Ken'ichi Ohmichi wrote:
> Hi Dave, Jay,
>
> Dave Anderson wrote:
>> We just ran into a similar problem using an older version of makedumpfile,
>> but looking at the latest makedumpfile code, it's seems that you could
>> run into the same problem.
>>
>> In exclude_unnecessary_pages(), if a physical page is in a memory
>> hole, then it skips the page and continues. In our case, that happened,
>> but when it started up again, the next legitimate pfn was well beyond
>> the previously-read cache of 512 pages. But since the new legit page
>> wasn't modulo-512, it didn't refresh the page cache, and it ended up
>> using stale page data (page->flags) and ended up excluding legitimate
>> pages:
>>
>> for (; pfn < mmd->pfn_end;
>> pfn++, mem_map += SIZE(page),
>> paddr += info->page_size) {
>>
>> /*
>> * Exclude the memory hole.
>> */
>> if (!is_in_segs(paddr))
>> continue;
>>
>> if ((pfn % PGMM_CACHED) == 0) {
>> if (pfn + PGMM_CACHED < mmd->pfn_end)
>> pfn_mm = PGMM_CACHED;
>> else
>> pfn_mm = mmd->pfn_end - pfn;
>> if (!readmem(VADDR, mem_map, page_cache,
>> SIZE(page) * pfn_mm))
>> goto out;
>> }
>>
>> We fixed it by doing something like this:
>>
>> if (!is_in_segs(paddr)) {
>> reset_cache = 1;
>> continue;
>> }
>>
>> if (((pfn % PGMM_CACHED) == 0) || reset_cache) {
>> reset_cache = 0;
>> ...
>
> Great, you are right.
> Thank you for fixing it :-)
>
> Jay, could you try Dave's fixing like the attached patch ?
Yes. I applied your version of Dave's patch and tried again.
It failed at a different pfn f600315:
a4700rac:/mnt/sda9/diskdump # rm dump.cd31; /var/tmp/jlan/makedumpfile
-cd31 -e 0xe0000f60031502f0 -x vmlinux.3 vmcore-cp.3 dump.cd31
Excluding unnecessary pages : [ 45 %]
pfn=f600315 flags=3c000000001026c
PAGE(vaddr:e0000f60031502f0, pfn:f600315) is excluded as CACHE PAGE.
Copying data : [100 %]
The dumpfile is saved to dump.cd31.
makedumpfile Completed.
Note the flags of pfn f600315. Crash checked on the pfn using the
vmcore-cp.3 and showed different flags:
crash> kmem -p f60031502f0
PAGE PHYSICAL MAPPING INDEX CNT FLAGS
a07ffffc45d00498 f6003150000 0 0 1 3c0000000000400
crash>
>
>
> Thanks
> Ken'ichi Ohmichi
>
