diff --git a/lib/lz4/lz4_decompress.c b/lib/lz4/lz4_decompress.c
index 141734d255e4..0c9d3ad17e0f 100644
--- a/lib/lz4/lz4_decompress.c
+++ b/lib/lz4/lz4_decompress.c
@@ -43,30 +43,36 @@
 /*-*****************************
  *	Decompression functions
  *******************************/
-/* LZ4_decompress_generic() :
- * This generic decompression function cover all use cases.
- * It shall be instantiated several times, using different sets of directives
- * Note that it is important this generic function is really inlined,
+
+#define DEBUGLOG(l, ...) {}	/* disabled */
+
+#ifndef assert
+#define assert(condition) ((void)0)
+#endif
+
+/*
+ * LZ4_decompress_generic() :
+ * This generic decompression function covers all use cases.
+ * It shall be instantiated several times, using different sets of directives.
+ * Note that it is important for performance that this function really get inlined,
  * in order to remove useless branches during compilation optimization.
  */
 static FORCE_INLINE int LZ4_decompress_generic(
-	 const char * const source,
-	 char * const dest,
-	 int inputSize,
+	 const char * const src,
+	 char * const dst,
+	 int srcSize,
 		/*
 		 * If endOnInput == endOnInputSize,
-		 * this value is the max size of Output Buffer.
+		 * this value is `dstCapacity`
 		 */
 	 int outputSize,
 	 /* endOnOutputSize, endOnInputSize */
-	 int endOnInput,
+	 endCondition_directive endOnInput,
 	 /* full, partial */
-	 int partialDecoding,
-	 /* only used if partialDecoding == partial */
-	 int targetOutputSize,
+	 earlyEnd_directive partialDecoding,
 	 /* noDict, withPrefix64k, usingExtDict */
-	 int dict,
-	 /* == dest when no prefix */
+	 dict_directive dict,
+	 /* always <= dst, == dst when no prefix */
 	 const BYTE * const lowPrefix,
 	 /* only if dict == usingExtDict */
 	 const BYTE * const dictStart,
@@ -74,35 +80,43 @@ static FORCE_INLINE int LZ4_decompress_generic(
 	 const size_t dictSize
 	 )
 {
-	/* Local Variables */
-	const BYTE *ip = (const BYTE *) source;
-	const BYTE * const iend = ip + inputSize;
+	const BYTE *ip = (const BYTE *) src;
+	const BYTE * const iend = ip + srcSize;
 
-	BYTE *op = (BYTE *) dest;
+	BYTE *op = (BYTE *) dst;
 	BYTE * const oend = op + outputSize;
 	BYTE *cpy;
-	BYTE *oexit = op + targetOutputSize;
-	const BYTE * const lowLimit = lowPrefix - dictSize;
 
 	const BYTE * const dictEnd = (const BYTE *)dictStart + dictSize;
-	static const unsigned int dec32table[] = { 0, 1, 2, 1, 4, 4, 4, 4 };
-	static const int dec64table[] = { 0, 0, 0, -1, 0, 1, 2, 3 };
+	static const unsigned int inc32table[8] = {0, 1, 2, 1, 0, 4, 4, 4};
+	static const int dec64table[8] = {0, 0, 0, -1, -4, 1, 2, 3};
 
 	const int safeDecode = (endOnInput == endOnInputSize);
 	const int checkOffset = ((safeDecode) && (dictSize < (int)(64 * KB)));
 
+	/* Set up the "end" pointers for the shortcut. */
+	const BYTE *const shortiend = iend -
+		(endOnInput ? 14 : 8) /*maxLL*/ - 2 /*offset*/;
+	const BYTE *const shortoend = oend -
+		(endOnInput ? 14 : 8) /*maxLL*/ - 18 /*maxML*/;
+
+	DEBUGLOG(5, "%s (srcSize:%i, dstSize:%i)", __func__,
+		 srcSize, outputSize);
+
 	/* Special cases */
-	/* targetOutputSize too high => decode everything */
-	if ((partialDecoding) && (oexit > oend - MFLIMIT))
-		oexit = oend - MFLIMIT;
+	assert(lowPrefix <= op);
+	assert(src != NULL);
 
