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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=l18hC4xT/sUPl8dCaDqcr/Ljf4Uj9z5GidEBxYlDB+Za59H+9rQjYDbLJFszRBqYW PxjxqhsMi5uQxLcE4Nl/DuuoVFXXxhLjquX1Os0uGlFuFAuY9NJJW5nS3LunIq6U9n qnX+Oi/SN60p8p0hOGnN7SN2AjE0Cqe1N/bsuZak= Message-ID: <54434a84-51b3-4e3f-988b-6bcbac5a2f42@arm.com> Date: Mon, 13 Jul 2026 20:43:14 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 0/6] mm/vmalloc: Speed up ioremap, vmalloc and vmap with contiguous memory To: Wen Jiang , Andrew Morton Cc: catalin.marinas@arm.com, linux-mm@kvack.org, urezki@gmail.com, will@kernel.org, Xueyuan.chen21@gmail.com, ajd@linux.ibm.com, anshuman.khandual@arm.com, david@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, rppt@kernel.org, ryan.roberts@arm.com, Wen Jiang References: <20260709073823.6643-1-jiangwen6@xiaomi.com> <20260709160805.26e63bae89dd03cf2951104e@linux-foundation.org> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: kcy1do5iu418q694nhdte6qxuyfx3bnp X-Rspamd-Queue-Id: 6BC4D1C0004 X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1783955601-54 X-HE-Meta: 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 5/sRV+g8 qLpHNxkbMPheAmCWPqr8ck/9+JjY+e8RvX2REvyqkhEfs46phze8AKcWMrCYC5Qt86m0YzIdIfDJKC/ixq7nrzjeXyRhw5ybEeoQbCE3OzaZiHf09aphVYqe64+5OKnvov5NPnMtHJdUm12u6cub0XsUGj5tukxTY8XdAVBP2kow2XSjw0NgHSJMWywu95BdLc2fb2pftqm+qBqvMHq6TcDGxsjHtEIpIFdI2hV2zW86AZTyNS9s+CKe23ENdH6oeCifSWgFEtOYgF/HoiPEGSnMJmKwk6YLiG4pYRWkQahhfOTeYQIL7QYynRJKeUnVi3fYipLBf2W+MR/7JtAokQbFBtfb3+11KxFazHid78wgYVF9r32iaoiAuqFg1yX2EyjkZhaOFVBk+9aGA4CZq9Zra7VlwKRNBuhZVtZ507MeFxg9/xNVKhIBTTXizIKYE/yy1YcJKdNhtXsqExh9CVXar9pWFegb7q48u Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/07/26 2:24 pm, Wen Jiang wrote: > On Fri, 10 Jul 2026 at 07:08, Andrew Morton wrote: >> >> On Thu, 9 Jul 2026 15:38:17 +0800 Wen Jiang wrote: >> >>> This patchset accelerates ioremap, vmalloc, and vmap when the memory >>> is physically fully or partially contiguous. >> >> Thanks, I added this to mm.git's mm-new branch for wider testing. >> >> AI review asked some questions, and some of them are new since the v5 >> series: >> https://sashiko.dev/#/patchset/20260709073823.6643-1-jiangwen6@xiaomi.com > > Hi Andrew, > > I've gone through the Sashiko findings: > > - Patch 1 (find_num_contig): Over-interpretation. No new hugetlbfs hstate > is added. The extra sizes are only used by init_mm kernel mappings via. > > - Patch 5/6 (NULL page): Invalid input. vmap() expects a fully populated > array of valid struct page pointers. Correct, but vmap_pages_pte_range has !page and !pfn_valid checks. I really hate those checks - if those checks have any remote possibility of firing, then we already have a bug at vm_map_ram -> vmap_pages_range -> vmap_pages_range_noflush -> kmsan_vmap_pages_range_noflush because the last function dereferences the struct page pointers. It is painful to do the page array sanity check deep into vmap - it implies we simply cannot play with the page array before that. But since vmap is an exported function, doing a sanity check for the page array in the vmap code makes sense. So how about the following: diff --git a/mm/vmalloc.c b/mm/vmalloc.c index afaa14ebf17bb..0c44bb7a45b5d 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -566,14 +566,6 @@ static int vmap_pages_pte_range(pmd_t *pmd, unsigned long addr, err = -EBUSY; break; } - if (WARN_ON(!page)) { - err = -ENOMEM; - break; - } - if (WARN_ON(!pfn_valid(page_to_pfn(page)))) { - err = -EINVAL; - break; - } pfn = page_to_pfn(page); size = vmap_set_ptes(pte, addr, end, pfn, prot, shift); @@ -603,11 +595,6 @@ static int vmap_pages_pmd_range(pud_t *pud, unsigned long addr, struct page *page = pages[*nr]; phys_addr_t phys_addr; - if (WARN_ON(!page)) - return -ENOMEM; - if (WARN_ON(!pfn_valid(page_to_pfn(page)))) - return -EINVAL; - phys_addr = page_to_phys(page); if (vmap_try_huge_pmd(pmd, addr, next, phys_addr, prot, @@ -3663,6 +3650,19 @@ static struct vm_struct *vmap_get_aligned_vm_area(unsigned long size, return __get_vm_area_node_aligned_caller(size, PAGE_SIZE, flags, caller); } +static inline bool vmap_page_sanity_checks(struct page **pages, unsigned int count) +{ + for (int i = 0; i < count; ++i) { + if (WARN_ON(!pages[i])) + return true; + + if (WARN_ON(!pfn_valid(page_to_pfn(pages[i])))) + return true; + } + + return false; +} + /** * vmap - map an array of pages into virtually contiguous space * @pages: array of page pointers @@ -3706,6 +3706,9 @@ void *vmap(struct page **pages, unsigned int count, if (!area) return NULL; + if (unlikely(vmap_page_sanity_checks(pages, count))) + return NULL; + addr = (unsigned long)area->addr; if (vmap_pages_range_batched(addr, addr + size, pgprot_nx(prot), pages) < 0) { Reasoning for calling vmap_page_sanity_checks() before vmap_pages_range_batched, and not at the start of vmap: I am worried that since vmap() is already very fast, we may cause a regression: vmap() -> scan page array with linear map pointers -> vmap_get_aligned_vm_area (does memory allocation, throwing out the linear map VAs from cache and TLB) -> walk the pgtables and again access cold page array. Perhaps I am being very pedantic here. What do you think? > > - Patch 6 (32-bit count << PAGE_SHIFT overflow): Pre-existing. This was > already discussed in the V3 thread, and a separate fix was proposed > there. > > Thanks, > Wen >