From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 723CB135A6E for ; Tue, 27 Feb 2024 09:20:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709025623; cv=none; b=vDGkrYT4LPmUn0aOCynxCTQhxhGAOEhONXMLMJch43FNyWzkCZSbcIbdbMuhRHWeX5Eg89nYYjJ7Eywis0dv6GLZMxJwXNcGzj6fXMvfUm67aITQZEj0JPtSTh/h4UXqJC7OnCDAuPWgRutwSfpSfG1N9BwJoRSTSOx4Y7bIprY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709025623; c=relaxed/simple; bh=oB9w23lzQaXPWqAv3hlyO3XSewGD1nXDKFxZM6b+2cc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=oQhDXoBhciLGUt3+unZZFmcz3IopHAYs2tpEykYqUWv2AZzuncV/0FhPevd/I1Y16632/gh4YsupEg6/a8xx66wYv0U9YER18Y5M+6v6C6mkAgzsTJSvZXXoB9cG6MHhE31/HP02VXTKCehDP0bIvdD5fcJpuUR06mlGK7d58Os= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 39A40DA7; Tue, 27 Feb 2024 01:20:59 -0800 (PST) Received: from [10.57.67.4] (unknown [10.57.67.4]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A75833F762; Tue, 27 Feb 2024 01:20:18 -0800 (PST) Message-ID: <74958d41-6d73-4f5a-aae7-33dc374b6ddb@arm.com> Date: Tue, 27 Feb 2024 09:20:16 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: export folio_pte_batch as a couple of modules might need it Content-Language: en-GB To: David Hildenbrand , Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Barry Song , Lance Yang , Yin Fengwei References: <20240227024050.244567-1-21cnbao@gmail.com> <61b9dfc9-5522-44fd-89a4-140833ede8af@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 27/02/2024 09:14, 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 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 >>> 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 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 > --- >  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. >   */ LGTM! >  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); >   >      nr = pte_batch_hint(start_ptep, pte); >      expected_pte = __pte_batch_clear_ignored(pte_advance_pfn(pte, nr), flags);