linux-kernel - Re: [RFC PATCH] device: Add kernel standard devm

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Message-ID: <8761stu7rl.fsf@linaro.org>
Date:	Fri, 18 Oct 2013 22:52:46 -0700
From:	Kevin Hilman <khilman@...aro.org>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Joe Perches <joe@...ches.com>, Tejun Heo <tj@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Sangjung Woo <sangjung.woo@...sung.com>,
	Olof Johansson <olof@...om.net>,
	Thierry Reding <thierry.reding@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH] device: Add kernel standard devm_k.alloc functions

Greg KH <gregkh@...uxfoundation.org> writes:

> On Fri, Oct 18, 2013 at 10:04:11AM -0700, Kevin Hilman wrote:
>> > A handful of boot panics on ARM platforms were bisected to point at
>> > the version of this commit that's in linux-next (commit
>> > 64c862a839a8db2c02bbaa88b923d13e1208919d).  Reverting this commit
>> > makes things happy again.
>> >
>> > Upon further digging, it seems that users of devres_alloc() are
>> > relying on the previous behavior of having the memory zero'd which is
>> > no longer the case after $SUBJECT patch.  The change below on top of
>> > -next makes these ARM boards happy again.
>> 
>> Oops, it should've fixed __devres_alloc() also.  Updated patch below.
>
> Can you send this in a format that I can apply it in?  It was whitespace
> damaged.

hmm, sorry about that.  This one should work, though I wonder if Andrew
should pick this up since I think the patch that causes the breakage
came through his tree.

Kevin

---------------8<----------------------------------------------------
>From a1962ed4a999fb630a48f75a5ecaf84401d5dbfc Mon Sep 17 00:00:00 2001
From: Kevin Hilman <khilman@...aro.org>
Date: Fri, 18 Oct 2013 09:41:39 -0700
Subject: [PATCH] devres: restore zeroing behavior of devres_alloc()

commit 64c862a8 (devres: add kernel standard devm_k.alloc functions) changed
the default behavior of alloc_dr() to no longer zero the allocated memory.  However,
only the devm.k.alloc() function were modified to pass in __GFP_ZERO which leaves
any users of devres_alloc() or __devres_alloc() with potentially wrong assumptions
about memory being zero'd upon allocation.

To fix, add __GFP_ZERO to devres_alloc() calls to preserve previous
behavior of zero'ing memory upon allocation.

Signed-off-by: Kevin Hilman <khilman@...aro.org>
---
 drivers/base/devres.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 37e67a2..545c4de 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -111,7 +111,7 @@ void * __devres_alloc(dr_release_t release, size_t size, gfp_t gfp,
 {
 	struct devres *dr;
 
-	dr = alloc_dr(release, size, gfp);
+	dr = alloc_dr(release, size, gfp | __GFP_ZERO);
 	if (unlikely(!dr))
 		return NULL;
 	set_node_dbginfo(&dr->node, name, size);
@@ -136,7 +136,7 @@ void * devres_alloc(dr_release_t release, size_t size, gfp_t gfp)
 {
 	struct devres *dr;
 
-	dr = alloc_dr(release, size, gfp);
+	dr = alloc_dr(release, size, gfp | __GFP_ZERO);
 	if (unlikely(!dr))
 		return NULL;
 	return dr->data;
-- 
1.8.3

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