[Xen-devel] Ping: [PATCH] fix off-by-one mistakes in vm_alloc()

["Jan Beulich" <JBeulich@xxxxxxxx>]

Ping? (This is expected to fix recurring testsuite failures.)

>>> On 18.07.13 at 11:59, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> Also add another pair of assertions to catch eventual further cases of
> incorrect accounting, and remove the temporary debuggin messages again
> which commit 68caac7f ("x86: don't use destroy_xen_mappings() for
> vunmap()") added.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/xen/common/vmap.c
> +++ b/xen/common/vmap.c
> @@ -57,8 +57,8 @@ void *vm_alloc(unsigned int nr, unsigned
>      {
>          struct page_info *pg;
>  
> -        ASSERT(!test_bit(vm_low, vm_bitmap));
> -        for ( start = vm_low; ; )
> +        ASSERT(vm_low == vm_top || !test_bit(vm_low, vm_bitmap));
> +        for ( start = vm_low; start < vm_top; )
>          {
>              bit = find_next_bit(vm_bitmap, vm_top, start + 1);
>              if ( bit > vm_top )
> @@ -68,12 +68,18 @@ void *vm_alloc(unsigned int nr, unsigned
>               * corresponding page a guard one.
>               */
>              start = (start + align) & ~(align - 1);
> -            if ( start + nr <= bit )
> -                break;
> -            start = bit < vm_top ?
> -                    find_next_zero_bit(vm_bitmap, vm_top, bit + 1) : bit;
> -            if ( start >= vm_top )
> -                break;
> +            if ( bit < vm_top )
> +            {
> +                if ( start + nr < bit )
> +                    break;
> +                start = find_next_zero_bit(vm_bitmap, vm_top, bit + 1);
> +            }
> +            else
> +            {
> +                if ( start + nr <= bit )
> +                    break;
> +                start = bit;
> +            }
>          }
>  
>          if ( start < vm_top )
> @@ -115,6 +121,10 @@ void *vm_alloc(unsigned int nr, unsigned
>  
>      for ( bit = start; bit < start + nr; ++bit )
>          __set_bit(bit, vm_bitmap);
> +    if ( bit < vm_top )
> +        ASSERT(!test_bit(bit, vm_bitmap));
> +    else
> +        ASSERT(bit == vm_top);
>      if ( start <= vm_low + 2 )
>          vm_low = bit;
>      spin_unlock(&vm_lock);
> @@ -177,7 +187,6 @@ void *__vmap(const unsigned long *mfn, u
>      void *va = vm_alloc(nr * granularity, align);
>      unsigned long cur = (unsigned long)va;
>  
> -printk("vmap(%p:%#x)\n", va, nr * granularity);//temp
>      for ( ; va && nr--; ++mfn, cur += PAGE_SIZE * granularity )
>      {
>          if ( map_pages_to_xen(cur, *mfn, granularity, flags) )
> @@ -202,7 +211,6 @@ void vunmap(const void *va)
>  
>      destroy_xen_mappings(addr, addr + PAGE_SIZE * vm_size(va));
>  #else /* Avoid tearing down intermediate page tables. */
> -printk("vunmap(%p:%#x)\n", va, vm_size(va));//temp
>      map_pages_to_xen((unsigned long)va, 0, vm_size(va), _PAGE_NONE);
>  #endif
>      vm_free(va);




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