A sysfs memory file is created for each 2GiB memory block on x86-64
when the system has 64GiB or more memory. [1] When the start address
of a memory block is not backed by struct page, i.e. a memory range is
not aligned by 2GiB, reading its 'valid_zones' attribute file leads to
a kernel oops. This issue was observed on multiple x86-64 systems
with more than 64GiB of memory. This patch-set fixes this issue.
Patch 1 first fixes an issue in test_pages_in_a_zone(), which does
not test the start section.
Patch 2 then fixes the kernel oops by extending test_pages_in_a_zone()
to return valid [start, end).
Note for stable kernels: The memory block size change was made by commit
bdee237c034, which was accepted to 3.9. However, this patch-set depends
on (and fixes) the change to test_pages_in_a_zone() made by commit
5f0f2887f4, which was accepted to 4.4. So, I recommend that we backport
it up to 4.4.
[1] 'Commit bdee237c0343 ("x86: mm: Use 2GB memory block size on
large-memory x86-64 systems")'
v2:
- Rebase to the -mm tree. (Andrew Morton)
- Add more descriptions about the issue. (Andrew Morton)
- Add cc to stable kernels. (Greg Kroah-Hartman, Andrew Morton)
---
Toshi Kani (2):
1/2 mm/memory_hotplug.c: check start_pfn in test_pages_in_a_zone()
2/2 base/memory, hotplug: fix a kernel oops in show_valid_zones()
---
drivers/base/memory.c | 12 ++++++------
include/linux/memory_hotplug.h | 3 ++-
mm/memory_hotplug.c | 28 +++++++++++++++++++++-------
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