[Crash-utility] [PATCH] display information about "struct page" on SPARSEMEM.

[Dave Anderson]

Ken'ichi Ohmichi wrote:
> Hi Dave,
> 
> This patch fixes the problem that the crash utility cannot display
> "struct page" information about SPARSEMEM (not SPARSEMEM_EXTREME) properly.
> 
> The symbol mem_section is defined as the pointer array in SPARSEMEM_EXTREME.
> On the other hand, SPARSEMEM's one is defined as the array of structure
> mem_section like the following:
> 
> linux-2.6.23/mm/sparse.c:18L
>   #ifdef CONFIG_SPARSEMEM_EXTREME
>   struct mem_section *mem_section[NR_SECTION_ROOTS]
>           ____cacheline_internodealigned_in_smp;
>   #else
>   struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT]
>            ____cacheline_internodealigned_in_smp;
>   #endif
>   EXPORT_SYMBOL(mem_section);
> 
> The crash utility considers SPARSEMEM's one to be the pointer array,
> but it is wrong. This patch fixes it.
> 

Interesting, I've never seen this problem before on any
SPARSEMEM kernels.  But perhaps the original contributor
of this patch, and myself, have never run a kernel configured
with CONFIG_SPARSEMEM (i.e., only with CONFIG_SPARSEMEM_EXTREME)?
(I don't have any dumpfiles to check)

In any case, can you confirm that this patch work for both cases?
In other words, there is a differentiation between the _EXTREME and
the non-EXTREME cases in the crash utility.  Should the patch be an
if-else situation?

Dave



> The following results are this patch effects.
> 
> * Before applying this patch
>  crash> kmem -p
>    PAGE    PHYSICAL   MAPPING    INDEX CNT FLAGS
>  100              0   -------    -----   0 0
>  120           1000   -------    -----   0 0
>  140           2000   -------    -----   0 0
>  160           3000   -------    -----   0 0
>  180           4000   -------    -----   0 0
>  1a0           5000   -------    -----   0 0
>  1c0           6000   -------    -----   0 0
>  1e0           7000   -------    -----   0 0
>  200           8000   -------    -----   0 0
>  [snip]
>  crash>
> 
> * After applying this patch
>  crash> kmem -p
>    PAGE    PHYSICAL   MAPPING    INDEX CNT FLAGS
>  c5000000         0   -------    -----   1 400
>  c5000020      1000   -------    -----   1 400
>  c5000040      2000   -------    -----   1 400
>  c5000060      3000   -------    -----   1 400
>  c5000080      4000   -------    -----   1 400
>  c50000a0      5000   -------    -----   1 400
>  c50000c0      6000   -------    -----   1 400
>  c50000e0      7000   -------    -----   1 400
>  c5000100      8000   -------    -----   0 80000
>  [snip]
>  crash>
> 
> 
> Thanks
> Ken'ichi Ohmichi
> 
> ---
> Signed-off-by: Ken'ichi Ohmichi <oomichi at mxs.nes.nec.co.jp>
> 
> ---
> diff -rpuN crash-4.0-4.8.org/memory.c crash-4.0-4.8/memory.c
> --- crash-4.0-4.8.org/memory.c	2007-10-31 11:49:16.000000000 +0900
> +++ crash-4.0-4.8/memory.c	2007-11-01 10:28:15.000000000 +0900
> @@ -12229,7 +12229,9 @@ nr_to_section(ulong nr)
>  		addr = mem_sec[SECTION_NR_TO_ROOT(nr)] + 
>  		    (nr & SECTION_ROOT_MASK()) * SIZE(mem_section);
>  	else
> -		addr = mem_sec[0] + (nr & SECTION_ROOT_MASK()) * SIZE(mem_section);
> +		addr = symbol_value("mem_section") +
> +		    (SECTIONS_PER_ROOT() * SECTION_NR_TO_ROOT(nr) +
> +			(nr & SECTION_ROOT_MASK())) * SIZE(mem_section);
>  
>  	if (!IS_KVADDR(addr))
>  		return 0;
> _
> 
> 
> 
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