 	/* Empty output buffer */
 	if ((endOnInput) && (unlikely(outputSize == 0)))
-		return ((inputSize == 1) && (*ip == 0)) ? 0 : -1;
+		return ((srcSize == 1) && (*ip == 0)) ? 0 : -1;
 
 	if ((!endOnInput) && (unlikely(outputSize == 0)))
 		return (*ip == 0 ? 1 : -1);
 
+	if ((endOnInput) && unlikely(srcSize == 0))
+		return -1;
+
 	/* Main Loop : decode sequences */
 	while (1) {
 		size_t length;
@@ -111,12 +125,74 @@ static FORCE_INLINE int LZ4_decompress_generic(
 
 		/* get literal length */
 		unsigned int const token = *ip++;
-
 		length = token>>ML_BITS;
 
+		/* ip < iend before the increment */
+		assert(!endOnInput || ip <= iend);
+
+		/*
+		 * A two-stage shortcut for the most common case:
+		 * 1) If the literal length is 0..14, and there is enough
+		 * space, enter the shortcut and copy 16 bytes on behalf
+		 * of the literals (in the fast mode, only 8 bytes can be
+		 * safely copied this way).
+		 * 2) Further if the match length is 4..18, copy 18 bytes
+		 * in a similar manner; but we ensure that there's enough
+		 * space in the output for those 18 bytes earlier, upon
+		 * entering the shortcut (in other words, there is a
+		 * combined check for both stages).
+		 */
+		if ((endOnInput ? length != RUN_MASK : length <= 8)
+		   /*
+		    * strictly "less than" on input, to re-enter
+		    * the loop with at least one byte
+		    */
+		   && likely((endOnInput ? ip < shortiend : 1) &
+			     (op <= shortoend))) {
+			/* Copy the literals */
+			memcpy(op, ip, endOnInput ? 16 : 8);
+			op += length; ip += length;
+
+			/*
+			 * The second stage:
+			 * prepare for match copying, decode full info.
+			 * If it doesn't work out, the info won't be wasted.
+			 */
+			length = token & ML_MASK; /* match length */
+			offset = LZ4_readLE16(ip);
+			ip += 2;
+			match = op - offset;
+			assert(match <= op); /* check overflow */
+
+			/* Do not deal with overlapping matches. */
+			if ((length != ML_MASK) &&
+			    (offset >= 8) &&
+			    (dict == withPrefix64k || match >= lowPrefix)) {
+				/* Copy the match. */
+				memcpy(op + 0, match + 0, 8);
+				memcpy(op + 8, match + 8, 8);
+				memcpy(op + 16, match + 16, 2);
+				op += length + MINMATCH;
+				/* Both stages worked, load the next token. */
+				continue;
+			}
+
+			/*
+			 * The second stage didn't work out, but the info
+			 * is ready. Propel it right to the point of match
+			 * copying.
+			 */
+			goto _copy_match;
+		}
+
+		/* decode literal length */
 		if (length == RUN_MASK) {
 			unsigned int s;
 
+			if (unlikely(endOnInput ? ip >= iend - RUN_MASK : 0)) {
+				/* overflow detection */
+				goto _output_error;
+			}
 			do {
 				s = *ip++;
 				length += s;
@@ -125,14 +201,14 @@ static FORCE_INLINE int LZ4_decompress_generic(
 				: 1) & (s == 255));
 
 			if ((safeDecode)
-				&& unlikely(
-					(size_t)(op + length) < (size_t)(op))) {
+			    && unlikely((uptrval)(op) +
+					length < (uptrval)(op))) {
 				/* overflow detection */
 				goto _output_error;
 			}
 			if ((safeDecode)
-				&& unlikely(
-					(size_t)(ip + length) < (size_t)(ip))) {
+			    && unlikely((uptrval)(ip) +
+					length < (uptrval)(ip))) {
 				/* overflow detection */
 				goto _output_error;
 			}
@@ -140,16 +216,19 @@ static FORCE_INLINE int LZ4_decompress_generic(
 
