* Re: + memblock-add-assertion-for-zero-allocation-alignment.patch added to -mm tree
[not found] <20130306224405.8160D5A4082@corp2gmr1-2.hot.corp.google.com>
@ 2013-03-07 0:07 ` Yinghai Lu
2013-03-07 0:16 ` Andrew Morton
2013-03-07 1:03 ` H. Peter Anvin
0 siblings, 2 replies; 3+ messages in thread
From: Yinghai Lu @ 2013-03-07 0:07 UTC (permalink / raw)
To: akpm, Linux Kernel Mailing List, H. Peter Anvin
Cc: mm-commits, Vineet.Gupta1, liwanp, mingo, tj, vgupta
On Wed, Mar 6, 2013 at 2:44 PM, <akpm@linux-foundation.org> wrote:
> ------------------------------------------------------
> From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
> Subject: memblock: add assertion for zero allocation alignment
>
> This came to light when calling memblock allocator from arc port (for
> copying flattended DT). If a "0" alignment is passed, the allocator
> round_up() call incorrectly rounds up the size to 0.
>
> round_up(num, alignto) => ((num - 1) | (alignto -1)) + 1
>
> While the obvious allocation failure causes kernel to panic, it is better
> to warn the caller to fix the code.
>
> Tejun suggested that instead of BUG_ON(!align) - which might be
> ineffective due to pending console init and such, it is better to WARN_ON,
> and continue the boot with a reasonable default align.
>
> Caller passing @size need not be handled similarly as the subsequent
> panic will indicate that anyhow.
>
> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
> Cc: Yinghai Lu <yinghai@kernel.org>
> Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Acked-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> mm/memblock.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff -puN mm/memblock.c~memblock-add-assertion-for-zero-allocation-alignment mm/memblock.c
> --- a/mm/memblock.c~memblock-add-assertion-for-zero-allocation-alignment
> +++ a/mm/memblock.c
> @@ -771,6 +771,9 @@ static phys_addr_t __init memblock_alloc
> {
> phys_addr_t found;
>
> + if (WARN_ON(!align))
> + align = __alignof__(long long);
> +
> /* align @size to avoid excessive fragmentation on reserved array */
> size = round_up(size, align);
Hi, Peter,
Do you agree that we should check align in round_up()?
Thanks
Yinghai
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: + memblock-add-assertion-for-zero-allocation-alignment.patch added to -mm tree
2013-03-07 0:07 ` + memblock-add-assertion-for-zero-allocation-alignment.patch added to -mm tree Yinghai Lu
@ 2013-03-07 0:16 ` Andrew Morton
2013-03-07 1:03 ` H. Peter Anvin
1 sibling, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2013-03-07 0:16 UTC (permalink / raw)
To: Yinghai Lu
Cc: Linux Kernel Mailing List, H. Peter Anvin, Vineet.Gupta1, liwanp,
mingo, tj, vgupta
On Wed, 6 Mar 2013 16:07:20 -0800 Yinghai Lu <yinghai@kernel.org> wrote:
> > --- a/mm/memblock.c~memblock-add-assertion-for-zero-allocation-alignment
> > +++ a/mm/memblock.c
> > @@ -771,6 +771,9 @@ static phys_addr_t __init memblock_alloc
> > {
> > phys_addr_t found;
> >
> > + if (WARN_ON(!align))
> > + align = __alignof__(long long);
> > +
> > /* align @size to avoid excessive fragmentation on reserved array */
> > size = round_up(size, align);
>
> Hi, Peter,
>
> Do you agree that we should check align in round_up()?
As you don't describe your reasoning it is hard to say.
But no, I don't think so. Checking for zero would add a pile of
basically useless code to the 100+ round_up() callsites, and
round_up(x, 0) is kinda meaningful, in a strange way.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: + memblock-add-assertion-for-zero-allocation-alignment.patch added to -mm tree
2013-03-07 0:07 ` + memblock-add-assertion-for-zero-allocation-alignment.patch added to -mm tree Yinghai Lu
2013-03-07 0:16 ` Andrew Morton
@ 2013-03-07 1:03 ` H. Peter Anvin
1 sibling, 0 replies; 3+ messages in thread
From: H. Peter Anvin @ 2013-03-07 1:03 UTC (permalink / raw)
To: Yinghai Lu
Cc: akpm, Linux Kernel Mailing List, mm-commits, Vineet.Gupta1,
liwanp, mingo, tj, vgupta
On 03/06/2013 04:07 PM, Yinghai Lu wrote:
>>
>> mm/memblock.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff -puN mm/memblock.c~memblock-add-assertion-for-zero-allocation-alignment mm/memblock.c
>> --- a/mm/memblock.c~memblock-add-assertion-for-zero-allocation-alignment
>> +++ a/mm/memblock.c
>> @@ -771,6 +771,9 @@ static phys_addr_t __init memblock_alloc
>> {
>> phys_addr_t found;
>>
>> + if (WARN_ON(!align))
>> + align = __alignof__(long long);
>> +
>> /* align @size to avoid excessive fragmentation on reserved array */
>> size = round_up(size, align);
>
> Hi, Peter,
>
> Do you agree that we should check align in round_up()?
>
Not in round_up(), that is used in way too many places. Doing it in
memblock_alloc() might make sense.
-hpa
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2013-03-07 1:05 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
[not found] <20130306224405.8160D5A4082@corp2gmr1-2.hot.corp.google.com>
2013-03-07 0:07 ` + memblock-add-assertion-for-zero-allocation-alignment.patch added to -mm tree Yinghai Lu
2013-03-07 0:16 ` Andrew Morton
2013-03-07 1:03 ` H. Peter Anvin
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).