On 11/02/2017 09:54 AM, Michal Hocko wrote:
On Thu 02-11-17 09:39:58, Pavel Tatashin wrote:
[...]
Hi Michal,
Previously as before my project? That is because memory for all struct pages
was always zeroed in memblock, and in __free_one_page() page_is_buddy() was
always returning false, thus we never tried to incorrectly remove it from
the list:
837 list_del(&buddy->lru);
Now, that memory is not zeroed, page_is_buddy() can return true after kexec
when memory is dirty (unfortunately memset(1) with CONFIG_VM_DEBUG does not
catch this case). And proceed further to incorrectly remove buddy from the
list.
OK, I thought this was a regression from one of the recent patches. So
the problem is not new. Why don't we see the same problem during the
standard boot?
Because, I believe, BIOS is zeroing all the memory for us.
This is why we must initialize the computed buddy page beforehand.
Ble, this is really ugly. I will think about it more.
Another approach that I considered is to split loop inside
deferred_init_range() into two loops: one where we initialize pages by
calling __init_single_page(), another where we free them to buddy
allocator by calling deferred_free_range().
Pasha
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