 		/* copy literals */
 		cpy = op + length;
-		if (((endOnInput) && ((cpy > (partialDecoding ? oexit : oend - MFLIMIT))
+		LZ4_STATIC_ASSERT(MFLIMIT >= WILDCOPYLENGTH);
+
+		if (((endOnInput) && ((cpy > oend - MFLIMIT)
 			|| (ip + length > iend - (2 + 1 + LASTLITERALS))))
 			|| ((!endOnInput) && (cpy > oend - WILDCOPYLENGTH))) {
 			if (partialDecoding) {
 				if (cpy > oend) {
 					/*
-					 * Error :
-					 * write attempt beyond end of output buffer
+					 * Partial decoding :
+					 * stop in the middle of literal segment
 					 */
-					goto _output_error;
+					cpy = oend;
+					length = oend - op;
 				}
 				if ((endOnInput)
 					&& (ip + length > iend)) {
@@ -184,29 +263,43 @@ static FORCE_INLINE int LZ4_decompress_generic(
 			memcpy(op, ip, length);
 			ip += length;
 			op += length;
-			/* Necessarily EOF, due to parsing restrictions */
-			break;
-		}
 
-		LZ4_wildCopy(op, ip, cpy);
-		ip += length;
-		op = cpy;
+			/* Necessarily EOF, due to parsing restrictions */
+			if (!partialDecoding || (cpy == oend))
+				break;
+		} else {
+			/* may overwrite up to WILDCOPYLENGTH beyond cpy */
+			LZ4_wildCopy(op, ip, cpy);
+			ip += length;
+			op = cpy;
+		}
 
 		/* get offset */
 		offset = LZ4_readLE16(ip);
 		ip += 2;
 		match = op - offset;
 
-		if ((checkOffset) && (unlikely(match < lowLimit))) {
+		/* get matchlength */
+		length = token & ML_MASK;
+
+_copy_match:
+		if ((checkOffset) && (unlikely(match + dictSize < lowPrefix))) {
 			/* Error : offset outside buffers */
 			goto _output_error;
 		}
 
 		/* costs ~1%; silence an msan warning when offset == 0 */
-		LZ4_write32(op, (U32)offset);
+		/*
+		 * note : when partialDecoding, there is no guarantee that
+		 * at least 4 bytes remain available in output buffer
+		 */
+		if (!partialDecoding) {
+			assert(oend > op);
+			assert(oend - op >= 4);
+
+			LZ4_write32(op, (U32)offset);
+		}
 
-		/* get matchlength */
-		length = token & ML_MASK;
 		if (length == ML_MASK) {
 			unsigned int s;
 
@@ -221,7 +314,7 @@ static FORCE_INLINE int LZ4_decompress_generic(
 
 			if ((safeDecode)
 				&& unlikely(
-					(size_t)(op + length) < (size_t)op)) {
+					(uptrval)(op) + length < (uptrval)op)) {
 				/* overflow detection */
 				goto _output_error;
 			}
@@ -229,24 +322,26 @@ static FORCE_INLINE int LZ4_decompress_generic(
 
 		length += MINMATCH;
 
-		/* check external dictionary */
+		/* match starting within external dictionary */
 		if ((dict == usingExtDict) && (match < lowPrefix)) {
 			if (unlikely(op + length > oend - LASTLITERALS)) {
 				/* doesn't respect parsing restriction */
-				goto _output_error;
+				if (!partialDecoding)
+					goto _output_error;
+				length = min(length, (size_t)(oend - op));
 			}
 
 			if (length <= (size_t)(lowPrefix - match)) {
 				/*
-				 * match can be copied as a single segment
-				 * from external dictionary
+				 * match fits entirely within external
+				 * dictionary : just copy
 				 */
 				memmove(op, dictEnd - (lowPrefix - match),
 					length);
 				op += length;
 			} else {
 				/*
-				 * match encompass external
+				 * match stretches into both external
 				 * dictionary and current block
 				 */
 				size_t const copySize = (size_t)(lowPrefix - match);
@@ -254,7 +349,6 @@ static FORCE_INLINE int LZ4_decompress_generic(
 
 				memcpy(op, dictEnd - copySize, copySize);
 				op += copySize;
-
 				if (restSize > (size_t)(op - lowPrefix)) {
 					/* overlap copy */
 					BYTE * const endOfMatch = op + restSize;
@@ -267,23 +361,44 @@ static FORCE_INLINE int LZ4_decompress_generic(
 					op += restSize;
 				}
 			}
-
 			continue;
 		}
 
 		/* copy match within block */
 		cpy = op + length;
 
-		if (unlikely(offset < 8)) {
-			const int dec64 = dec64table[offset];
+		/*
+		 * partialDecoding :
+		 * may not respect endBlock parsing restrictions
+		 */
+		assert(op <= oend);
+		if (partialDecoding &&
+		    (cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
+			size_t const mlen = min(length, (size_t)(oend - op));
+			const BYTE * const matchEnd = match + mlen;
+			BYTE * const copyEnd = op + mlen;
 
