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Message-ID: <e6801255-238d-5c16-fe65-945de10952ce@nvidia.com>
Date:   Fri, 30 Jun 2023 17:21:56 -0700
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Subject: Re: [PATCH] mm/hugetlb.c: fix a bug within a BUG(): inconsistent pte
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To:     Ryan Roberts <ryan.roberts@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>
CC:     LKML <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
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References: <20230630013203.1955064-1-jhubbard@nvidia.com>
 <05ea6668-3dca-23ed-56c8-bbf8079d93cd@arm.com>
From:   John Hubbard <jhubbard@nvidia.com>
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On 6/30/23 03:07, Ryan Roberts wrote:
...
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index bce28cca73a1..73fbeb8f979f 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -7246,7 +7246,12 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
>>   				pte = (pte_t *)pmd_alloc(mm, pud, addr);
>>   		}
>>   	}
>> -	BUG_ON(pte && pte_present(ptep_get(pte)) && !pte_huge(ptep_get(pte)));
>> +
>> +	if (pte) {
>> +		pte_t pteval = ptep_get(pte);
> 
> Given the PTL is not held here, I think this should technically be
> ptep_get_lockless()?
> 

Oh yes. I'll change it to that and send a v2, thanks!


thanks,
-- 
John Hubbard
NVIDIA