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Tue, 27 Feb 2024 01:57:12 -0800 (PST) MIME-Version: 1.0 References: <20240227024050.244567-1-21cnbao@gmail.com> <61b9dfc9-5522-44fd-89a4-140833ede8af@arm.com> In-Reply-To: From: Lance Yang Date: Tue, 27 Feb 2024 17:57:00 +0800 Message-ID: Subject: Re: [PATCH] mm: export folio_pte_batch as a couple of modules might need it To: David Hildenbrand Cc: Ryan Roberts , Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Barry Song , Yin Fengwei Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 47FAE1C0019 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: g67yykenrr3jse9wsw6kjpz5h6atu4cr X-HE-Tag: 1709027833-565947 X-HE-Meta: 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 ykktjuBn JqlUfHLScGQMAq7ZvkzC9rsaYo8mrflDvGo8fMjhXGXnSnCD8nBKdKYSxhJ2XW4TOpF9d3snEPCOdGv92Q4jv6qddyIseQ+ijIJwVrnDTiAFGVIbGNDigSnadbs2itVQGhQSql+vQs89tW+b7xkifpmebhn8LBblfKNNv1cJbo61jHe50iVgkeWEg/FL3bAlvIu/x93WJw7SPyxrL+/tuUtC9KE+jZfz++pQdQnsSeBrg0OvJyAFMxt+g777kQjKVz9V1srEHaZJ+jwY5OZYNT420qEm2hsfWa6dumHOpuEAvOAByPARUdJwx1jn2Pgpnny++wXLgDuQ/zKkpsVDw51iiLmm10NaJux99voJynMcGndwyU9wcWn2dVLLwKNSaHaEPiFAcuv/AbOoz5qyDudex5+zAcmJebjIDMMNCiIYMvyzhltF8H1XZF9Be2UvsT0eHE8lPMH3SNLemnlWydXrwbxPYjjgm0zbYzyQKeUUec8I2HS+f4bKrGPwBkVt1l5ubaosuUVNsK+XkvCS4ZMHN4+BrFZjhBjjigFAvAsFqfdEzjcO1RwE292zLMdwBqJPZBMVW+oOoABBytb2BEQvLS/uYeVBmRbUni5psivQHn2c= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Feb 27, 2024 at 5:53=E2=80=AFPM David Hildenbrand wrote: > > On 27.02.24 10:51, Lance Yang wrote: > > On Tue, Feb 27, 2024 at 5:14=E2=80=AFPM David Hildenbrand wrote: > >> > >> On 27.02.24 10:07, Ryan Roberts wrote: > >>> On 27/02/2024 02:40, Barry Song wrote: > >>>> From: Barry Song > >>>> > >>>> madvise and some others might need folio_pte_batch to check if a ran= ge > >>>> of PTEs are completely mapped to a large folio with contiguous physc= ial > >>>> addresses. Let's export it for others to use. > >>>> > >>>> Cc: Lance Yang > >>>> Cc: Ryan Roberts > >>>> Cc: David Hildenbrand > >>>> Cc: Yin Fengwei > >>>> Signed-off-by: Barry Song > >>>> --- > >>>> -v1: > >>>> at least two jobs madv_free and madv_pageout depend on it. To avo= id > >>>> conflicts and dependencies, after discussing with Lance, we prefe= r > >>>> 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 foli= o *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-dir= ty 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 *fol= io, > >>>> 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-dir= ty bit. */ > >>>> -#define FPB_IGNORE_SOFT_DIRTY ((__force fpb_t)BIT(1)) > >>>> - > >>>> static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t fl= ags) > >>>> { > >>>> if (flags & FPB_IGNORE_DIRTY) > >>>> @@ -982,7 +973,7 @@ static inline pte_t __pte_batch_clear_ignored(pt= e_t pte, fpb_t flags) > >>>> * If "any_writable" is set, it will indicate if any other PTE be= sides the > >>>> * first (given) PTE is writable. > >>>> */ > >>> > >>> David was talking in Lance's patch thread, about improving the docs f= or this > >>> function now that its exported. Might be worth syncing on that. > >> > >> Here is my take: > >> > >> Signed-off-by: David Hildenbrand > >> --- > >> 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(pt= e_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 exce= pt the > >> + * first one is writable. > >> + * > >> * Detect a PTE batch: consecutive (present) PTEs that map consecut= ive > >> - * pages of the same folio. > >> + * pages of the same large folio. > >> * > >> * All PTEs inside a PTE batch have the same PTE bits set, excludin= g 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 beside= s 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 p= age table. > >> + * > >> + * Return: the number of table entries in the batch. > >> */ > >> static inline int folio_pte_batch(struct folio *folio, unsigned lon= g 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 *f= olio, unsigned long addr, > >> *any_writable =3D 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))) !=3D fo= lio, folio); > > > > Nit: > > IIUC, the pte that maps to the first page. > > - VM_WARN_ON_FOLIO(page_folio(pfn_to_page(pte_pfn(pte))) !=3D > > folio, folio); > > + VM_WARN_ON_FOLIO(pte_pfn(pte) !=3D folio_pfn(folio), folio); > > That would only work if the PTE would map the very first subpage of the > folio, not any subpage? You're right. I got it. > > -- > Cheers, > > David / dhildenb >