2table[]={0, 0, 0, -1, 0, 1, 2, 3};
+			size_t dec2 = dec2table[op-ref];
+#else
+			const int dec2 = 0;
+#endif
+			*op++ = *ref++;
+			*op++ = *ref++;
+			*op++ = *ref++;
+			*op++ = *ref++;
+			ref -= dec[op-ref];
+			A32(op)=A32(ref); op += STEPSIZE-4;
+			ref -= dec2;
+		} else { LZ4_COPYSTEP(ref,op); }
+		cpy = op + length - (STEPSIZE-4);
+		if (cpy>oend-COPYLENGTH)
+		{
+			if (cpy > oend) goto _output_error;
+			LZ4_SECURECOPY(ref, op, (oend-COPYLENGTH));
+			while(op<cpy) *op++=*ref++;
+			op=cpy;
+			if (op == oend) break;    // Check EOF (should never happen, since last 5 bytes are supposed to be literals)
+			continue;
+		}
+		LZ4_SECURECOPY(ref, op, cpy);
+		op=cpy;		// correction
+	}
+
+	// end of decoding
+	return (int) (((char*)ip)-source);
+
+	// write overflow error detected
+_output_error:
+	return (int) (-(((char*)ip)-source));
+}
+
+
+int LZ4_uncompress_unknownOutputSize(
+				const char* source, 
+				char* dest,
+				int isize,
+				int maxOutputSize)
+{
+	// Local Variables
+	const BYTE* restrict ip = (const BYTE*) source;
+	const BYTE* const iend = ip + isize;
+	const BYTE* restrict ref;
+
+	BYTE* restrict op = (BYTE*) dest;
+	BYTE* const oend = op + maxOutputSize;
+	BYTE* cpy;
+
+	BYTE token;
+
+	int	len, length;
+	size_t dec[] ={0, 3, 2, 3, 0, 0, 0, 0};
+
+
+	// Main Loop
+	while (ip<iend)
+	{
+		// get runlength
+		token = *ip++;
+		if ((length=(token>>ML_BITS)) == RUN_MASK)  { for (;(len=*ip++)==255;length+=255){} length += len; }
+
+		// copy literals
+		cpy = op+length;
+		if (cpy>oend-COPYLENGTH)
+		{
+			if (cpy > oend) goto _output_error;
+			memcpy(op, ip, length);
+			op += length;
+			break;    // Necessarily EOF
+		}
+		LZ4_WILDCOPY(ip, op, cpy); ip -= (op-cpy); op = cpy;
+		if (ip>=iend) break;    // check EOF
+
+		// get offset
+		LZ4_READ_LITTLEENDIAN_16(ref,cpy,ip); ip+=2;
+		if (ref < (BYTE* const)dest) goto _output_error;
+
+		// get matchlength
+		if ((length=(token&ML_MASK)) == ML_MASK) { for (;(len=*ip++)==255;length+=255){} length += len; }
+
+		// copy repeated sequence
+		if (op-ref<STEPSIZE)
+		{
+#if ARCH64
+			size_t dec2table[]={0, 0, 0, -1, 0, 1, 2, 3};
+			size_t dec2 = dec2table[op-ref];
+#else
+			const int dec2 = 0;
+#endif
+			*op++ = *ref++;
+			*op++ = *ref++;
+			*op++ = *ref++;
+			*op++ = *ref++;
+			ref -= dec[op-ref];
+			A32(op)=A32(ref); op += STEPSIZE-4;
+			ref -= dec2;
+		} else { LZ4_COPYSTEP(ref,op); }
+		cpy = op + length - (STEPSIZE-4);
+		if (cpy>oend-COPYLENGTH)
+		{
+			if (cpy > oend) goto _output_error;
+			LZ4_SECURECOPY(ref, op, (oend-COPYLENGTH));
+			while(op<cpy) *op++=*ref++;
+			op=cpy;
+			if (op == oend) break;    // Check EOF (should never happen, since last 5 bytes are supposed to be literals)
+			continue;
+		}
+		LZ4_SECURECOPY(ref, op, cpy);
+		op=cpy;		// correction
+	}
+
+	// end of decoding
+	return (int) (((char*)op)-dest);
+
+	// write overflow error detected
+_output_error:
+	return (int) (-(((char*)ip)-source));
+}
+
diff --git a/fs/btrfs/lz4.h b/fs/btrfs/lz4.h
new file mode 100644
index 0000000..bbd5e12
--- /dev/null
+++ b/fs/btrfs/lz4.h
@@ -0,0 +1,107 @@
+/*
+   LZ4 - Fast LZ compression algorithm
+   Header File
+   Copyright (C) 2011, Yann Collet.
