Subject: Re: [PATCH v2 0/2] mm: unify the allocation of pglist_data instances

From: Mike Rapoport <[email-masked]>
Date: Tue, 18 May 2021 19:09:40 +0300

Hello Miles,

On Tue, May 18, 2021 at 05:24:44PM +0800, Miles Chen wrote:
> This patches is created to fix the __pa() warning messages when
> CONFIG_DEBUG_VIRTUAL=y by unifying the allocation of pglist_data
> instances.
> 
> In current implementation of node_data, if CONFIG_NEED_MULTIPLE_NODES=y,
> pglist_data is allocated by a memblock API. If CONFIG_NEED_MULTIPLE_NODES=n,
> we use a global variable named "contig_page_data".
> 
> If CONFIG_DEBUG_VIRTUAL is not enabled. __pa() can handle both
> allocation and symbol cases. But if CONFIG_DEBUG_VIRTUAL is set,
> we will have the "virt_to_phys used for non-linear address" warning
> when booting.
> 
> To fix the warning, always allocate pglist_data by memblock APIs and
> remove the usage of contig_page_data.

Somehow I was sure that we can allocate pglist_data before it is accessed
in sparse_init() somewhere outside mm/sparse.c. It's really not the case
and having two places that may allocated this structure is surely worth
than your previous suggestion.

Sorry about that.
 
> Warning message:
> [    0.000000] ------------[ cut here ]------------
> [    0.000000] virt_to_phys used for non-linear address: (____ptrval____) (contig_page_data+0x0/0x1c00)
> [    0.000000] WARNING: CPU: 0 PID: 0 at arch/arm64/mm/physaddr.c:15 __virt_to_phys+0x58/0x68
> [    0.000000] Modules linked in:
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Tainted: G        W         5.13.0-rc1-00074-g1140ab592e2e #3
> [    0.000000] Hardware name: linux,dummy-virt (DT)
> [    0.000000] pstate: 600000c5 (nZCv daIF -PAN -UAO -TCO BTYPE=--)
> [    0.000000] pc : __virt_to_phys+0x58/0x68
> [    0.000000] lr : __virt_to_phys+0x54/0x68
> [    0.000000] sp : ffff800011833e70
> [    0.000000] x29: ffff800011833e70 x28: 00000000418a0018 x27: 0000000000000000
> [    0.000000] x26: 000000000000000a x25: ffff800011b70000 x24: ffff800011b70000
> [    0.000000] x23: fffffc0001c00000 x22: ffff800011b70000 x21: 0000000047ffffb0
> [    0.000000] x20: 0000000000000008 x19: ffff800011b082c0 x18: ffffffffffffffff
> [    0.000000] x17: 0000000000000000 x16: ffff800011833bf9 x15: 0000000000000004
> [    0.000000] x14: 0000000000000fff x13: ffff80001186a548 x12: 0000000000000000
> [    0.000000] x11: 0000000000000000 x10: 00000000ffffffff x9 : 0000000000000000
> [    0.000000] x8 : ffff8000115c9000 x7 : 737520737968705f x6 : ffff800011b62ef8
> [    0.000000] x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
> [    0.000000] x2 : 0000000000000000 x1 : ffff80001159585e x0 : 0000000000000058
> [    0.000000] Call trace:
> [    0.000000]  __virt_to_phys+0x58/0x68
> [    0.000000]  check_usemap_section_nr+0x50/0xfc
> [    0.000000]  sparse_init_nid+0x1ac/0x28c
> [    0.000000]  sparse_init+0x1c4/0x1e0
> [    0.000000]  bootmem_init+0x60/0x90
> [    0.000000]  setup_arch+0x184/0x1f0
> [    0.000000]  start_kernel+0x78/0x488
> [    0.000000] ---[ end trace f68728a0d3053b60 ]---
> 
> [1] https://lore.kernel.org/patchwork/patch/1425110/
> 
> Change since v1:
> - use memblock_alloc() to create pglist_data when CONFIG_NUMA=n
> 
> Miles Chen (2):
>   mm: introduce prepare_node_data
>   mm: replace contig_page_data with node_data
> 
>  Documentation/admin-guide/kdump/vmcoreinfo.rst | 13 -------------
>  arch/powerpc/kexec/core.c                      |  5 -----
>  include/linux/gfp.h                            |  3 ---
>  include/linux/mm.h                             |  2 ++
>  include/linux/mmzone.h                         |  4 ++--
>  kernel/crash_core.c                            |  1 -
>  mm/memblock.c                                  |  3 +--
>  mm/page_alloc.c                                | 16 ++++++++++++++++
>  mm/sparse.c                                    |  2 ++
>  9 files changed, 23 insertions(+), 26 deletions(-)
> 
> 
> base-commit: 8ac91e6c6033ebc12c5c1e4aa171b81a662bd70f
> -- 
> 2.18.0
> 

-- 
Sincerely yours,
Mike.

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