patch "devres: Align data[] to ARCH_KMALLOC_MINALIGN" added to driver-core-linus - Linux-stable-mirror

11 Nov 2018

This is a note to let you know that I've just added the patch titled
devres: Align data[] to ARCH_KMALLOC_MINALIGN
to my driver-core git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
in the driver-core-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
...
From a66d972465d15b1d89281258805eb8b47d66bd36 Mon Sep 17 00:00:00 2001
From: Alexey Brodkin alexey.brodkin@synopsys.com
Date: Wed, 31 Oct 2018 18:25:47 +0300
Subject: devres: Align data[] to ARCH_KMALLOC_MINALIGN
Initially we bumped into problem with 32-bit aligned atomic64_t
on ARC, see [1]. And then during quite lengthly discussion Peter Z.
mentioned ARCH_KMALLOC_MINALIGN which IMHO makes perfect sense.
If allocation is done by plain kmalloc() obtained buffer will be
ARCH_KMALLOC_MINALIGN aligned and then why buffer obtained via
devm_kmalloc() should have any other alignment?
This way we at least get the same behavior for both types of
allocation.
[1] http://lists.infradead.org/pipermail/linux-snps-arc/2018-July/004009.html
[2] http://lists.infradead.org/pipermail/linux-snps-arc/2018-July/004036.html
Signed-off-by: Alexey Brodkin abrodkin@synopsys.com
Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org
Cc: Geert Uytterhoeven geert@linux-m68k.org
Cc: David Laight David.Laight@ACULAB.COM
Cc: Peter Zijlstra peterz@infradead.org
Cc: Thomas Gleixner tglx@linutronix.de
Cc: Vineet Gupta vgupta@synopsys.com
Cc: Will Deacon will.deacon@arm.com
Cc: Greg KH greg@kroah.com
Cc: stable@vger.kernel.org # 4.8+
Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
---
 drivers/base/devres.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 4aaf00d2098b..e038e2b3b7ea 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -26,8 +26,14 @@ struct devres_node {
struct devres {
    struct devres_node		node;
-	/* -- 3 pointers */
-	unsigned long long		data[];	/* guarantee ull alignment */
+	/*
+	 * Some archs want to perform DMA into kmalloc caches
+	 * and need a guaranteed alignment larger than
+	 * the alignment of a 64-bit integer.
+	 * Thus we use ARCH_KMALLOC_MINALIGN here and get exactly the same
+	 * buffer alignment as if it was allocated by plain kmalloc().
+	 */
+	u8 __aligned(ARCH_KMALLOC_MINALIGN) data[];
 };
struct devres_group {
-- 
2.19.1



    