On Fri, 14 Apr 2011, Michal Hocko wrote:
> Hi,
> the following patch is just a cleanup for better readability without any
> functional changes. What do you think about it?
> ---
> From 71de71aaa725ee87459b3a256e8bb0af7de4abeb Mon Sep 17 00:00:00 2001
> From: Michal Hocko <mhocko@xxxxxxx>
> Date: Fri, 15 Apr 2011 14:56:26 +0200
> Subject: [PATCH] mm: make expand_downwards symmetrical to expand_upwards
>
> Currently we have expand_upwards exported while expand_downwards is
> accessible only via expand_stack.
>
> check_stack_guard_page is a nice example of the asymmetry. It uses
> expand_stack for VM_GROWSDOWN while expand_upwards is called for
> VM_GROWSUP case. Let's make this consistent and export expand_downwards
> same way we do with expand_upwards.
>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Yes, I've just been looking around here, and I like your symmetry.
But two points:
> ---
> include/linux/mm.h | 2 ++
> mm/memory.c | 2 +-
> mm/mmap.c | 2 +-
> 3 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 692dbae..765cf4e 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1498,8 +1498,10 @@ unsigned long ra_submit(struct file_ra_state *ra,
> extern int expand_stack(struct vm_area_struct *vma, unsigned long address);
> #if VM_GROWSUP
> extern int expand_upwards(struct vm_area_struct *vma, unsigned long address);
> + #define expand_downwards(vma, address) do { } while (0)
I think this is wrong: doesn't the VM_GROWSUP case actually want
a real expand_downwards() in addition to expand_upwards()?
> #else
> #define expand_upwards(vma, address) do { } while (0)
> +extern int expand_downwards(struct vm_area_struct *vma, unsigned long address);
> #endif
> extern int expand_stack_downwards(struct vm_area_struct *vma,
> unsigned long address);
And if you're going for symmetry, wouldn't it be nice to add fs/exec.c
to the patch and remove this silly expand_stack_downwards() wrapper?
Hugh
> diff --git a/mm/memory.c b/mm/memory.c
> index ce22a25..f404fb6 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2969,7 +2969,7 @@ static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned lo
> if (prev && prev->vm_end == address)
> return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
>
> - expand_stack(vma, address - PAGE_SIZE);
> + expand_downwards(vma, address - PAGE_SIZE);
> }
> if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
> struct vm_area_struct *next = vma->vm_next;
> diff --git a/mm/mmap.c b/mm/mmap.c
> index e27e0cf..6b2a817 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1782,7 +1782,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
> /*
> * vma is the first one with address < vma->vm_start. Have to extend vma.
> */
> -static int expand_downwards(struct vm_area_struct *vma,
> +int expand_downwards(struct vm_area_struct *vma,
> unsigned long address)
> {
> int error;
> --
> 1.7.4.1
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>