Messages in this thread | | | Date | Mon, 24 Apr 2023 19:21:35 +0800 | Subject | Re: [PATCH v2 1/2] mm/page_alloc: drop the unnecessary pfn_valid() for start pfn | From | Baolin Wang <> |
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On 4/24/2023 6:54 PM, Michal Hocko wrote: > On Mon 24-04-23 18:46:40, Baolin Wang wrote: >> >> >> On 4/24/2023 5:50 PM, Michal Hocko wrote: >>> On Sun 23-04-23 18:59:10, Baolin Wang wrote: >>>> We've already used pfn_to_online_page() for start pfn to make sure >>> >>> Who is we? I do not see any note explicitly requiring that start_pfn has >>> to be valid for __pageblock_pfn_to_page. >> >> Sorry for confusing, what I mean is the __pageblock_pfn_to_page() function, >> which has used pfn_to_online_page() for start pfn. So the pfn_valid() in >> __pageblock_pfn_to_page() for start pfn is unnecessary. >> >> I will update the commit log to make it clear. > > Your comment suggested that the check _has_ already been done. Which is > not the case. pfn_to_online_page is called later in the function so I > guess you should rephrase as following: > > " > __pageblock_pfn_to_page currently performs both pfn_valid check and > pfn_to_online_page. The former one is redundant because the latter is a > stronger check. Drop pfn_valid. > "
Yes, will change the commit log.
> > With that or something going along with that. Feel free to add > Acked-by: Michal Hocko <mhocko@suse.com>
Thanks.
>>>> it is online and valid, so the pfn_valid() for the start pfn is >>>> unnecessary, drop it. >>>> >>>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> >>>> Reviewed-by: David Hildenbrand <david@redhat.com> >>>> Reviewed-by: "Huang, Ying" <ying.huang@intel.com> >>>> --- >>>> Changes from v1: >>>> - Collect reviewed tags. Thanks David and Ying. >>>> --- >>>> mm/page_alloc.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>> index 9de2a18519a1..6457b64fe562 100644 >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -1512,7 +1512,7 @@ struct page *__pageblock_pfn_to_page(unsigned long start_pfn, >>>> /* end_pfn is one past the range we are checking */ >>>> end_pfn--; >>>> - if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) >>>> + if (!pfn_valid(end_pfn)) >>>> return NULL; >>>> start_page = pfn_to_online_page(start_pfn); >>>> -- >>>> 2.27.0 >>> >
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