Subject: Re: [RESEND PATCH v3 1/2] mm: Introducing arch_remap hook

From: "Kirill A. Shutemov" <[email-masked]>
Date: Mon, 13 Apr 2015 14:58:11 +0300

On Mon, Apr 13, 2015 at 11:56:27AM +0200, Laurent Dufour wrote:
> Some architecture would like to be triggered when a memory area is moved
> through the mremap system call.
> 
> This patch is introducing a new arch_remap mm hook which is placed in the
> path of mremap, and is called before the old area is unmapped (and the
> arch_unmap hook is called).
> 
> The architectures which need to call this hook should define
> __HAVE_ARCH_REMAP in their asm/mmu_context.h and provide the arch_remap
> service with the following prototype:
> void arch_remap(struct mm_struct *mm,
>                 unsigned long old_start, unsigned long old_end,
>                 unsigned long new_start, unsigned long new_end);
> 
> Signed-off-by: Laurent Dufour <[email-masked]>
> Reviewed-by: Ingo Molnar <[email-masked]>
> ---
>  mm/mremap.c | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/mremap.c b/mm/mremap.c
> index 2dc44b1cb1df..009db5565893 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -25,6 +25,7 @@
>  
>  #include <asm/cacheflush.h>
>  #include <asm/tlbflush.h>
> +#include <asm/mmu_context.h>
>  
>  #include "internal.h"
>  
> @@ -286,13 +287,19 @@ static unsigned long move_vma(struct vm_area_struct *vma,
>  		old_len = new_len;
>  		old_addr = new_addr;
>  		new_addr = -ENOMEM;
> -	} else if (vma->vm_file && vma->vm_file->f_op->mremap) {
> -		err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma);
> -		if (err < 0) {
> -			move_page_tables(new_vma, new_addr, vma, old_addr,
> -					 moved_len, true);
> -			return err;
> +	} else {
> +		if (vma->vm_file && vma->vm_file->f_op->mremap) {
> +			err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma);
> +			if (err < 0) {
> +				move_page_tables(new_vma, new_addr, vma,
> +						  old_addr, moved_len, true);
> +				return err;
> +			}
>  		}
> +#ifdef __HAVE_ARCH_REMAP

It would be cleaner to provide dummy arch_remap() for !__HAVE_ARCH_REMAP
in some generic header.

> +		arch_remap(mm, old_addr, old_addr+old_len,
> +			   new_addr, new_addr+new_len);

Spaces around '+'?

> +#endif
>  	}
>  
>  	/* Conceal VM_ACCOUNT so old reservation is not undone */
> -- 
> 1.9.1
> 
> --
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-- 
 Kirill A. Shutemov