+			if (matchEnd > op) {
+				/* overlap copy */
+				while (op < copyEnd)
+					*op++ = *match++;
+			} else {
+				memcpy(op, match, mlen);
+			}
+			op = copyEnd;
+			if (op == oend)
+				break;
+			continue;
+		}
+
+		if (unlikely(offset < 8)) {
 			op[0] = match[0];
 			op[1] = match[1];
 			op[2] = match[2];
 			op[3] = match[3];
-			match += dec32table[offset];
+			match += inc32table[offset];
 			memcpy(op + 4, match, 4);
-			match -= dec64;
+			match -= dec64table[offset];
 		} else {
 			LZ4_copy8(op, match);
 			match += 8;
@@ -291,7 +406,7 @@ static FORCE_INLINE int LZ4_decompress_generic(
 
 		op += 8;
 
-		if (unlikely(cpy > oend - 12)) {
+		if (unlikely(cpy > oend - MATCH_SAFEGUARD_DISTANCE)) {
 			BYTE * const oCopyLimit = oend - (WILDCOPYLENGTH - 1);
 
 			if (cpy > oend - LASTLITERALS) {
@@ -307,60 +422,139 @@ static FORCE_INLINE int LZ4_decompress_generic(
 				match += oCopyLimit - op;
 				op = oCopyLimit;
 			}
-
 			while (op < cpy)
 				*op++ = *match++;
 		} else {
 			LZ4_copy8(op, match);
-
 			if (length > 16)
 				LZ4_wildCopy(op + 8, match + 8, cpy);
 		}
-
-		op = cpy; /* correction */
+		op = cpy; /* wildcopy correction */
 	}
 
 	/* end of decoding */
 	if (endOnInput) {
 		/* Nb of output bytes decoded */
-		return (int) (((char *)op) - dest);
+		return (int) (((char *)op) - dst);
 	} else {
 		/* Nb of input bytes read */
-		return (int) (((const char *)ip) - source);
+		return (int) (((const char *)ip) - src);
 	}
 
 	/* Overflow error detected */
 _output_error:
-	return -1;
+	return (int) (-(((const char *)ip) - src)) - 1;
 }
 
 int LZ4_decompress_safe(const char *source, char *dest,
 	int compressedSize, int maxDecompressedSize)
 {
-	return LZ4_decompress_generic(source, dest, compressedSize,
-		maxDecompressedSize, endOnInputSize, full, 0,
-		noDict, (BYTE *)dest, NULL, 0);
+	return LZ4_decompress_generic(source, dest,
+				      compressedSize, maxDecompressedSize,
+				      endOnInputSize, decode_full_block,
+				      noDict, (BYTE *)dest, NULL, 0);
 }
 
-int LZ4_decompress_safe_partial(const char *source, char *dest,
-	int compressedSize, int targetOutputSize, int maxDecompressedSize)
+int LZ4_decompress_safe_partial(const char *src, char *dst,
+	int compressedSize, int targetOutputSize, int dstCapacity)
 {
-	return LZ4_decompress_generic(source, dest, compressedSize,
-		maxDecompressedSize, endOnInputSize, partial,
-		targetOutputSize, noDict, (BYTE *)dest, NULL, 0);
+	dstCapacity = min(targetOutputSize, dstCapacity);
+	return LZ4_decompress_generic(src, dst, compressedSize, dstCapacity,
+				      endOnInputSize, partial_decode,
+				      noDict, (BYTE *)dst, NULL, 0);
 }
 
 int LZ4_decompress_fast(const char *source, char *dest, int originalSize)
 {
 	return LZ4_decompress_generic(source, dest, 0, originalSize,
-		endOnOutputSize, full, 0, withPrefix64k,
-		(BYTE *)(dest - 64 * KB), NULL, 64 * KB);
+				      endOnOutputSize, decode_full_block,
+				      withPrefix64k,
+				      (BYTE *)dest - 64 * KB, NULL, 0);
 }
 
