linux-kernel - Re: [PATCH v3 29/30] luo: allow preserving memfd

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Message-ID: <mafs0o6sjwfvw.fsf@kernel.org>
Date: Wed, 13 Aug 2025 14:44:03 +0200
From: Pratyush Yadav <pratyush@...nel.org>
To: Pasha Tatashin <pasha.tatashin@...een.com>
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Subject: Re: [PATCH v3 29/30] luo: allow preserving memfd

On Fri, Aug 08 2025, Pasha Tatashin wrote:

>> +static int memfd_luo_preserve_folios(struct memfd_luo_preserved_folio *pfolios,
>> +                                    struct folio **folios,
>> +                                    unsigned int nr_folios)
>> +{
>> +       unsigned int i;
>
> Should be 'long i'
>
> Otherwise in err_unpreserve we get into an infinite loop. Thank you
> Josh Hilke for noticing this.

Good catch! Will fix.
>
>> +       int err;
>> +
>> +       for (i = 0; i < nr_folios; i++) {
>> +               struct memfd_luo_preserved_folio *pfolio = &pfolios[i];
>> +               struct folio *folio = folios[i];
>> +               unsigned int flags = 0;
>> +               unsigned long pfn;
>> +
>> +               err = kho_preserve_folio(folio);
>> +               if (err)
>> +                       goto err_unpreserve;
>> +
>> +               pfn = folio_pfn(folio);
>> +               if (folio_test_dirty(folio))
>> +                       flags |= PRESERVED_FLAG_DIRTY;
>> +               if (folio_test_uptodate(folio))
>> +                       flags |= PRESERVED_FLAG_UPTODATE;
>> +
>> +               pfolio->foliodesc = PRESERVED_FOLIO_MKDESC(pfn, flags);
>> +               pfolio->index = folio->index;
>> +       }
>> +
>> +       return 0;
>> +
>> +err_unpreserve:
>> +       i--;
>> +       for (; i >= 0; i--)
>> +               WARN_ON_ONCE(kho_unpreserve_folio(folios[i]));
>> +       return err;
>> +}
>> +

-- 
Regards,
Pratyush Yadav