From 86f6309949a8769a38b9f8ab5e7929645c5f8760 Mon Sep 17 00:00:00 2001
From: Andrea Mazzoleni <amadvance@gmail.com>
Date: Thu, 26 Dec 2013 08:25:32 +0100
Subject: [PATCH] Supports the special case of a single data disk for all
 parity levels.

---
 raid.c     | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 raid.h     |  7 ------
 selftest.c |  1 +
 state.c    |  5 -----
 4 files changed, 65 insertions(+), 12 deletions(-)

diff --git a/raid.c b/raid.c
index df63498c..6432a11f 100644
--- a/raid.c
+++ b/raid.c
@@ -886,6 +886,14 @@ void raid_par3_ssse3(unsigned char** vbuf, unsigned data, unsigned size)
 	q = vbuf[data+1];
 	r = vbuf[data+2];
 
+	/* special case with only one data disk */
+	if (l == 0) {
+		for(i=0;i<3;++i)
+			memcpy(vbuf[1+i], vbuf[0], size);
+		return;
+	}
+
+	/* generic case with at least two data disks */
 	asm volatile("movdqa %0,%%xmm3" : : "m" (gfconst16.poly[0]));
 	asm volatile("movdqa %0,%%xmm7" : : "m" (gfconst16.low4[0]));
 
@@ -974,6 +982,14 @@ void raid_par3_ssse3ext(unsigned char** vbuf, unsigned data, unsigned size)
 	q = vbuf[data+1];
 	r = vbuf[data+2];
 
+	/* special case with only one data disk */
+	if (l == 0) {
+		for(i=0;i<3;++i)
+			memcpy(vbuf[1+i], vbuf[0], size);
+		return;
+	}
+
+	/* generic case with at least two data disks */
 	asm volatile("movdqa %0,%%xmm3" : : "m" (gfconst16.poly[0]));
 	asm volatile("movdqa %0,%%xmm11" : : "m" (gfconst16.low4[0]));
 
@@ -1155,6 +1171,14 @@ void raid_par4_ssse3(unsigned char** vbuf, unsigned data, unsigned size)
 	r = vbuf[data+2];
 	s = vbuf[data+3];
 
+	/* special case with only one data disk */
+	if (l == 0) {
+		for(i=0;i<4;++i)
+			memcpy(vbuf[1+i], vbuf[0], size);
+		return;
+	}
+
+	/* generic case with at least two data disks */
 	for(i=0;i<size;i+=16) {
 		/* last disk without the by two multiplication */
 		asm volatile("movdqa %0,%%xmm7" : : "m" (gfconst16.low4[0]));
@@ -1262,6 +1286,14 @@ void raid_par4_ssse3ext(unsigned char** vbuf, unsigned data, unsigned size)
 	r = vbuf[data+2];
 	s = vbuf[data+3];
 
+	/* special case with only one data disk */
+	if (l == 0) {
+		for(i=0;i<4;++i)
+			memcpy(vbuf[1+i], vbuf[0], size);
+		return;
+	}
+
+	/* generic case with at least two data disks */
 	for(i=0;i<size;i+=32) {
 		/* last disk without the by two multiplication */
 		asm volatile("movdqa %0,%%xmm15" : : "m" (gfconst16.low4[0]));
@@ -1486,6 +1518,14 @@ void raid_par5_ssse3(unsigned char** vbuf, unsigned data, unsigned size)
 	s = vbuf[data+3];
 	t = vbuf[data+4];
 
+	/* special case with only one data disk */
+	if (l == 0) {
+		for(i=0;i<5;++i)
+			memcpy(vbuf[1+i], vbuf[0], size);
+		return;
+	}
+
+	/* generic case with at least two data disks */
 	for(i=0;i<size;i+=16) {
 		/* last disk without the by two multiplication */
 		asm volatile("movdqa %0,%%xmm4" : : "m" (vbuf[l][i]));
@@ -1612,6 +1652,14 @@ void raid_par5_ssse3ext(unsigned char** vbuf, unsigned data, unsigned size)
 	s = vbuf[data+3];
 	t = vbuf[data+4];
 
+	/* special case with only one data disk */
+	if (l == 0) {
+		for(i=0;i<5;++i)
+			memcpy(vbuf[1+i], vbuf[0], size);
+		return;
+	}
+
+	/* generic case with at least two data disks */
 	asm volatile("movdqa %0,%%xmm14" : : "m" (gfconst16.poly[0]));
 	asm volatile("movdqa %0,%%xmm15" : : "m" (gfconst16.low4[0]));
 
@@ -1801,6 +1849,14 @@ void raid_par6_ssse3(unsigned char** vbuf, unsigned data, unsigned size)
 	t = vbuf[data+4];
 	u = vbuf[data+5];
 
+	/* special case with only one data disk */
+	if (l == 0) {
+		for(i=0;i<6;++i)
+			memcpy(vbuf[1+i], vbuf[0], size);
+		return;
+	}
+
+	/* generic case with at least two data disks */
 	for(i=0;i<size;i+=16) {
 		/* last disk without the by two multiplication */
 		asm volatile("movdqa %0,%%xmm4" : : "m" (vbuf[l][i]));
@@ -1948,6 +2004,14 @@ void raid_par6_ssse3ext(unsigned char** vbuf, unsigned data, unsigned size)
 	t = vbuf[data+4];
 	u = vbuf[data+5];
 
+	/* special case with only one data disk */
+	if (l == 0) {
+		for(i=0;i<6;++i)
+			memcpy(vbuf[1+i], vbuf[0], size);
+		return;
+	}
+
+	/* generic case with at least two data disks */
 	asm volatile("movdqa %0,%%xmm14" : : "m" (gfconst16.poly[0]));
 	asm volatile("movdqa %0,%%xmm15" : : "m" (gfconst16.low4[0]));
 
diff --git a/raid.h b/raid.h
index 1e21cb63..d293da58 100644
--- a/raid.h
+++ b/raid.h
@@ -56,13 +56,6 @@
  */
 #define RAID_DATA_MAX 251
 
-/**
- * Minimum number of data disks.
- * Some optimizations require at least two disks.
- * It's anyway allowed to have a single data disk with a sigle parity.
- */
-#define RAID_DATA_MIN 2
-
 /**
  * Initializes the RAID system.
  */
diff --git a/selftest.c b/selftest.c
index 0a5a9b2e..9505f1b3 100644
--- a/selftest.c
+++ b/selftest.c
@@ -429,5 +429,6 @@ void selftest()
 	recovtest(RAID_MODE_VANDERMONDE, 12, 256);
 	gentest(RAID_MODE_CAUCHY, 32, 256);
 	recovtest(RAID_MODE_CAUCHY, 12, 256);
+	gentest(RAID_MODE_CAUCHY, 1, 256);
 }
 
diff --git a/state.c b/state.c
index 8c030f80..bbdfb279 100644
--- a/state.c
+++ b/state.c
@@ -895,11 +895,6 @@ static void state_map(struct snapraid_state* state)
 		fprintf(stderr, "Too many data disks. No more than %u.\n", RAID_DATA_MAX);
 		exit(EXIT_FAILURE);
 	}
-	/* some raid functions assume at least two data disk */
-	if (state->level > 1 && diskcount < RAID_DATA_MIN) {
-		fprintf(stderr, "Too few data disks. You must define at least %u.\n", RAID_DATA_MIN);
-		exit(EXIT_FAILURE);
-	}
 
 	/* recommend number of parities */
 	if (diskcount >= 36 && state->level < 6) {