[RFC][PATCH] kernel.h: Add generic roundup_64() macro

From: Steven Rostedt
Date: Thu May 23 2019 - 10:03:08 EST



From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

In discussing a build failure on x86_32 due to the use of roundup() on
a 64 bit number, I realized that there's no generic equivalent
roundup_64(). It is implemented in two separate places in the kernel,
but there really should be just one that all can use.

Although the other implementations are a static inline function, this
implementation is a macro to allow the use of typeof(x) to denote the
type that is being used. If the build is on a 64 bit machine, then the
roundup_64() macro will just default back to roundup(). But for 32 bit
machines, it will use the version that is will not cause issues with
dividing a 64 bit number on a 32 bit machine.

Link: http://lkml.kernel.org/r/20190522145450.25ff483d@xxxxxxxxxxxxxxxxxx

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index 34a998012bf6..cdacfe1f732c 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -143,14 +143,6 @@ nouveau_bo_del_ttm(struct ttm_buffer_object *bo)
kfree(nvbo);
}

-static inline u64
-roundup_64(u64 x, u32 y)
-{
- x += y - 1;
- do_div(x, y);
- return x * y;
-}
-
static void
nouveau_bo_fixup_align(struct nouveau_bo *nvbo, u32 flags,
int *align, u64 *size)
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index edbd5a210df2..13de9d49bd52 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -207,13 +207,6 @@ static inline xfs_dev_t linux_to_xfs_dev_t(dev_t dev)
#define xfs_sort(a,n,s,fn) sort(a,n,s,fn,NULL)
#define xfs_stack_trace() dump_stack()

-static inline uint64_t roundup_64(uint64_t x, uint32_t y)
-{
- x += y - 1;
- do_div(x, y);
- return x * y;
-}
-
static inline uint64_t howmany_64(uint64_t x, uint32_t y)
{
x += y - 1;
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 74b1ee9027f5..cd0063629357 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -115,6 +115,20 @@
(((x) + (__y - 1)) / __y) * __y; \
} \
)
+
+#if BITS_PER_LONG == 32
+# define roundup_64(x, y) ( \
+{ \
+ typeof(y) __y = y; \
+ typeof(x) __x = (x) + (__y - 1); \
+ do_div(__x, __y); \
+ __x * __y; \
+} \
+)
+#else
+# define roundup_64(x, y) roundup(x, y)
+#endif
+
/**
* rounddown - round down to next specified multiple
* @x: the value to round