Reading a sysfs "memoryN/valid_zones" file leads to the following oops
when the first page of a range is not backed by struct page.
show_valid_zones() assumes that 'start_pfn' is always valid for
page_zone().
BUG: unable to handle kernel paging request at ffffea017a000000
IP: show_valid_zones+0x6f/0x160
This issue may happen on x86-64 systems with 64GiB or more memory since
their memory block size is bumped up to 2GiB. [1] An example of such
systems is desribed below. 0x3240000000 is only aligned by 1GiB and
this memory block starts from 0x3200000000, which is not backed by
struct page.
BIOS-e820: [mem 0x0000003240000000-0x000000603fffffff] usable
Since test_pages_in_a_zone() already checks holes, fix this issue by
extending this function to return 'valid_start' and 'valid_end' for a
given range. show_valid_zones() then proceeds with the valid range.
[1] 'Commit bdee237c03 ("x86: mm: Use 2GB memory block size on
large-memory x86-64 systems")'
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Toshi Kani <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Zhang Zhen <[email protected]>
Cc: Reza Arbab <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: <[email protected]> [4.4+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Toshi Kani
a96dfddbcc