Re: Instability in current -git tree

[Pavel Tatashin <pasha.tatashin@oracle.com>]

> Maybe a stupid question, but I do not see it from the code (this init
> code is just to complex to keep it cached in head so I always have to
> study the code again and again, sigh). So what exactly prevents
> memmap_init_zone to stumble over reserved regions? We do play some ugly
> games to find a first !reserved pfn in the node but I do not really see
> anything in the init path to properly skip over reserved holes inside
> the node.

Hi Michal,

This is not a stupid question. I figured out how this whole thing
became broken:  Revert "mm: page_alloc: skip over regions of invalid
pfns where possible" caused that.

Because, before that was reverted, memmap_init_zone() would use
memblock.memory to check that only pages that have physical backing
are initialized. But, now after that was reverted zer_resv_unavail()
scheme became totally broken.

The concept is quite easy: zero all the allocated memmap memory that
has not been initialized by memmap_init_zone(). So, I think I will
modify memmap_init_zone() to zero the skipped pfns that have memmap
backing. But, that requires more thinking.

Thank you,
Pavel