Messages in this thread | | | Date | Sun, 17 Apr 2011 20:00:17 -0700 (PDT) | From | Hugh Dickins <> | Subject | Re: [PATCH] mm: make expand_downwards symmetrical to expand_upwards |
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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@suse.cz> > 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@suse.cz>
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
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