Re: [RFC PATCH 00/18] use struct ptdesc to replace pgtable_t

[LEROY Christophe <christophe.leroy2@cs-soprasteria.com>]

Hi,

Le 30/07/2024 à 08:46, alexs@kernel.org a écrit :
> From: Alex Shi <alexs@kernel.org>
> 
> We have struct ptdesc for page table descriptor a year ago, but it
> has no much usages in kernel, while pgtable_t is used widely.
> 
> The pgtable_t is typedefed as 'pte_t *' in sparc, s390, powerpc and m68k
> except SUN3, others archs are all same as 'struct page *'.
> 
> These blocks the conception and code update for page table descriptor to
> struct ptdesc.
> 
> So, the simple idea to push the ptdesc conception forward is to update
> all pgtable_t by ptdesc or pte_t pointer. But this needs widely
> knowledges for most all of different archs. Common code change is easy
> for include/ and mm/ directory, but it's hard in all archs.
> 
> Thanks for intel LKP framework, I fixed most all of build issues except
> a bug on powerpc which reports a "struct ptdesc *" incompatible with
> struct ptdesc *' pointer issue...

Can you tell more about that problem on powerpc ? Which defconfig for 
instance ?

> 
> Another trouble is pmd_pgtable() conversion in the last patch.
> Maybe some of arch need define theirself own pmd_ptdesc()?
> 
> This patchset is immature, even except above 2 issues, I just tested
> virutal machine booting and kselftest mm on x86 and arm64.
> 
> Anyway any input are appreciated!

Can you tell on which tree you based this series ? Last patch doesn't 
apply on 6.11-rc1:

Applying: mm/pgtable: pass ptdesc in pte_free_defer
error: sha1 information is lacking or useless (mm/khugepaged.c).
error: could not build fake ancestor
Patch failed at 0019 mm/pgtable: pass ptdesc in pte_free_defer

Following hunk is the problem:

diff a/mm/khugepaged.c b/mm/khugepaged.c	(rejected hunks)
@@ -1777,7 +1777,7 @@ static void retract_page_tables(struct 
address_space *mapping, pgoff_t pgoff)
  		if (retracted) {
  			mm_dec_nr_ptes(mm);
  			page_table_check_pte_clear_range(mm, addr, pgt_pmd);
-			pte_free_defer(mm, pmd_pgtable(pgt_pmd));
+			pte_free_defer(mm, pmd_ptdesc(&pgt_pmd));
  		}
  	}
  	i_mmap_unlock_read(mapping);