+   BSD License
+
+   Redistribution and use in source and binary forms, with or without
+   modification, are permitted provided that the following conditions are
+   met:
+
+       * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+       * Redistributions in binary form must reproduce the above
+   copyright notice, this list of conditions and the following disclaimer
+   in the documentation and/or other materials provided with the
+   distribution.
+
+   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+/*
+ * With authors permission dual licensed as BSD/GPL for linux kernel
+ *
+ * Origin: http://lz4.googlecode.com/svn/trunk
+ * Revision: 54
+ */
+#pragma once
+
+#if defined (__cplusplus)
+extern "C" {
+#endif
+
+
+//****************************
+// Simple Functions
+//****************************
+
+int LZ4_compress   (const char* source, char* dest, int isize);
+int LZ4_uncompress (const char* source, char* dest, int osize);
+
+/*
+LZ4_compress() :
+	return : the number of bytes in compressed buffer dest
+	note : destination buffer must be already allocated.
+		To avoid any problem, size it to handle worst cases situations (input data not compressible)
+		Worst case size is : "inputsize + 0.4%", with "0.4%" being at least 8 bytes.
+
+LZ4_uncompress() :
+	osize  : is the output size, therefore the original size
+	return : the number of bytes read in the source buffer
+			 If the source stream is malformed, the function will stop decoding and return a negative result, indicating the byte position of the faulty instruction
+			 This version never writes beyond dest + osize, and is therefore protected against malicious data packets
+	note 2 : destination buffer must be already allocated
+*/
+
+
+//****************************
+// Advanced Functions
+//****************************
+
+int LZ4_uncompress_unknownOutputSize (const char* source, char* dest, int isize, int maxOutputSize);
+
+/*
+LZ4_uncompress_unknownOutputSize() :
+	isize  : is the input size, therefore the compressed size
+	maxOutputSize : is the size of the destination buffer (which must be already allocated)
+	return : the number of bytes decoded in the destination buffer (necessarily <= maxOutputSize)
+			 If the source stream is malformed, the function will stop decoding and return a negative result, indicating the byte position of the faulty instruction
+			 This version never writes beyond dest + maxOutputSize, and is therefore protected against malicious data packets
+	note   : This version is a bit slower than LZ4_uncompress
+*/
+
+
+int LZ4_compressCtx(void** ctx, const char* source,  char* dest, int isize);
+
+/*
+LZ4_compressCtx() :
+	This function explicitly handles the CTX memory structure.
+	It avoids allocating/deallocating memory between each call, improving performance when malloc is time-consuming.
+	Note : when memory is allocated into the stack (default mode), there is no "malloc" penalty.
+	Therefore, this function is mostly useful when memory is allocated into the heap (it requires increasing HASH_LOG value beyond STACK_LIMIT)
+
+	On first call : provide a *ctx=NULL; It will be automatically allocated.
+	On next calls : reuse the same ctx pointer.
+	Use different pointers for different threads when doing multi-threading.
+
+	note : performance difference is small, mostly noticeable in HeapMode when repetitively calling the compression function over many small segments.
+*/
+
+int LZ4_compress64kCtx(void** ctx,
+				 const char* source,
+				 char* dest,
+				 int isize);
+
+#if defined (__cplusplus)
+}
+#endif
-- 
1.7.8