lkml.org 
[lkml]   [2020]   [Feb]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] mm/sparsemem: get physical address to page struct instead of virtual address to pfn
On Thu, Feb 06, 2020 at 06:19:46PM -0800, Dan Williams wrote:
>On Thu, Feb 6, 2020 at 3:17 PM Wei Yang <richardw.yang@linux.intel.com> wrote:
>>
>> memmap should be the physical address to page struct instead of virtual
>> address to pfn.
>>
>> Since we call this only for SPARSEMEM_VMEMMAP, pfn_to_page() is valid at
>> this point.
>>
>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>> CC: Dan Williams <dan.j.williams@intel.com>
>> ---
>> mm/sparse.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index b5da121bdd6e..56816f653588 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -888,7 +888,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>> /* Align memmap to section boundary in the subsection case */
>> if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) &&
>> section_nr_to_pfn(section_nr) != start_pfn)
>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
>> + memmap = pfn_to_page(section_nr_to_pfn(section_nr));
>
>Yes, this looks obviously correct. This might be tripping up
>makedumpfile. Do you see any practical effects of this bug? The kernel
>mostly avoids ->section_mem_map in the vmemmap case and in the
>!vmemmap case section_nr_to_pfn(section_nr) should always equal
>start_pfn.

I took another look into the code. Looks there is no practical effect after
this. Because in the vmemmap case, we don't need ->section_mem_map to retrieve
the real memmap.

But leave a inconsistent data in section_mem_map is not a good practice.

--
Wei Yang
Help you, Help me

\
 
 \ /
  Last update: 2020-02-07 12:27    [W:0.455 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site