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

LEROY Christophe
2024-08-14T16:50:23Z

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(-)
>