Messages in this thread | | | Date | Tue, 27 Feb 2024 10:53:17 +0100 | Subject | Re: [PATCH] mm: export folio_pte_batch as a couple of modules might need it | From | David Hildenbrand <> |
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On 27.02.24 10:51, Lance Yang wrote: > On Tue, Feb 27, 2024 at 5:14 PM David Hildenbrand <david@redhat.com> wrote: >> >> On 27.02.24 10:07, Ryan Roberts wrote: >>> On 27/02/2024 02:40, Barry Song wrote: >>>> From: Barry Song <v-songbaohua@oppo.com> >>>> >>>> madvise and some others might need folio_pte_batch to check if a range >>>> of PTEs are completely mapped to a large folio with contiguous physcial >>>> addresses. Let's export it for others to use. >>>> >>>> Cc: Lance Yang <ioworker0@gmail.com> >>>> Cc: Ryan Roberts <ryan.roberts@arm.com> >>>> Cc: David Hildenbrand <david@redhat.com> >>>> Cc: Yin Fengwei <fengwei.yin@intel.com> >>>> Signed-off-by: Barry Song <v-songbaohua@oppo.com> >>>> --- >>>> -v1: >>>> at least two jobs madv_free and madv_pageout depend on it. To avoid >>>> conflicts and dependencies, after discussing with Lance, we prefer >>>> this one can land earlier. >>> >>> I think this will also ultimately be useful for mprotect too, though I haven't >>> looked at it properly yet. >>> >> >> Yes, I think we briefly discussed that. >> >>>> >>>> mm/internal.h | 13 +++++++++++++ >>>> mm/memory.c | 11 +---------- >>>> 2 files changed, 14 insertions(+), 10 deletions(-) >>>> >>>> diff --git a/mm/internal.h b/mm/internal.h >>>> index 13b59d384845..8e2bc304f671 100644 >>>> --- a/mm/internal.h >>>> +++ b/mm/internal.h >>>> @@ -83,6 +83,19 @@ static inline void *folio_raw_mapping(struct folio *folio) >>>> return (void *)(mapping & ~PAGE_MAPPING_FLAGS); >>>> } >>>> >>>> +/* Flags for folio_pte_batch(). */ >>>> +typedef int __bitwise fpb_t; >>>> + >>>> +/* Compare PTEs after pte_mkclean(), ignoring the dirty bit. */ >>>> +#define FPB_IGNORE_DIRTY ((__force fpb_t)BIT(0)) >>>> + >>>> +/* Compare PTEs after pte_clear_soft_dirty(), ignoring the soft-dirty bit. */ >>>> +#define FPB_IGNORE_SOFT_DIRTY ((__force fpb_t)BIT(1)) >>>> + >>>> +extern int folio_pte_batch(struct folio *folio, unsigned long addr, >>>> + pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags, >>>> + bool *any_writable); >>>> + >>>> void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio, >>>> int nr_throttled); >>>> static inline void acct_reclaim_writeback(struct folio *folio) >>>> diff --git a/mm/memory.c b/mm/memory.c >>>> index 1c45b6a42a1b..319b3be05e75 100644 >>>> --- a/mm/memory.c >>>> +++ b/mm/memory.c >>>> @@ -953,15 +953,6 @@ static __always_inline void __copy_present_ptes(struct vm_area_struct *dst_vma, >>>> set_ptes(dst_vma->vm_mm, addr, dst_pte, pte, nr); >>>> } >>>> >>>> -/* Flags for folio_pte_batch(). */ >>>> -typedef int __bitwise fpb_t; >>>> - >>>> -/* Compare PTEs after pte_mkclean(), ignoring the dirty bit. */ >>>> -#define FPB_IGNORE_DIRTY ((__force fpb_t)BIT(0)) >>>> - >>>> -/* Compare PTEs after pte_clear_soft_dirty(), ignoring the soft-dirty bit. */ >>>> -#define FPB_IGNORE_SOFT_DIRTY ((__force fpb_t)BIT(1)) >>>> - >>>> static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) >>>> { >>>> if (flags & FPB_IGNORE_DIRTY) >>>> @@ -982,7 +973,7 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) >>>> * If "any_writable" is set, it will indicate if any other PTE besides the >>>> * first (given) PTE is writable. >>>> */ >>> >>> David was talking in Lance's patch thread, about improving the docs for this >>> function now that its exported. Might be worth syncing on that. >> >> Here is my take: >> >> Signed-off-by: David Hildenbrand <david@redhat.com> >> --- >> mm/memory.c | 22 ++++++++++++++++++---- >> 1 file changed, 18 insertions(+), 4 deletions(-) >> >> diff --git a/mm/memory.c b/mm/memory.c >> index d0b855a1837a8..098356b8805ae 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -971,16 +971,28 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags) >> return pte_wrprotect(pte_mkold(pte)); >> } >> >> -/* >> +/** >> + * folio_pte_batch - detect a PTE batch for a large folio >> + * @folio: The large folio to detect a PTE batch for. >> + * @addr: The user virtual address the first page is mapped at. >> + * @start_ptep: Page table pointer for the first entry. >> + * @pte: Page table entry for the first page. >> + * @max_nr: The maximum number of table entries to consider. >> + * @flags: Flags to modify the PTE batch semantics. >> + * @any_writable: Optional pointer to indicate whether any entry except the >> + * first one is writable. >> + * >> * Detect a PTE batch: consecutive (present) PTEs that map consecutive >> - * pages of the same folio. >> + * pages of the same large folio. >> * >> * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN, >> * the accessed bit, writable bit, dirty bit (with FPB_IGNORE_DIRTY) and >> * soft-dirty bit (with FPB_IGNORE_SOFT_DIRTY). >> * >> - * If "any_writable" is set, it will indicate if any other PTE besides the >> - * first (given) PTE is writable. >> + * start_ptep must map any page of the folio. max_nr must be at least one and >> + * must be limited by the caller so scanning cannot exceed a single page table. >> + * >> + * Return: the number of table entries in the batch. >> */ >> static inline int folio_pte_batch(struct folio *folio, unsigned long addr, >> pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags, >> @@ -996,6 +1008,8 @@ static inline int folio_pte_batch(struct folio *folio, unsigned long addr, >> *any_writable = false; >> >> VM_WARN_ON_FOLIO(!pte_present(pte), folio); >> + VM_WARN_ON_FOLIO(!folio_test_large(folio) || max_nr < 1, folio); >> + VM_WARN_ON_FOLIO(page_folio(pfn_to_page(pte_pfn(pte))) != folio, folio); > > Nit: > IIUC, the pte that maps to the first page. > - VM_WARN_ON_FOLIO(page_folio(pfn_to_page(pte_pfn(pte))) != > folio, folio); > + VM_WARN_ON_FOLIO(pte_pfn(pte) != folio_pfn(folio), folio);
That would only work if the PTE would map the very first subpage of the folio, not any subpage?
-- Cheers,
David / dhildenb
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