Christophe

> 
> Thanks
> Alex
> 
> Alex Shi (18):
>    mm/pgtable: use ptdesc in pte_free_now/pte_free_defer
>    mm/pgtable: convert ptdesc.pmd_huge_pte to ptdesc pointer
>    fs/dax: use ptdesc in dax_pmd_load_hole
>    mm/thp: use ptdesc pointer in __do_huge_pmd_anonymous_page
>    mm/thp: use ptdesc in do_huge_pmd_anonymous_page
>    mm/thp: convert insert_pfn_pmd and its caller to use ptdesc
>    mm/thp: use ptdesc in copy_huge_pmd
>    mm/memory: use ptdesc in __pte_alloc
>    mm/pgtable: fully use ptdesc in pte_alloc_one series functions
>    mm/pgtable: pass ptdesc to pte_free()
>    mm/pgtable: introduce ptdesc_pfn and use ptdesc in free_pte_range()
>    mm/thp: pass ptdesc to set_huge_zero_folio function
>    mm/pgtable: return ptdesc pointer in pgtable_trans_huge_withdraw
>    mm/pgtable: use ptdesc in pgtable_trans_huge_deposit
>    mm/pgtable: pass ptdesc to pmd_populate
>    mm/pgtable: pass ptdesc to pmd_install
>    mm: convert vmf.prealloc_pte to struct ptdesc pointer
>    mm/pgtable: pass ptdesc in pte_free_defer
> 
>   arch/alpha/include/asm/pgalloc.h              |   4 +-
>   arch/arc/include/asm/pgalloc.h                |   4 +-
>   arch/arm/include/asm/pgalloc.h                |  13 +--
>   arch/arm/include/asm/tlb.h                    |   4 +-
>   arch/arm/mm/pgd.c                             |   2 +-
>   arch/arm64/include/asm/pgalloc.h              |   4 +-
>   arch/arm64/include/asm/tlb.h                  |   4 +-
>   arch/csky/include/asm/pgalloc.h               |   4 +-
>   arch/hexagon/include/asm/pgalloc.h            |   8 +-
>   arch/loongarch/include/asm/pgalloc.h          |   8 +-
>   arch/m68k/include/asm/motorola_pgalloc.h      |  12 +-
>   arch/m68k/include/asm/sun3_pgalloc.h          |   4 +-
>   arch/microblaze/include/asm/pgalloc.h         |   2 +-
>   arch/mips/include/asm/pgalloc.h               |   4 +-
>   arch/nios2/include/asm/pgalloc.h              |   4 +-
>   arch/openrisc/include/asm/pgalloc.h           |   8 +-
>   arch/parisc/include/asm/pgalloc.h             |   2 +-
>   arch/powerpc/include/asm/book3s/32/pgalloc.h  |   4 +-
>   arch/powerpc/include/asm/book3s/64/hash-4k.h  |   4 +-
>   arch/powerpc/include/asm/book3s/64/hash-64k.h |   4 +-
>   arch/powerpc/include/asm/book3s/64/pgalloc.h  |   4 +-
>   arch/powerpc/include/asm/book3s/64/pgtable.h  |   8 +-
>   arch/powerpc/include/asm/book3s/64/radix.h    |   4 +-
>   arch/powerpc/include/asm/pgalloc.h            |   8 +-
>   arch/powerpc/mm/book3s64/hash_pgtable.c       |  10 +-
>   arch/powerpc/mm/book3s64/radix_pgtable.c      |  10 +-
>   arch/riscv/include/asm/pgalloc.h              |   8 +-
>   arch/s390/include/asm/pgalloc.h               |   4 +-
>   arch/s390/include/asm/pgtable.h               |   4 +-
>   arch/s390/mm/pgalloc.c                        |   2 +-
>   arch/s390/mm/pgtable.c                        |  14 +--
>   arch/sh/include/asm/pgalloc.h                 |   4 +-
>   arch/sparc/include/asm/pgalloc_32.h           |   6 +-
>   arch/sparc/include/asm/pgalloc_64.h           |   2 +-
>   arch/sparc/include/asm/pgtable_64.h           |   4 +-
>   arch/sparc/mm/init_64.c                       |   2 +-
>   arch/sparc/mm/srmmu.c                         |   6 +-
>   arch/sparc/mm/tlb.c                           |  14 +--
>   arch/x86/include/asm/pgalloc.h                |  10 +-
>   arch/x86/mm/pgtable.c                         |   8 +-
>   arch/xtensa/include/asm/pgalloc.h             |  12 +-
>   fs/dax.c                                      |  14 +--
>   include/asm-generic/pgalloc.h                 |  10 +-
>   include/linux/mm.h                            |  16 ++-
>   include/linux/mm_types.h                      |   4 +-
>   include/linux/pgtable.h                       |   6 +-
>   mm/debug_vm_pgtable.c                         |   6 +-
>   mm/huge_memory.c                              | 103 +++++++++---------
>   mm/internal.h                                 |   2 +-
>   mm/khugepaged.c                               |  14 +--
>   mm/memory.c                                   |  15 +--
>   mm/mremap.c                                   |   2 +-
>   mm/pgtable-generic.c                          |  37 +++----
>   53 files changed, 240 insertions(+), 236 deletions(-)
>