Re: [PATCH 1/6] nommu: sort mm->mmap list properly

[Namhyung Kim]

2011-03-31 (ë), 11:51 -0700, Andrew Morton:
> On Mon, 28 Mar 2011 22:56:42 +0900
> Namhyung Kim <namhyung@xxxxxxxxx> wrote:
> 
> > @vma added into @mm should be sorted by start addr, end addr and VMA struct
> > addr in that order because we may get identical VMAs in the @mm. However
> > this was true only for the rbtree, not for the list.
> > 
> > This patch fixes this by remembering 'rb_prev' during the tree traversal
> > like find_vma_prepare() does and linking the @vma via __vma_link_list().
> > After this patch, we can iterate the whole VMAs in correct order simply
> > by using @mm->mmap list.
> > 
> > Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxx>
> > ---
> >  mm/nommu.c |   62 ++++++++++++++++++++++++++++++++++++++---------------------
> >  1 files changed, 40 insertions(+), 22 deletions(-)
> > 
> > diff --git a/mm/nommu.c b/mm/nommu.c
> > index e7dbd3fae187..20d9c330eb0e 100644
> > --- a/mm/nommu.c
> > +++ b/mm/nommu.c
> > @@ -672,6 +672,30 @@ static void protect_vma(struct vm_area_struct *vma, unsigned long flags)
> >  #endif
> >  }
> >  
> > +/* borrowed from mm/mmap.c */
> > +static inline void
> > +__vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
> > +		struct vm_area_struct *prev, struct rb_node *rb_parent)
> > +{
> > +	struct vm_area_struct *next;
> > +
> > +	vma->vm_prev = prev;
> > +	if (prev) {
> > +		next = prev->vm_next;
> > +		prev->vm_next = vma;
> > +	} else {
> > +		mm->mmap = vma;
> > +		if (rb_parent)
> > +			next = rb_entry(rb_parent,
> > +					struct vm_area_struct, vm_rb);
> > +		else
> > +			next = NULL;
> > +	}
> > +	vma->vm_next = next;
> > +	if (next)
> > +		next->vm_prev = vma;
> > +}
> 
> Duplicating code is rather bad.  And putting random vma functions into
> mm/util.c is pretty ugly too, but I suppose it's less bad.
> 

Agreed. Thanks for doing this.


>  mm/internal.h |    4 ++++
>  mm/mmap.c     |   22 ----------------------
>  mm/nommu.c    |   24 ------------------------
>  mm/util.c     |   24 ++++++++++++++++++++++++
>  4 files changed, 28 insertions(+), 46 deletions(-)
> 
> diff -puN mm/nommu.c~mm-nommu-sort-mm-mmap-list-properly-fix mm/nommu.c
> --- a/mm/nommu.c~mm-nommu-sort-mm-mmap-list-properly-fix
> +++ a/mm/nommu.c
> @@ -672,30 +672,6 @@ static void protect_vma(struct vm_area_s
>  #endif
>  }
>  
> -/* borrowed from mm/mmap.c */
> -static inline void
> -__vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
> -		struct vm_area_struct *prev, struct rb_node *rb_parent)
> -{
> -	struct vm_area_struct *next;
> -
> -	vma->vm_prev = prev;
> -	if (prev) {
> -		next = prev->vm_next;
> -		prev->vm_next = vma;
> -	} else {
> -		mm->mmap = vma;
> -		if (rb_parent)
> -			next = rb_entry(rb_parent,
> -					struct vm_area_struct, vm_rb);
> -		else
> -			next = NULL;
> -	}
> -	vma->vm_next = next;
> -	if (next)
> -		next->vm_prev = vma;
> -}
> -
>  /*
>   * add a VMA into a process's mm_struct in the appropriate place in the list
>   * and tree and add to the address space's page tree also if not an anonymous
> diff -puN mm/util.c~mm-nommu-sort-mm-mmap-list-properly-fix mm/util.c
> --- a/mm/util.c~mm-nommu-sort-mm-mmap-list-properly-fix
> +++ a/mm/util.c
> @@ -6,6 +6,8 @@
>  #include <linux/sched.h>
>  #include <asm/uaccess.h>
>  
> +#include "internal.h"
> +
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/kmem.h>
>  
> @@ -215,6 +217,28 @@ char *strndup_user(const char __user *s,
>  }
>  EXPORT_SYMBOL(strndup_user);
>  
> +void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
> +		struct vm_area_struct *prev, struct rb_node *rb_parent)
> +{
> +	struct vm_area_struct *next;
> +
> +	vma->vm_prev = prev;
> +	if (prev) {
> +		next = prev->vm_next;
> +		prev->vm_next = vma;
> +	} else {
> +		mm->mmap = vma;
> +		if (rb_parent)
> +			next = rb_entry(rb_parent,
> +					struct vm_area_struct, vm_rb);
> +		else
> +			next = NULL;
> +	}
> +	vma->vm_next = next;
> +	if (next)
> +		next->vm_prev = vma;
> +}
> +
>  #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
>  void arch_pick_mmap_layout(struct mm_struct *mm)
>  {
> diff -puN mm/internal.h~mm-nommu-sort-mm-mmap-list-properly-fix mm/internal.h
> --- a/mm/internal.h~mm-nommu-sort-mm-mmap-list-properly-fix
> +++ a/mm/internal.h
> @@ -66,6 +66,10 @@ static inline unsigned long page_order(s
>  	return page_private(page);
>  }
>  
> +/* mm/util.c */
> +void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
> +		struct vm_area_struct *prev, struct rb_node *rb_parent);
> +
>  #ifdef CONFIG_MMU
>  extern long mlock_vma_pages_range(struct vm_area_struct *vma,
>  			unsigned long start, unsigned long end);
> diff -puN mm/mmap.c~mm-nommu-sort-mm-mmap-list-properly-fix mm/mmap.c
> --- a/mm/mmap.c~mm-nommu-sort-mm-mmap-list-properly-fix
> +++ a/mm/mmap.c
> @@ -398,28 +398,6 @@ find_vma_prepare(struct mm_struct *mm, u
>  	return vma;
>  }
>  
> -void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
> -		struct vm_area_struct *prev, struct rb_node *rb_parent)
> -{
> -	struct vm_area_struct *next;
> -
> -	vma->vm_prev = prev;
> -	if (prev) {
> -		next = prev->vm_next;
> -		prev->vm_next = vma;
> -	} else {
> -		mm->mmap = vma;
> -		if (rb_parent)
> -			next = rb_entry(rb_parent,
> -					struct vm_area_struct, vm_rb);
> -		else
> -			next = NULL;
> -	}
> -	vma->vm_next = next;
> -	if (next)
> -		next->vm_prev = vma;
> -}
> -
>  void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
>  		struct rb_node **rb_link, struct rb_node *rb_parent)
>  {
> _
> 
> 


-- 
Regards,
Namhyung Kim


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