On Fri, 2017-01-27 at 08:48 +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > On Thu, Jan 26, 2017 at 10:26:23PM +0000, Kani, Toshimitsu wrote: > > On Thu, 2017-01-26 at 13:52 -0800, Andrew Morton wrote: > > > On Thu, 26 Jan 2017 14:44:15 -0700 Toshi Kani <toshi.kani@xxxxxxx > > > > > > > wrote: > > > > > > > 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 > > > > > > > > Since test_pages_in_a_zone() already checks holes, extend this > > > > function to return 'valid_start' and 'valid_end' for a given > > > > range. show_valid_zones() then proceeds with the valid range. > > > > > > This doesn't apply to current mainline due to changes in > > > zone_can_shift(). Please redo and resend. > > > > Sorry, I will rebase to the -mm tree and resend the patches. > > > > > Please also update the changelog to provide sufficient > > > information for others to decide which kernel(s) need the > > > fix. In particular: under what circumstances will it occur? On > > > real machines which real people own? > > > > Yes, this issue happens on real x86 machines with 64GiB or more > > memory. On such systems, the memory block size is bumped up to > > 2GiB. [1] > > > > Here is an example system. 0x3240000000 is only aligned by 1GiB > > and its memory block starts from 0x3200000000, which is not backed > > by struct page. > > > > BIOS-e820: [mem 0x0000003240000000-0x000000603fffffff] usable > > > > I will add the descriptions to the patch. > > Should it also be backported to the stable kernels to resolve the > issue there? Yes, it should be backported to the 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, in the current form, I'd recommend we backport it up to 4.4. Thanks, -Toshi��.n������g��� �a��� �&ޖ)���)��h���&������梷���� �Ǟ�m������)������^�����������v���O��zf������
