[PATCH 06/14] mm: handle_pte_fault() use pte_offset_map_maywrite_nolock()

[LEROY Christophe]

Le 21/08/2024 à 10:18, Qi Zheng a écrit :
> In handle_pte_fault(), we may modify the vmf->pte after acquiring the
> vmf->ptl, so convert it to using pte_offset_map_maywrite_nolock(). But
> since we already do the pte_same() check, so there is no need to get
> pmdval to do pmd_same() check, just pass NULL to pmdvalp parameter.
> 
> Signed-off-by: Qi Zheng <zhengqi.arch at bytedance.com>
> ---
>   mm/memory.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 93c0c25433d02..d3378e98faf13 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -5504,9 +5504,14 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
>   		 * pmd by anon khugepaged, since that takes mmap_lock in write
>   		 * mode; but shmem or file collapse to THP could still morph
>   		 * it into a huge pmd: just retry later if so.
> +		 *
> +		 * Use the maywrite version to indicate that vmf->pte will be
> +		 * modified, but since we will use pte_same() to detect the
> +		 * change of the pte entry, there is no need to get pmdval.
>   		 */
> -		vmf->pte = pte_offset_map_nolock(vmf->vma->vm_mm, vmf->pmd,
> -						 vmf->address, &vmf->ptl);
> +		vmf->pte = pte_offset_map_maywrite_nolock(vmf->vma->vm_mm,
> +							  vmf->pmd, vmf->address,
> +							  NULL, &vmf->ptl);

This might be the demonstration that the function name is becoming too long.

Can you find shorter names ?

>   		if (unlikely(!vmf->pte))
>   			return 0;
>   		vmf->orig_pte = ptep_get_lockless(vmf->pte);