+/* ===== Instantiate a few more decoding cases, used more than once. ===== */
+
+int LZ4_decompress_safe_withPrefix64k(const char *source, char *dest,
+				      int compressedSize, int maxOutputSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      compressedSize, maxOutputSize,
+				      endOnInputSize, decode_full_block,
+				      withPrefix64k,
+				      (BYTE *)dest - 64 * KB, NULL, 0);
+}
+
+static int LZ4_decompress_safe_withSmallPrefix(const char *source, char *dest,
+					       int compressedSize,
+					       int maxOutputSize,
+					       size_t prefixSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      compressedSize, maxOutputSize,
+				      endOnInputSize, decode_full_block,
+				      noDict,
+				      (BYTE *)dest - prefixSize, NULL, 0);
+}
+
+int LZ4_decompress_safe_forceExtDict(const char *source, char *dest,
+				     int compressedSize, int maxOutputSize,
+				     const void *dictStart, size_t dictSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      compressedSize, maxOutputSize,
+				      endOnInputSize, decode_full_block,
+				      usingExtDict, (BYTE *)dest,
+				      (const BYTE *)dictStart, dictSize);
+}
+
+static int LZ4_decompress_fast_extDict(const char *source, char *dest,
+				       int originalSize,
+				       const void *dictStart, size_t dictSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      0, originalSize,
+				      endOnOutputSize, decode_full_block,
+				      usingExtDict, (BYTE *)dest,
+				      (const BYTE *)dictStart, dictSize);
+}
+
+/*
+ * The "double dictionary" mode, for use with e.g. ring buffers: the first part
+ * of the dictionary is passed as prefix, and the second via dictStart + dictSize.
+ * These routines are used only once, in LZ4_decompress_*_continue().
+ */
+static FORCE_INLINE
+int LZ4_decompress_safe_doubleDict(const char *source, char *dest,
+				   int compressedSize, int maxOutputSize,
+				   size_t prefixSize,
+				   const void *dictStart, size_t dictSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      compressedSize, maxOutputSize,
+				      endOnInputSize, decode_full_block,
+				      usingExtDict, (BYTE *)dest - prefixSize,
+				      (const BYTE *)dictStart, dictSize);
+}
+
+static FORCE_INLINE
+int LZ4_decompress_fast_doubleDict(const char *source, char *dest,
+				   int originalSize, size_t prefixSize,
+				   const void *dictStart, size_t dictSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      0, originalSize,
+				      endOnOutputSize, decode_full_block,
+				      usingExtDict, (BYTE *)dest - prefixSize,
+				      (const BYTE *)dictStart, dictSize);
+}
+
+/* ===== streaming decompression functions ===== */
+
 int LZ4_setStreamDecode(LZ4_streamDecode_t *LZ4_streamDecode,
 	const char *dictionary, int dictSize)
 {
-	LZ4_streamDecode_t_internal *lz4sd = (LZ4_streamDecode_t_internal *) LZ4_streamDecode;
+	LZ4_streamDecode_t_internal *lz4sd =
+		&LZ4_streamDecode->internal_donotuse;
 
 	lz4sd->prefixSize = (size_t) dictSize;
 	lz4sd->prefixEnd = (const BYTE *) dictionary + dictSize;
@@ -382,35 +576,51 @@ int LZ4_setStreamDecode(LZ4_streamDecode_t *LZ4_streamDecode,
 int LZ4_decompress_safe_continue(LZ4_streamDecode_t *LZ4_streamDecode,
 	const char *source, char *dest, int compressedSize, int maxOutputSize)
 {
-	LZ4_streamDecode_t_internal *lz4sd = &LZ4_streamDecode->internal_donotuse;
+	LZ4_streamDecode_t_internal *lz4sd =
+		&LZ4_streamDecode->internal_donotuse;
 	int result;
 
