From: Olav Haugan <ohaugan@codeaurora.org>
To: Nitin Gupta <ngupta@vflare.org>,
David Cohen <david.a.cohen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Seth Jennings <sjenning@linux.vnet.ibm.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Minchan Kim <minchan@kernel.org>,
linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH] staging: zsmalloc: Ensure handle is never 0 on success
Date: Wed, 06 Nov 2013 15:46:42 -0800 [thread overview]
Message-ID: <527AD4E2.6080706@codeaurora.org> (raw)
In-Reply-To: <CAPkvG_ftpPJMdYdOmKdYT2e6sd+tntX_vrvpLbAW85dXYJiQdw@mail.gmail.com>
On 11/6/2013 12:56 PM, Nitin Gupta wrote:
> On Tue, Nov 5, 2013 at 5:17 PM, David Cohen
> <david.a.cohen@linux.intel.com> wrote:
>> Hi Olav,
>>
>>
>> On 11/05/2013 04:54 PM, Olav Haugan wrote:
>>>
>>> zsmalloc encodes a handle using the page pfn and an object
>>> index. On some hardware platforms the pfn could be 0 and this
>>> causes the encoded handle to be 0 which is interpreted as an
>>> allocation failure.
>>>
>>> To prevent this false error we ensure that the encoded handle
>>> will not be 0 when allocation succeeds.
>>>
>>> Change-Id: Ifff930dcf254915b497aec5cb36f152a5e5365d6
>>> Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
>>> ---
>>> drivers/staging/zsmalloc/zsmalloc-main.c | 4 ++--
>>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c
>>> b/drivers/staging/zsmalloc/zsmalloc-main.c
>>> index 523b937..0e32c0f 100644
>>> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
>>> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
>>> @@ -441,7 +441,7 @@ static void *obj_location_to_handle(struct page *page,
>>> unsigned long obj_idx)
>>> }
>>>
>>> handle = page_to_pfn(page) << OBJ_INDEX_BITS;
>>> - handle |= (obj_idx & OBJ_INDEX_MASK);
>>> + handle |= ((obj_idx + 1) & OBJ_INDEX_MASK);
>>
>>
>> As suggestion you could use a macro instead of hardcoded 1.
>>
>> I am not familiar with this code, but if it's a valid test to verify if
>> the resulting address is page aligned, you might want to set this
>> offset macro to a page aligned value as well.
>>
>>
>
> Using a hardcoded 1 looks fine in this case. But the patch description
> should also be added as a comment for this function. Otherwise, the patch
> looks good to me.
>
Sure, I can add a comment above obj_location_to_handle() and
obj_handle_to_location().
Olav Haugan
--
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
next prev parent reply other threads:[~2013-11-06 23:46 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-06 0:54 [PATCH] staging: zsmalloc: Ensure handle is never 0 on success Olav Haugan
2013-11-06 1:17 ` David Cohen
2013-11-06 20:56 ` Nitin Gupta
2013-11-06 23:46 ` Olav Haugan [this message]
2013-11-06 1:56 ` Greg KH
2013-11-06 21:09 ` Nitin Gupta
2013-11-06 22:10 ` Greg KH
2013-11-06 23:46 ` Nitin Gupta
2013-11-07 3:05 ` Greg KH
2013-11-07 0:00 ` Olav Haugan
2013-11-07 3:06 ` Greg KH
2013-11-07 22:57 ` Olav Haugan
2013-11-07 7:04 Minchan Kim
2013-11-07 17:06 ` Luigi Semenzato
2013-11-07 17:36 ` Luigi Semenzato
2013-11-08 2:02 ` Greg KH
2013-11-07 17:10 ` Rik van Riel
2013-11-08 10:44 ` Bob Liu
2013-11-12 15:41 ` Minchan Kim
2013-11-13 2:42 ` Greg KH
2013-11-13 6:24 ` Nitin Gupta
2013-11-14 4:00 ` Hugh Dickins
2013-11-14 16:21 ` Seth Jennings
2013-11-15 0:47 ` Bob Liu
2013-11-15 0:31 ` Minchan Kim
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