Re: [Xen-devel] [PATCH 13/22] mini-os: correct wrong calculation of alloc bitmap size

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

Juergen Gross, on Tue 23 Aug 2016 17:15:59 +0200, wrote:
> When remapping the page allocator's bitmap for the ballooning support
> the calculation of the needed size is wrong. This doesn't really
> matter today as nothing is allocated after that bitmap, but it should
> be corrected nevertheless.

Oops, indeed!

> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

Reviewed-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>

> ---
>  balloon.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/balloon.c b/balloon.c
> index 8d2f151..8669edb 100644
> --- a/balloon.c
> +++ b/balloon.c
> @@ -52,7 +52,7 @@ void mm_alloc_bitmap_remap(void)
>  {
>      unsigned long i;
>  
> -    if ( mm_alloc_bitmap_size >= ((nr_max_pages + 1) >> (PAGE_SHIFT + 3)) )
> +    if ( mm_alloc_bitmap_size >= ((nr_max_pages + 1) >> 3) )
>          return;
>  
>      for ( i = 0; i < mm_alloc_bitmap_size; i += PAGE_SIZE )
> @@ -62,7 +62,7 @@ void mm_alloc_bitmap_remap(void)
>      }
>  
>      mm_alloc_bitmap = (unsigned long *)virt_kernel_area_end;
> -    virt_kernel_area_end += round_pgup((nr_max_pages + 1) >> (PAGE_SHIFT + 
> 3));
> +    virt_kernel_area_end += round_pgup((nr_max_pages + 1) >> 3);
>      ASSERT(virt_kernel_area_end <= VIRT_DEMAND_AREA);
>  }
>  
> -- 
> 2.6.6
> 

-- 
Samuel
/*
 * [...] Note that 120 sec is defined in the protocol as the maximum
 * possible RTT.  I guess we'll have to use something other than TCP
 * to talk to the University of Mars.
 * PAWS allows us longer timeouts and large windows, so once implemented
 * ftp to mars will work nicely.
 */
(from /usr/src/linux/net/inet/tcp.c, concerning RTT [retransmission timeout])

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