On 21 Jun 2017, at 7:49, Kirill A. Shutemov wrote: > On Tue, Jun 20, 2017 at 07:07:11PM -0400, Zi Yan wrote: >> @@ -1220,6 +1238,9 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t >> orig_pmd) >> if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) >> goto out_unlock; >> >> + if (unlikely(!pmd_present(orig_pmd))) >> + goto out_unlock; >> + > > Hm. Shouldn't we wait for the page here?
Thanks for pointing this out.
This chunk is unnecessary, since do_huge_pmd_wp_page() is called by
wp_huge_pmd(),
which is called only when orig_pmd is present. Thus, this code is useless.
And pmd_same() will also preclude vmf->pmd from not present.
>> page = pmd_page(orig_pmd);
>> VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
>> /*
>> @@ -1556,6 +1577,12 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb,
>> struct vm_area_struct *vma,
>> if (is_huge_zero_pmd(orig_pmd))
>> goto out;
>>
>> + if (unlikely(!pmd_present(orig_pmd))) {
>> + VM_BUG_ON(IS_ENABLED(CONFIG_MIGRATION) &&
>> + !is_pmd_migration_entry(orig_pmd));
>> + goto out;
>> + }
>> +
>> page = pmd_page(orig_pmd);
>> /*
>> * If other processes are mapping this page, we couldn't discard
>> @@ -1770,6 +1797,23 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t
>> *pmd,
>> preserve_write = prot_numa && pmd_write(*pmd);
>> ret = 1;
>>
>> +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
>> + if (is_swap_pmd(*pmd)) {
>> + swp_entry_t entry = pmd_to_swp_entry(*pmd);
>> +
>> + VM_BUG_ON(IS_ENABLED(CONFIG_MIGRATION) &&
>> + !is_pmd_migration_entry(*pmd));
>> + if (is_write_migration_entry(entry)) {
>> + pmd_t newpmd;
>> +
>> + make_migration_entry_read(&entry);
>> + newpmd = swp_entry_to_pmd(entry);
>> + set_pmd_at(mm, addr, pmd, newpmd);
>
> I was confused by this. Could you copy comment from change_pte_range()
> here?
Sure. Will do.
>> + }
>> + goto unlock;
>> + }
>> +#endif
>> +
>> /*
>> * Avoid trapping faults against the zero page. The read-only
>> * data is likely to be read-cached on the local CPU and
Thanks for your review.
--
Best Regards
Yan Zi
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