linux-kernel - Re: [PATCH 1/3] mm: Call pointers to ptes as ptep

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Message-ID: <060ce34c-6729-4128-9190-264f7684e299@arm.com>
Date: Tue, 6 May 2025 17:22:39 +0530
From: Dev Jain <dev.jain@....com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: akpm@...ux-foundation.org, Liam.Howlett@...cle.com, vbabka@...e.cz,
 jannh@...gle.com, pfalcato@...e.de, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, david@...hat.com, peterx@...hat.com,
 ryan.roberts@....com, mingo@...nel.org, libang.li@...group.com,
 maobibo@...ngson.cn, zhengqi.arch@...edance.com, baohua@...nel.org,
 anshuman.khandual@....com, willy@...radead.org, ioworker0@...il.com,
 yang@...amperecomputing.com
Subject: Re: [PATCH 1/3] mm: Call pointers to ptes as ptep



On 06/05/25 4:22 pm, Lorenzo Stoakes wrote:
> On Tue, May 06, 2025 at 10:30:54AM +0530, Dev Jain wrote:
>> Avoid confusion between pte_t* and pte_t data types by appending pointer
>> type variables by p. No functional change.
> 
> NIT: 'appending'->'suffixing' and 'by p' -> with p'.

Thanks.

> 
>>
>> Signed-off-by: Dev Jain <dev.jain@....com>
> 
> This looks generally fine, could you fix the nit below however... sorry to
> be a pain!
> 
> Thanks!
> 
>> ---
>>   mm/mremap.c | 28 ++++++++++++++--------------
>>   1 file changed, 14 insertions(+), 14 deletions(-)
>>
>> diff --git a/mm/mremap.c b/mm/mremap.c
>> index 7db9da609c84..1a08a7c3b92f 100644
>> --- a/mm/mremap.c
>> +++ b/mm/mremap.c
>> @@ -176,7 +176,7 @@ static int move_ptes(struct pagetable_move_control *pmc,
>>   	struct vm_area_struct *vma = pmc->old;
>>   	bool need_clear_uffd_wp = vma_has_uffd_without_event_remap(vma);
>>   	struct mm_struct *mm = vma->vm_mm;
>> -	pte_t *old_pte, *new_pte, pte;
>> +	pte_t *old_ptep, *new_ptep, pte;
> 
> While we're at it, can we please move the pte decl to a new line? Mixing
> pointers and non-pointers is not great (I refactored it but mremap still
> has a bunch of less-than-ideal stuff in it :)

Sure.

> 
>>   	pmd_t dummy_pmdval;
>>   	spinlock_t *old_ptl, *new_ptl;
>>   	bool force_flush = false;
>> @@ -211,8 +211,8 @@ static int move_ptes(struct pagetable_move_control *pmc,
>>   	 * We don't have to worry about the ordering of src and dst
>>   	 * pte locks because exclusive mmap_lock prevents deadlock.
>>   	 */
>> -	old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
>> -	if (!old_pte) {
>> +	old_ptep = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
>> +	if (!old_ptep) {
>>   		err = -EAGAIN;
>>   		goto out;
>>   	}
>> @@ -223,10 +223,10 @@ static int move_ptes(struct pagetable_move_control *pmc,
>>   	 * mmap_lock, so this new_pte page is stable, so there is no need to get
>>   	 * pmdval and do pmd_same() check.
>>   	 */
>> -	new_pte = pte_offset_map_rw_nolock(mm, new_pmd, new_addr, &dummy_pmdval,
>> +	new_ptep = pte_offset_map_rw_nolock(mm, new_pmd, new_addr, &dummy_pmdval,
>>   					   &new_ptl);
>> -	if (!new_pte) {
>> -		pte_unmap_unlock(old_pte, old_ptl);
>> +	if (!new_ptep) {
>> +		pte_unmap_unlock(old_ptep, old_ptl);
>>   		err = -EAGAIN;
>>   		goto out;
>>   	}
>> @@ -235,12 +235,12 @@ static int move_ptes(struct pagetable_move_control *pmc,
>>   	flush_tlb_batched_pending(vma->vm_mm);
>>   	arch_enter_lazy_mmu_mode();
>>
>> -	for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
>> -				   new_pte++, new_addr += PAGE_SIZE) {
>> -		if (pte_none(ptep_get(old_pte)))
>> +	for (; old_addr < old_end; old_ptep++, old_addr += PAGE_SIZE,
>> +				   new_ptep++, new_addr += PAGE_SIZE) {
>> +		if (pte_none(ptep_get(old_ptep)))
>>   			continue;
>>
>> -		pte = ptep_get_and_clear(mm, old_addr, old_pte);
>> +		pte = ptep_get_and_clear(mm, old_addr, old_ptep);
>>   		/*
>>   		 * If we are remapping a valid PTE, make sure
>>   		 * to flush TLB before we drop the PTL for the
>> @@ -258,7 +258,7 @@ static int move_ptes(struct pagetable_move_control *pmc,
>>   		pte = move_soft_dirty_pte(pte);
>>
>>   		if (need_clear_uffd_wp && pte_marker_uffd_wp(pte))
>> -			pte_clear(mm, new_addr, new_pte);
>> +			pte_clear(mm, new_addr, new_ptep);
>>   		else {
>>   			if (need_clear_uffd_wp) {
>>   				if (pte_present(pte))
>> @@ -266,7 +266,7 @@ static int move_ptes(struct pagetable_move_control *pmc,
>>   				else if (is_swap_pte(pte))
>>   					pte = pte_swp_clear_uffd_wp(pte);
>>   			}
>> -			set_pte_at(mm, new_addr, new_pte, pte);
>> +			set_pte_at(mm, new_addr, new_ptep, pte);
>>   		}
>>   	}
>>
>> @@ -275,8 +275,8 @@ static int move_ptes(struct pagetable_move_control *pmc,
>>   		flush_tlb_range(vma, old_end - len, old_end);
>>   	if (new_ptl != old_ptl)
>>   		spin_unlock(new_ptl);
>> -	pte_unmap(new_pte - 1);
>> -	pte_unmap_unlock(old_pte - 1, old_ptl);
>> +	pte_unmap(new_ptep - 1);
>> +	pte_unmap_unlock(old_ptep - 1, old_ptl);
>>   out:
>>   	if (pmc->need_rmap_locks)
>>   		drop_rmap_locks(vma);
>> --
>> 2.30.2
>>