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.I thought you were runnning with the debugging which poisons all the allocated memory...
Yes, but as I said, unfortunately memset(1) with CONFIG_VM_DEBUG does not catch this case. So, when CONFIG_VM_DEBUG is enabled kexec reboots without issues.
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().Yes, that would make much more sense to me.
Ok, so should I submit a new patch with two loops? (The logic within loops is going to be the same:
if (!pfn_valid_within(pfn)) {
} else if (!(pfn & nr_pgmask) && !pfn_valid(pfn)) {
} else if (!meminit_pfn_in_nid(pfn, nid, &nid_init_state)) {
} else if (page && (pfn & nr_pgmask)) {
This fix was already added into mm-tree as
mm-deferred_init_memmap-improvements-fix-2.patch
Thank you,
Pasha
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