/dev/mem: make size_inside_page() logic straight

Also convert more size_inside_page() users.
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Avi Kivity <avi@qumranet.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/char/mem.c

@@ -39,12 +39,9 @@ static inline unsigned long size_inside_page(unsigned long start,
 {
 	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);
 }
 
 /*
@@ -139,9 +136,7 @@ static ssize_t read_mem(struct file * file, char __user * buf,
 #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;
@@ -201,9 +196,7 @@ static ssize_t write_mem(struct file * file, const char __user * buf,
 #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;
@@ -412,15 +405,14 @@ static ssize_t read_kmem(struct file *file, char __user *buf,
 #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) {
@@ -480,9 +472,7 @@ do_write_kmem(void *p, unsigned long realp, const char __user * buf,
 #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;