[PATCH 1/3] devmem: make size_inside_page() logic straight

[Wu Fengguang]

Also convert more size_inside_page() users.

Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Avi Kivity <avi@xxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
 drivers/char/mem.c |   34 ++++++++++++----------------------
 1 file changed, 12 insertions(+), 22 deletions(-)

--- linux-mm.orig/drivers/char/mem.c	2009-09-12 23:01:24.000000000 +0800
+++ linux-mm/drivers/char/mem.c	2009-09-12 23:01:25.000000000 +0800
@@ -40,12 +40,9 @@ static inline unsigned long size_inside_
 {
 	unsigned long sz;
 
-	if (-start & (PAGE_SIZE - 1))
-		sz = -start & (PAGE_SIZE - 1);
-	else
-		sz = PAGE_SIZE;
+	sz = PAGE_SIZE - (start & (PAGE_SIZE - 1));
 
-	return min_t(unsigned long, sz, size);
+	return min(sz, size);
 }
 
 /*
@@ -137,9 +134,7 @@ static ssize_t read_mem(struct file * fi
 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 	/* we don't have page 0 mapped on sparc and m68k.. */
 	if (p < PAGE_SIZE) {
-		sz = PAGE_SIZE - p;
-		if (sz > count) 
-			sz = count; 
+		sz = size_inside_page(p, count);
 		if (sz > 0) {
 			if (clear_user(buf, sz))
 				return -EFAULT;
@@ -202,9 +197,7 @@ static ssize_t write_mem(struct file * f
 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 	/* we don't have page 0 mapped on sparc and m68k.. */
 	if (p < PAGE_SIZE) {
-		unsigned long sz = PAGE_SIZE - p;
-		if (sz > count)
-			sz = count;
+		sz = size_inside_page(p, count);
 		/* Hmm. Do something? */
 		buf += sz;
 		p += sz;
@@ -416,15 +409,14 @@ static ssize_t read_kmem(struct file *fi
 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 		/* we don't have page 0 mapped on sparc and m68k.. */
 		if (p < PAGE_SIZE && low_count > 0) {
-			size_t tmp = PAGE_SIZE - p;
-			if (tmp > low_count) tmp = low_count;
-			if (clear_user(buf, tmp))
+			sz = size_inside_page(p, low_count);
+			if (clear_user(buf, sz))
 				return -EFAULT;
-			buf += tmp;
-			p += tmp;
-			read += tmp;
-			low_count -= tmp;
-			count -= tmp;
+			buf += sz;
+			p += sz;
+			read += sz;
+			low_count -= sz;
+			count -= sz;
 		}
 #endif
 		while (low_count > 0) {
@@ -484,9 +476,7 @@ do_write_kmem(void *p, unsigned long rea
 #ifdef __ARCH_HAS_NO_PAGE_ZERO_MAPPED
 	/* we don't have page 0 mapped on sparc and m68k.. */
 	if (realp < PAGE_SIZE) {
-		unsigned long sz = PAGE_SIZE - realp;
-		if (sz > count)
-			sz = count;
+		sz = size_inside_page(realp, count);
 		/* Hmm. Do something? */
 		buf += sz;
 		p += sz;

-- 

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