kernel.h: drop inclusion in bitmap.h

The bitmap.h header is used in a lot of code around the kernel.  Besides
that it includes kernel.h which sometimes makes a loop.

The problem here is many unneeded loops that make header hell
dependencies.  For example, how may you move bitmap_zalloc() from C-file
to the header?  Currently it's impossible.  And bitmap.h here is only the
tip of an iceberg.

kerne.h is a dump of everything that even has nothing in common at all.
We may still have it, but in my new code I prefer to include only the
headers that I want to use, without the bulk of unneeded kernel code.

Break the loop by introducing align.h, including it in kernel.h and
bitmap.h followed by replacing kernel.h with limits.h.

Link: https://lkml.kernel.org/r/20210326170347.37441-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/align.h

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_ALIGN_H
+#define _LINUX_ALIGN_H
+
+#include <linux/const.h>
+
+/* @a is a power of 2 value */
+#define ALIGN(x, a)		__ALIGN_KERNEL((x), (a))
+#define ALIGN_DOWN(x, a)	__ALIGN_KERNEL((x) - ((a) - 1), (a))
+#define __ALIGN_MASK(x, mask)	__ALIGN_KERNEL_MASK((x), (mask))
+#define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
+#define PTR_ALIGN_DOWN(p, a)	((typeof(p))ALIGN_DOWN((unsigned long)(p), (a)))
+#define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
+
+#endif	/* _LINUX_ALIGN_H */

include/linux/bitmap.h

@@ -4,10 +4,11 @@
 
 #ifndef __ASSEMBLY__
 
+#include <linux/align.h>
 #include <linux/types.h>
 #include <linux/bitops.h>
+#include <linux/limits.h>
 #include <linux/string.h>
-#include <linux/kernel.h>
 
 /*
  * bitmaps provide bit arrays that consume one or more unsigned

include/linux/kernel.h

@@ -3,6 +3,7 @@
 #define _LINUX_KERNEL_H
 
 #include <stdarg.h>
+#include <linux/align.h>
 #include <linux/limits.h>
 #include <linux/linkage.h>
 #include <linux/stddef.h>
@@ -30,14 +31,6 @@
  */
 #define REPEAT_BYTE(x)	((~0ul / 0xff) * (x))
 
-/* @a is a power of 2 value */
-#define ALIGN(x, a)		__ALIGN_KERNEL((x), (a))
-#define ALIGN_DOWN(x, a)	__ALIGN_KERNEL((x) - ((a) - 1), (a))
-#define __ALIGN_MASK(x, mask)	__ALIGN_KERNEL_MASK((x), (mask))
-#define PTR_ALIGN(p, a)		((typeof(p))ALIGN((unsigned long)(p), (a)))
-#define PTR_ALIGN_DOWN(p, a)	((typeof(p))ALIGN_DOWN((unsigned long)(p), (a)))
-#define IS_ALIGNED(x, a)		(((x) & ((typeof(x))(a) - 1)) == 0)
-
 /* generic data direction definitions */
 #define READ			0
 #define WRITE			1