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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=mjdADVBavbIfoQjjnjGAOKAsOn2SXw9RUkr+c9HkpzsjGg5F87xy9VajsbDz/hcD6 uKVLLFNAx7UapzoLhWhvYbppY8tZqx610mKhSI2M1QU0flV3xrwBv3jOGyHyM0n4mC z1k1iHtkbnzeurZPkAHfsX9+cb2E+pFI9TkHTGgo= Message-ID: <945bdf1a-10f8-41fd-956e-af40af809c7b@arm.com> Date: Tue, 14 Jul 2026 12:15:45 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 4/6] mm/vmalloc: Extend page table walk to support larger page_shift sizes and eliminate page table rewalk To: Wen Jiang Cc: akpm@linux-foundation.org, 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, "Barry Song (Xiaomi)" , Wen Jiang , Leo Yan References: <20260709073823.6643-1-jiangwen6@xiaomi.com> <20260709073823.6643-5-jiangwen6@xiaomi.com> <85a3a79a-2a78-47ed-bd93-48e8f1967551@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 3592680002 X-Rspam-User: X-Stat-Signature: mzrmjqqhp8b3x5o5ay8tcymtcb1geszj X-Rspamd-Server: rspam03 X-HE-Tag: 1784011554-614506 X-HE-Meta: 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 Y0RyB/nB e+r2zW2fQFt4Un7v4NOQ+FGCCdX9XvbGloZbo/IY/vUIwn6Q7KnlNY+mcAZED4LxcanwDbL0QGp8ehPtMM/QlmC6dbSESvhAGuPr/W1Gvist/UdyAQzOs30F7X+IAWrb9dAAzr0enbr6CkEsfcZLxobKwHeH+ZaxLdSV7BtE4pRzuT43Ne/1eP6TYOykNVYMnTk6wv+1mNWwysL44zoTmwhwrwR5109Mks0gvVdVPmhLRuEw8e3lalGXSt6JSFMdDOe0ENkTxIcMl21tu11E8WrZ2eYnkPYxZc/1b2PdH9WG6ttRJrbsRG5qva7xVF8/Ls2GgF7L4QqaPA2LWHysEkA+5I/iZqVsq2KE12IWa6YnDRKovNDS5PR9dwJKMnGTIRc7qFSv97bSWY03WNZLrVasiOO/dO9bdbQ6KCANxs2M7fz6t4R3rFeGN9kAJ400yDR3d1YDUhdOK+fSGfWaGmSWrTQnBGaqw43/AYeTqbJq/9M0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 14/07/26 11:40 am, Wen Jiang wrote: > On Mon, 13 Jul 2026 at 21:49, Dev Jain wrote: >> >> >> >> On 09/07/26 1:08 pm, Wen Jiang wrote: >>> From: "Barry Song (Xiaomi)" >>> >>> vmap_pages_range_noflush_walk() (formerly vmap_small_pages_range_noflush()) >>> provides a clean interface by taking struct page **pages and mapping them >>> via direct PTE iteration. This avoids the page table rewalk seen when >>> using vmap_range_noflush() for page_shift values other than PAGE_SHIFT. >>> >>> Extend it to support larger page_shift values, and add PMD- and >>> contiguous-PTE mappings as well. Rename it to vmap_pages_range_noflush_walk() >>> since it now handles more than just small pages. >>> >>> For vmalloc() allocations with VM_ALLOW_HUGE_VMAP, we no longer need to >>> iterate over pages one by one via vmap_range_noflush(), which would >>> otherwise lead to page table rewalk. The code is now unified with the >>> PAGE_SHIFT case by simply calling vmap_pages_range_noflush_walk(). >>> >>> Signed-off-by: Barry Song (Xiaomi) >>> Signed-off-by: Wen Jiang >>> Tested-by: Xueyuan Chen >>> Tested-by: Leo Yan >>> Reviewed-by: Dev Jain >>> --- >>> mm/vmalloc.c | 81 ++++++++++++++++++++++++++++++---------------------- >>> 1 file changed, 47 insertions(+), 34 deletions(-) >>> >>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >>> index d7fef85b241c4..d2a4d649af549 100644 >>> --- a/mm/vmalloc.c >>> +++ b/mm/vmalloc.c >>> @@ -125,7 +125,8 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, >>> pte_t *pte; >>> u64 pfn; >>> struct page *page; >>> - unsigned long size = PAGE_SIZE; >>> + unsigned long size; >>> + unsigned int steps; >>> >>> if (WARN_ON_ONCE(!PAGE_ALIGNED(end - addr))) >>> return -EINVAL; >>> @@ -147,8 +148,8 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, >>> } >>> >>> size = vmap_set_ptes(pte, addr, end, pfn, prot, max_page_shift); >>> - pfn += PFN_DOWN(size); >>> - } while (pte += PFN_DOWN(size), addr += size, addr != end); >>> + steps = PFN_DOWN(size); >>> + } while (pte += steps, pfn += steps, addr += size, addr != end); >> >> I think I had also recommended to put these vmap_pte_range() changes >> into the previous patch. >> > > Hi Dev > > I put this change in patch 4 following Uladzislau's earlier suggestion: > > https://lore.kernel.org/linux-mm/ah3Cn3YnefIVJDo2@milan/ > > Uladzislau, do you have a preference on where this hunk should go? > Sorry if I wasn't clear enough. I am not contradicting Uladzislau's comment - separate patch 3 and 4 are good. I was just commenting on the specific change you did here w.r.t vmap_pte_range. The only bit you change above is to introduce a local variable 'steps'. You can move this bit into the previous patch, so that patch 4 is completely focussed on extending the vmap_pages_* functions to accept a 'shift'. > Thanks, > Wen