From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E719A5CDF1 for ; Sun, 23 Nov 2025 13:17:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763903865; cv=none; b=O8VR8J3xYMceJxLlGII/Qzdt46D8wicN07yA9+2FPoLgEUfOUfkWT5KHxEF6e/8yQODp7+8BYBaCDAdpu0pTV1Kx0+74whQQvCuj7xqSSSyAXo0NNHXto2DLP1mjwpjRDpBpQ8OGN49k5vAwOIvx1YKn/mVHygS9Pc8WkQxhU1U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763903865; c=relaxed/simple; bh=3UH0sUpcsTOMjRwBlMwUCGFDDjKFaDmhv/y2Ls/sfXU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lTUzjrO4UP1bS8MNdMMApcJyzRxO4s94KnGGtTsYe/xAF1abTQYw3QEkOcTJXjJW5wgG6kie5FRg7SoAb3E4UTo0cLOric7taRj4LI+gpHl5SiyQGQhSPNuAhRRpGUsmIBS1J/wy3Tpl9jJDoak64lQwqPkvKQHp3F+MhU077mM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=O2K+aOH8; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="O2K+aOH8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D44EC113D0; Sun, 23 Nov 2025 13:17:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763903864; bh=3UH0sUpcsTOMjRwBlMwUCGFDDjKFaDmhv/y2Ls/sfXU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=O2K+aOH8CH0SgIG5qkAKVKBBGA5eKkh3RnxoxnzDXEB39VO7sKffUoMENpcavfnps +3G108dSrTGGkK6l+sHK5SKGat8idVDagp0VLT5RFHAN4fx8SD9xp6nsE9kHmJ1m7a yB60iAQX+2i7FuKGFtIOYh3O3TuWeYaowik+X8dTX6bahRATEELN1OSWldkowv3z3X xvsInynJh9iB6iwgTkJ1D2RULkuryOUftJ45zxbHXQ2h9lZVlqbuh1By4UjoIbMSve nvzKjQAeLIBGnEpTyAZg6rfoxw92k+s1mS3FdNTPNYWCvWa/3LuqDctZy3TbpWYmUP o0a4RG7zYDYQw== Message-ID: <10a90b15-3e26-451a-bebf-f7ad8ba67d1b@kernel.org> Date: Sun, 23 Nov 2025 14:17:37 +0100 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 v9 2/7] mm: introduce clear_pages() and clear_user_pages() To: Ankur Arora , linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Cc: akpm@linux-foundation.org, david@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, mjguzik@gmail.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, willy@infradead.org, raghavendra.kt@amd.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com References: <20251121202352.494700-1-ankur.a.arora@oracle.com> <20251121202352.494700-3-ankur.a.arora@oracle.com> From: "Christophe Leroy (CS GROUP)" Content-Language: fr-FR In-Reply-To: <20251121202352.494700-3-ankur.a.arora@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 21/11/2025 à 21:23, Ankur Arora a écrit : > Introduce clear_pages(), to be overridden by architectures that > support more efficient clearing of consecutive pages. > > Also introduce clear_user_pages(), however, we will not expect > this function to be overridden anytime soon. > > We have to place the clear_user_pages() variant that uses > clear_user_page() into mm/util.c for now to work around > macro magic on sparc and m68k. > > Signed-off-by: Ankur Arora > Acked-by: David Hildenbrand (Red Hat) > --- > > Notes: > - Use macros clear_pages, clear_user_page, instead of __HAVE_ARCH_CLEAR_PAGES, > __HAVE_ARCH_CLEAR_USER_PAGE. > > include/linux/mm.h | 41 +++++++++++++++++++++++++++++++++++++++++ > mm/util.c | 13 +++++++++++++ > 2 files changed, 54 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 6fa6c188f99a..c397ee2f6dd5 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3879,6 +3879,26 @@ static inline void clear_page_guard(struct zone *zone, struct page *page, > unsigned int order) {} > #endif /* CONFIG_DEBUG_PAGEALLOC */ > > +#ifndef clear_pages > +/** > + * clear_pages() - clear a page range for kernel-internal use. > + * @addr: start address > + * @npages: number of pages > + * > + * Use clear_user_pages() instead when clearing a page range to be > + * mapped to user space. > + * > + * Does absolutely no exception handling. > + */ > +static inline void clear_pages(void *addr, unsigned int npages) > +{ > + do { > + clear_page(addr); > + addr += PAGE_SIZE; > + } while (--npages); Why a 'do while' instead of a 'while' ? Are you certain that this function will never ever be called with a nul npages ? > +} > +#endif > + > #ifndef clear_user_page > /** > * clear_user_page() - clear a page to be mapped to user space > @@ -3901,6 +3921,27 @@ static inline void clear_user_page(void *addr, unsigned long vaddr, struct page > } > #endif > > +/** > + * clear_user_pages() - clear a page range to be mapped to user space > + * @addr: start address > + * @vaddr: start address of the user mapping > + * @page: start page > + * @npages: number of pages > + * > + * Assumes that the region (@addr, +@npages) has been validated > + * already so this does no exception handling. > + */ > +#ifdef clear_user_pages > +void clear_user_pages(void *addr, unsigned long vaddr, > + struct page *page, unsigned int npages); By doing this you forbid architectures to define it as a static inline, is that wanted ? > +#else > +static inline void clear_user_pages(void *addr, unsigned long vaddr, > + struct page *page, unsigned int npages) > +{ > + clear_pages(addr, npages); > +} > +#endif > + > #ifdef __HAVE_ARCH_GATE_AREA > extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm); > extern int in_gate_area_no_mm(unsigned long addr); > diff --git a/mm/util.c b/mm/util.c > index 8989d5767528..3c6cd44db1bd 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -1344,3 +1344,16 @@ bool page_range_contiguous(const struct page *page, unsigned long nr_pages) > } > EXPORT_SYMBOL(page_range_contiguous); > #endif > + > +#ifdef clear_user_page > +void clear_user_pages(void *addr, What happens if clear_user_page is defined but not clear_user_pages ? In that case it seems like the definition in linux/mm.h will conflict. unsigned long vaddr, > + struct page *page, unsigned int npages) > +{ > + do { > + clear_user_page(addr, vaddr, page); > + addr += PAGE_SIZE; > + vaddr += PAGE_SIZE; > + page++; > + } while (--npages); Same, are you sure npages will never be nul ? > +} > +#endif