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Date:   Tue, 10 Oct 2023 14:30:19 -0700
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     Usama Arif <usama.arif@bytedance.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        akpm@linux-foundation.org, muchun.song@linux.dev,
        songmuchun@bytedance.com, fam.zheng@bytedance.com,
        liangma@liangbit.com, punit.agrawal@bytedance.com,
        Konrad Dybcio <konrad.dybcio@linaro.org>
Subject: Re: [External] Re: [PATCH] mm: hugetlb: Only prep and add allocated
 folios for non-gigantic pages
Message-ID: <20231010213019.GB279095@monkey>
References: <20231009145605.2150897-1-usama.arif@bytedance.com>
 <20231010012345.GA108129@monkey>
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On 10/10/23 18:01, Usama Arif wrote:
> 
> 
> On 10/10/2023 02:23, Mike Kravetz wrote:
> > On 10/09/23 15:56, Usama Arif wrote:
> > > Calling prep_and_add_allocated_folios when allocating gigantic pages
> > > at boot time causes the kernel to crash as folio_list is empty
> > > and iterating it causes a NULL pointer dereference. Call this only
> > > for non-gigantic pages when folio_list has entires.
> > 
> > Thanks!
> > 
> > However, are you sure the issue is the result of iterating through a
> > NULL list?  For reference, the routine prep_and_add_allocated_folios is:
> > 
> 
> Yes, you are right, it wasnt an issue with the list, but the lock. If I do
> the below diff it boots.

Thanks!

I believe that may be that may be the root cause of boot issues with
this series.  It is unfortunate that the failures were not consistent
and did not directly point at the root cause.

Hopefully, these changes will resolve the boot issues for Konrad as well.

I will create a new version of the "Batch hugetlb vmemmap modification
operations" series with these locking changes.
-- 
Mike Kravetz