tree 18fdac93ceb6768bfb1a380e586a5e7342ce40b7
parent f17b5f06cb92ef2250513a1e154c47b78df07d40
author Michal Hocko <mhocko@suse.com> 1548439738 +0100
committer Linus Torvalds <torvalds@linux-foundation.org> 1548700522 -0800

Revert "mm, memory_hotplug: initialize struct pages for the full memory section"

This reverts commit 2830bf6f05fb3e05bc4743274b806c821807a684.

The underlying assumption that one sparse section belongs into a single
numa node doesn't hold really. Robert Shteynfeld has reported a boot
failure. The boot log was not captured but his memory layout is as
follows:

  Early memory node ranges
    node   1: [mem 0x0000000000001000-0x0000000000090fff]
    node   1: [mem 0x0000000000100000-0x00000000dbdf8fff]
    node   1: [mem 0x0000000100000000-0x0000001423ffffff]
    node   0: [mem 0x0000001424000000-0x0000002023ffffff]

This means that node0 starts in the middle of a memory section which is
also in node1.  memmap_init_zone tries to initialize padding of a
section even when it is outside of the given pfn range because there are
code paths (e.g.  memory hotplug) which assume that the full worth of
memory section is always initialized.

In this particular case, though, such a range is already intialized and
most likely already managed by the page allocator.  Scribbling over
those pages corrupts the internal state and likely blows up when any of
those pages gets used.

Reported-by: Robert Shteynfeld <robert.shteynfeld@gmail.com>
Fixes: 2830bf6f05fb ("mm, memory_hotplug: initialize struct pages for the full memory section")
Cc: stable@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>