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

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Message-ID: <5c20ada8-4863-4a33-bb1d-3b5695d0bf66@lucifer.local>
Date: Tue, 6 May 2025 11:52:50 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Dev Jain <dev.jain@....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 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'.

>
> 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 :)

>  	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
>