4.18-stable review patch. If anyone has any objections, please let me know.
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From: James Morse james.morse@arm.com
commit f52bb98f5aded4c43e52f5ce19fb83f7261e9e73 upstream.
Commit 6d526ee26ccd ("arm64: mm: enable CONFIG_HOLES_IN_ZONE for NUMA") only enabled HOLES_IN_ZONE for NUMA systems because the NUMA code was choking on the missing zone for nomap pages. This problem doesn't just apply to NUMA systems.
If the architecture doesn't set HAVE_ARCH_PFN_VALID, pfn_valid() will return true if the pfn is part of a valid sparsemem section.
When working with multiple pages, the mm code uses pfn_valid_within() to test each page it uses within the sparsemem section is valid. On most systems memory comes in MAX_ORDER_NR_PAGES chunks which all have valid/initialised struct pages. In this case pfn_valid_within() is optimised out.
Systems where this isn't true (e.g. due to nomap) should set HOLES_IN_ZONE and provide HAVE_ARCH_PFN_VALID so that mm tests each page as it works with it.
Currently non-NUMA arm64 systems can't enable HOLES_IN_ZONE, leading to a VM_BUG_ON():
| page:fffffdff802e1780 is uninitialized and poisoned | raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff | raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff | page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) | ------------[ cut here ]------------ | kernel BUG at include/linux/mm.h:978! | Internal error: Oops - BUG: 0 [#1] PREEMPT SMP [...] | CPU: 1 PID: 25236 Comm: dd Not tainted 4.18.0 #7 | Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 | pstate: 40000085 (nZcv daIf -PAN -UAO) | pc : move_freepages_block+0x144/0x248 | lr : move_freepages_block+0x144/0x248 | sp : fffffe0071177680 [...] | Process dd (pid: 25236, stack limit = 0x0000000094cc07fb) | Call trace: | move_freepages_block+0x144/0x248 | steal_suitable_fallback+0x100/0x16c | get_page_from_freelist+0x440/0xb20 | __alloc_pages_nodemask+0xe8/0x838 | new_slab+0xd4/0x418 | ___slab_alloc.constprop.27+0x380/0x4a8 | __slab_alloc.isra.21.constprop.26+0x24/0x34 | kmem_cache_alloc+0xa8/0x180 | alloc_buffer_head+0x1c/0x90 | alloc_page_buffers+0x68/0xb0 | create_empty_buffers+0x20/0x1ec | create_page_buffers+0xb0/0xf0 | __block_write_begin_int+0xc4/0x564 | __block_write_begin+0x10/0x18 | block_write_begin+0x48/0xd0 | blkdev_write_begin+0x28/0x30 | generic_perform_write+0x98/0x16c | __generic_file_write_iter+0x138/0x168 | blkdev_write_iter+0x80/0xf0 | __vfs_write+0xe4/0x10c | vfs_write+0xb4/0x168 | ksys_write+0x44/0x88 | sys_write+0xc/0x14 | el0_svc_naked+0x30/0x34 | Code: aa1303e0 90001a01 91296421 94008902 (d4210000) | ---[ end trace 1601ba47f6e883fe ]---
Remove the NUMA dependency.
Link: https://www.spinics.net/lists/arm-kernel/msg671851.html Cc: stable@vger.kernel.org Cc: Ard Biesheuvel ard.biesheuvel@linaro.org Reported-by: Mikulas Patocka mpatocka@redhat.com Reviewed-by: Pavel Tatashin pavel.tatashin@microsoft.com Tested-by: Mikulas Patocka mpatocka@redhat.com Signed-off-by: James Morse james.morse@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/Kconfig | 1 - 1 file changed, 1 deletion(-)
--- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -754,7 +754,6 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
config HOLES_IN_ZONE def_bool y - depends on NUMA
source kernel/Kconfig.preempt source kernel/Kconfig.hz