-	if (lz4sd->prefixEnd == (BYTE *)dest) {
-		result = LZ4_decompress_generic(source, dest,
-			compressedSize,
-			maxOutputSize,
-			endOnInputSize, full, 0,
-			usingExtDict, lz4sd->prefixEnd - lz4sd->prefixSize,
-			lz4sd->externalDict,
-			lz4sd->extDictSize);
-
+	if (lz4sd->prefixSize == 0) {
+		/* The first call, no dictionary yet. */
+		assert(lz4sd->extDictSize == 0);
+		result = LZ4_decompress_safe(source, dest,
+			compressedSize, maxOutputSize);
+		if (result <= 0)
+			return result;
+		lz4sd->prefixSize = result;
+		lz4sd->prefixEnd = (BYTE *)dest + result;
+	} else if (lz4sd->prefixEnd == (BYTE *)dest) {
+		/* They're rolling the current segment. */
+		if (lz4sd->prefixSize >= 64 * KB - 1)
+			result = LZ4_decompress_safe_withPrefix64k(source, dest,
+				compressedSize, maxOutputSize);
+		else if (lz4sd->extDictSize == 0)
+			result = LZ4_decompress_safe_withSmallPrefix(source,
+				dest, compressedSize, maxOutputSize,
+				lz4sd->prefixSize);
+		else
+			result = LZ4_decompress_safe_doubleDict(source, dest,
+				compressedSize, maxOutputSize,
+				lz4sd->prefixSize,
+				lz4sd->externalDict, lz4sd->extDictSize);
 		if (result <= 0)
 			return result;
-
 		lz4sd->prefixSize += result;
-		lz4sd->prefixEnd	+= result;
+		lz4sd->prefixEnd  += result;
 	} else {
+		/*
+		 * The buffer wraps around, or they're
+		 * switching to another buffer.
+		 */
 		lz4sd->extDictSize = lz4sd->prefixSize;
 		lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
-		result = LZ4_decompress_generic(source, dest,
+		result = LZ4_decompress_safe_forceExtDict(source, dest,
 			compressedSize, maxOutputSize,
-			endOnInputSize, full, 0,
-			usingExtDict, (BYTE *)dest,
 			lz4sd->externalDict, lz4sd->extDictSize);
 		if (result <= 0)
 			return result;
 		lz4sd->prefixSize = result;
-		lz4sd->prefixEnd	= (BYTE *)dest + result;
+		lz4sd->prefixEnd  = (BYTE *)dest + result;
 	}
 
 	return result;
@@ -422,75 +632,66 @@ int LZ4_decompress_fast_continue(LZ4_streamDecode_t *LZ4_streamDecode,
 	LZ4_streamDecode_t_internal *lz4sd = &LZ4_streamDecode->internal_donotuse;
 	int result;
 
-	if (lz4sd->prefixEnd == (BYTE *)dest) {
-		result = LZ4_decompress_generic(source, dest, 0, originalSize,
-			endOnOutputSize, full, 0,
-			usingExtDict,
-			lz4sd->prefixEnd - lz4sd->prefixSize,
-			lz4sd->externalDict, lz4sd->extDictSize);
-
-		if (result <= 0)
-			return result;
-
-		lz4sd->prefixSize += originalSize;
-		lz4sd->prefixEnd	+= originalSize;
-	} else {
-		lz4sd->extDictSize = lz4sd->prefixSize;
-		lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
-		result = LZ4_decompress_generic(source, dest, 0, originalSize,
-			endOnOutputSize, full, 0,
-			usingExtDict, (BYTE *)dest,
-			lz4sd->externalDict, lz4sd->extDictSize);
+	if (lz4sd->prefixSize == 0) {
+		assert(lz4sd->extDictSize == 0);
+		result = LZ4_decompress_fast(source, dest, originalSize);
 		if (result <= 0)
 			return result;
 		lz4sd->prefixSize = originalSize;
-		lz4sd->prefixEnd	= (BYTE *)dest + originalSize;
+		lz4sd->prefixEnd = (BYTE *)dest + originalSize;
+	} else if (lz4sd->prefixEnd == (BYTE *)dest) {
+		if (lz4sd->prefixSize >= 64 * KB - 1 ||
+		    lz4sd->extDictSize == 0)
+			result = LZ4_decompress_fast(source, dest,
+						     originalSize);
+		else
+			result = LZ4_decompress_fast_doubleDict(source, dest,
+				originalSize, lz4sd->prefixSize,
+				lz4sd->externalDict, lz4sd->extDictSize);
+		if (result <= 0)
+			return result;
+		lz4sd->prefixSize += originalSize;
+		lz4sd->prefixEnd  += originalSize;
+	} else {
+		lz4sd->extDictSize = lz4sd->prefixSize;
+		lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
+		result = LZ4_decompress_fast_extDict(source, dest,
+			originalSize, lz4sd->externalDict, lz4sd->extDictSize);
+		if (result <= 0)
+			return result;
+		lz4sd->prefixSize = originalSize;
+		lz4sd->prefixEnd = (BYTE *)dest + originalSize;
 	}
-
 	return result;
 }
 
