linux-kernel - [PATCH] kernel: rounddown helper function

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Message-ID: <20100803181607.30614.36916.stgit@paris.rdu.redhat.com>
Date:	Tue, 03 Aug 2010 14:16:07 -0400
From:	Eric Paris <eparis@...hat.com>
To:	linux-kernel@...r.kernel.org, selinux@...ho.nsa.gov
Cc:	akpm@...ux-foundation.org, sds@...ho.nsa.gov, jmorris@...ei.org
Subject: [PATCH] kernel: rounddown helper function

The roundup() helper function will round a given value up to a multiple of
another given value.  aka  roundup(11, 7) would give 14 = 7 * 2.  This new
function does the opposite.  It will round a given number down to the
nearest multiple of the second number: rounddown(11, 7) would give 7.

I need this in some future SELinux code and can carry the macro myself, but
figured I would put it in the core kernel so others might find and use it
if need be.

Signed-off-by: Eric Paris <eparis@...hat.com>
---

 include/linux/kernel.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 7d5b10f..d6092fd 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -59,6 +59,7 @@ extern const char linux_proc_banner[];
 #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f))
 #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
 #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
+#define rounddown(x, y) ((x) - ((x) % (y)))
 #define DIV_ROUND_CLOSEST(x, divisor)(			\
 {							\
 	typeof(divisor) __divisor = divisor;		\

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