Re: [PATCH 3/7] arm: mm: accelerate pagefault when VM_FAULT_BADACCESS

[Suren Baghdasaryan]

On Tue, Apr 2, 2024 at 12:53 AM Kefeng Wang  wrote:
>
> The vm_flags of vma already checked under per-VMA lock, if it is a
> bad access, directly set fault to VM_FAULT_BADACCESS and handle error,
> so no need to lock_mm_and_find_vma() and check vm_flags again.
>
> Signed-off-by: Kefeng Wang 

Reviewed-by: Suren Baghdasaryan 



> ---
>  arch/arm/mm/fault.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
> index 439dc6a26bb9..5c4b417e24f9 100644
> --- a/arch/arm/mm/fault.c
> +++ b/arch/arm/mm/fault.c
> @@ -294,7 +294,9 @@ do_page_fault(unsigned long addr, unsigned int fsr, 
> struct pt_regs *regs)
>
> if (!(vma->vm_flags & vm_flags)) {
> vma_end_read(vma);
> -   goto lock_mmap;
> +   count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
> +   fault = VM_FAULT_BADACCESS;
> +   goto bad_area;
> }
> fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
> if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
> --
> 2.27.0
>

[PATCH 3/7] arm: mm: accelerate pagefault when VM_FAULT_BADACCESS

[Kefeng Wang]

The vm_flags of vma already checked under per-VMA lock, if it is a
bad access, directly set fault to VM_FAULT_BADACCESS and handle error,
so no need to lock_mm_and_find_vma() and check vm_flags again.

Signed-off-by: Kefeng Wang 
---
 arch/arm/mm/fault.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 439dc6a26bb9..5c4b417e24f9 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -294,7 +294,9 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct 
pt_regs *regs)
 
if (!(vma->vm_flags & vm_flags)) {
vma_end_read(vma);
-   goto lock_mmap;
+   count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
+   fault = VM_FAULT_BADACCESS;
+   goto bad_area;
}
fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
-- 
2.27.0