-/*
- * Advanced decoding functions :
- * *_usingDict() :
- * These decoding functions work the same as "_continue" ones,
- * the dictionary must be explicitly provided within parameters
- */
-static FORCE_INLINE int LZ4_decompress_usingDict_generic(const char *source,
-	char *dest, int compressedSize, int maxOutputSize, int safe,
-	const char *dictStart, int dictSize)
+int LZ4_decompress_safe_usingDict(const char *source, char *dest,
+				  int compressedSize, int maxOutputSize,
+				  const char *dictStart, int dictSize)
 {
 	if (dictSize == 0)
-		return LZ4_decompress_generic(source, dest,
-			compressedSize, maxOutputSize, safe, full, 0,
-			noDict, (BYTE *)dest, NULL, 0);
-	if (dictStart + dictSize == dest) {
-		if (dictSize >= (int)(64 * KB - 1))
-			return LZ4_decompress_generic(source, dest,
-				compressedSize, maxOutputSize, safe, full, 0,
-				withPrefix64k, (BYTE *)dest - 64 * KB, NULL, 0);
-		return LZ4_decompress_generic(source, dest, compressedSize,
-			maxOutputSize, safe, full, 0, noDict,
-			(BYTE *)dest - dictSize, NULL, 0);
+		return LZ4_decompress_safe(source, dest,
+					   compressedSize, maxOutputSize);
+	if (dictStart+dictSize == dest) {
+		if (dictSize >= 64 * KB - 1)
+			return LZ4_decompress_safe_withPrefix64k(source, dest,
+				compressedSize, maxOutputSize);
+		return LZ4_decompress_safe_withSmallPrefix(source, dest,
+			compressedSize, maxOutputSize, dictSize);
 	}
-	return LZ4_decompress_generic(source, dest, compressedSize,
-		maxOutputSize, safe, full, 0, usingExtDict,
-		(BYTE *)dest, (const BYTE *)dictStart, dictSize);
-}
-
-int LZ4_decompress_safe_usingDict(const char *source, char *dest,
-	int compressedSize, int maxOutputSize,
-	const char *dictStart, int dictSize)
-{
-	return LZ4_decompress_usingDict_generic(source, dest,
-		compressedSize, maxOutputSize, 1, dictStart, dictSize);
+	return LZ4_decompress_safe_forceExtDict(source, dest,
+		compressedSize, maxOutputSize, dictStart, dictSize);
 }
 
 int LZ4_decompress_fast_usingDict(const char *source, char *dest,
-	int originalSize, const char *dictStart, int dictSize)
+				  int originalSize,
+				  const char *dictStart, int dictSize)
 {
-	return LZ4_decompress_usingDict_generic(source, dest, 0,
-		originalSize, 0, dictStart, dictSize);
+	if (dictSize == 0 || dictStart + dictSize == dest)
+		return LZ4_decompress_fast(source, dest, originalSize);
+
+	return LZ4_decompress_fast_extDict(source, dest, originalSize,
+		dictStart, dictSize);
 }
 
 #ifndef STATIC
diff --git a/lib/lz4/lz4defs.h b/lib/lz4/lz4defs.h
index 00a0b58a0871..1a7fa9d9170f 100644
--- a/lib/lz4/lz4defs.h
+++ b/lib/lz4/lz4defs.h
@@ -75,6 +75,11 @@ typedef uintptr_t uptrval;
 #define WILDCOPYLENGTH 8
 #define LASTLITERALS 5
 #define MFLIMIT (WILDCOPYLENGTH + MINMATCH)
+/*
+ * ensure it's possible to write 2 x wildcopyLength
+ * without overflowing output buffer
+ */
+#define MATCH_SAFEGUARD_DISTANCE  ((2 * WILDCOPYLENGTH) - MINMATCH)
 
 /* Increase this value ==> compression run slower on incompressible data */
 #define LZ4_SKIPTRIGGER 6
@@ -222,6 +227,8 @@ typedef enum { noDict = 0, withPrefix64k, usingExtDict } dict_directive;
 typedef enum { noDictIssue = 0, dictSmall } dictIssue_directive;
 
 typedef enum { endOnOutputSize = 0, endOnInputSize = 1 } endCondition_directive;
-typedef enum { full = 0, partial = 1 } earlyEnd_directive;
+typedef enum { decode_full_block = 0, partial_decode = 1 } earlyEnd_directive;
+
+#define LZ4_STATIC_ASSERT(c)	BUILD_BUG_ON(!(c))
 
 #endif