From: Eric Sandeen <sandeen@redhat.com>
Date: Thu, 21 Aug 2008 15:34:10 -0500
Subject: [fs] ext4: new s390 bitops
Message-id: 48ADD142.8010005@redhat.com
O-Subject: [RHEL5.3 Patch 1/6] ext4: new s390 bitops
Bugzilla: 459436

[Bug 459436] ext4 assembly bitops failures on s390

Combination of patches to get ext4 going, with an eye towards
minimal invasiveness to the rest of the code.

Includes only code needed to implement ext2_find_next_bit, from the following
upstream patches:

--------------

From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Tue, 5 Feb 2008 15:50:43 +0000 (+0100)
Subject: [S390] Cleanup & optimize bitops.
X-Git-Tag: v2.6.25-rc1~786^2~7
X-Git-Url: http://git.engineering.redhat.com/?p=linux-2.6.git;a=commitdiff_plain;h=0abbf05cdd69d74f92628bf444cd210ba046f6eb

[S390] Cleanup & optimize bitops.

The bitops header is now a bit shorter and easier to understand since
it uses less inline assembly. It requires some tricks to persuade the
compiler to generate decent code. The ffz/ffs functions now use the
_zb_findmap/_sb_findmap table as well.
With this cleanup the new bitops for ext4 can be implemented with a
few lines, instead of another large inline assembly.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/include/asm-s390/bitops.h b/include/asm-s390/bitops.h
index 864d2bb..762b604 100644
--- a/include/asm-s390/bitops.h
+++ b/include/asm-s390/bitops.h
@@ -492,6 +492,95 @@ __constant_test_bit(unsigned long nr, const volatile unsigned long *addr) {
  __constant_test_bit((nr),(addr)) : \
  __test_bit((nr),(addr)) )
 
+
+/**
+ * __ffs_word_loop - find byte offset of first long != 0UL
+ * @addr: pointer to array of unsigned long
+ * @size: size of the array in bits
+ */
+static inline unsigned long __ffs_word_loop(const unsigned long *addr,
+					    unsigned long size)
+{
+	typedef struct { long _[__BITOPS_WORDS(size)]; } addrtype;
+	unsigned long bytes = 0;
+
+	asm volatile(
+#ifndef __s390x__
+		"	ahi	%1,-1\n"
+		"	sra	%1,5\n"
+		"	jz	1f\n"
+		"0:	c	%2,0(%0,%3)\n"
+		"	jne	1f\n"
+		"	la	%0,4(%0)\n"
+		"	brct	%1,0b\n"
+		"1:\n"
+#else
+		"	aghi	%1,-1\n"
+		"	srag	%1,%1,6\n"
+		"	jz	1f\n"
+		"0:	cg	%2,0(%0,%3)\n"
+		"	jne	1f\n"
+		"	la	%0,8(%0)\n"
+		"	brct	%1,0b\n"
+		"1:\n"
+#endif
+		: "+&a" (bytes), "+&a" (size)
+		: "d" (0UL), "a" (addr), "m" (*(addrtype *) addr)
+		: "cc" );
+	return bytes;
+}
+
+/**
+ * __ffs_word - add number of the first set bit
+ * @nr: base value the bit number is added to
+ * @word: the word that is searched for set bits
+ */
+static inline unsigned long __ffs_word(unsigned long nr, unsigned long word)
+{
+#ifdef __s390x__
+	if (likely((word & 0xffffffff) == 0)) {
+		word >>= 32;
+		nr += 32;
+	}
+#endif
+	if (likely((word & 0xffff) == 0)) {
+		word >>= 16;
+		nr += 16;
+	}
+	if (likely((word & 0xff) == 0)) {
+		word >>= 8;
+		nr += 8;
+	}
+	return nr + _sb_findmap[(unsigned char) word];
+}
+
+/**
+ * __load_ulong_le - load little endian unsigned long
+ * @p: pointer to array of unsigned long
+ * @offset: byte offset of source value in the array
+ */
+static inline unsigned long __load_ulong_le(const unsigned long *p,
+					    unsigned long offset)
+{
+	unsigned long word;
+
+	p = (unsigned long *)((unsigned long) p + offset);
+#ifndef __s390x__
+	asm volatile(
+		"	ic	%0,0(%1)\n"
+		"	icm	%0,2,1(%1)\n"
+		"	icm	%0,4,2(%1)\n"
+		"	icm	%0,8,3(%1)"
+		: "=&d" (word) : "a" (p), "m" (*p) : "cc");
+#else
+	asm volatile(
+		"	lrvg	%0,%1"
+		: "=d" (word) : "m" (*p) );
+#endif
+	return word;
+}
+
+
 /*
  * ffz = Find First Zero in word. Undefined if no zero exists,
  * so code should check against ~0UL first..
@@ -820,8 +909,6 @@ static inline int sched_find_first_bit(unsigned long *b)
 	test_and_clear_bit((nr)^(__BITOPS_WORDSIZE - 8), (unsigned long *)addr)
 #define ext2_test_bit(nr, addr)      \
 	test_bit((nr)^(__BITOPS_WORDSIZE - 8), (unsigned long *)addr)
-#define ext2_find_next_bit(addr, size, off) \
-	generic_find_next_le_bit((unsigned long *)(addr), (size), (off))
 
 #ifndef __s390x__
 
@@ -953,6 +1040,47 @@ ext2_find_next_zero_bit(void *vaddr, unsigned long size, unsigned long offset)
 	return offset + ext2_find_first_zero_bit(p, size);
 }
 
+static inline unsigned long ext2_find_first_bit(void *vaddr,
+						unsigned long size)
+{
+	unsigned long bytes, bits;
+
+	if (!size)
+		return 0;
+	bytes = __ffs_word_loop(vaddr, size);
+	bits = __ffs_word(bytes*8, __load_ulong_le(vaddr, bytes));
+	return (bits < size) ? bits : size;
+}
+
+static inline int ext2_find_next_bit(void *vaddr, unsigned long size,
+				     unsigned long offset)
+{
+	unsigned long *addr = vaddr, *p;
+	unsigned long bit, set;
+
+	if (offset >= size)
+		return size;
+	bit = offset & (__BITOPS_WORDSIZE - 1);
+	offset -= bit;
+	size -= offset;
+	p = addr + offset / __BITOPS_WORDSIZE;
+	if (bit) {
+		/*
+ 		 * s390 version of ffs returns __BITOPS_WORDSIZE
+ 		 * if no set bit is present in the word.
+ 		 */
+		set = __ffs_word(0, __load_ulong_le(p, 0) & (~0UL << bit));
+		if (set >= size)
+			return size + offset;
+		if (set < __BITOPS_WORDSIZE)
+			return set + offset;
+		offset += __BITOPS_WORDSIZE;
+		size -= __BITOPS_WORDSIZE;
+		p++;
+	}
+	return offset + ext2_find_first_bit(p, size);
+}
+
 #include <asm-generic/bitops/minix.h>
 
 #endif /* __KERNEL__ */