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Mon, 19 Jan 2026 10:26:41 -0500 (EST) Date: Mon, 19 Jan 2026 15:26:37 +0000 From: Kiryl Shutsemau To: Muchun Song Cc: Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Andrew Morton , David Hildenbrand , Matthew Wilcox , Usama Arif , Frank van der Linden Subject: Re: [PATCHv3 09/15] mm/hugetlb: Refactor code around vmemmap_walk Message-ID: References: <20260115144604.822702-1-kas@kernel.org> <20260115144604.822702-10-kas@kernel.org> <72e04317-913e-4db1-89ed-61727bbdd01e@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <72e04317-913e-4db1-89ed-61727bbdd01e@linux.dev> On Mon, Jan 19, 2026 at 06:04:32PM +0800, Muchun Song wrote: > > @@ -415,29 +377,27 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end, > > * to remap. > > * @end: end address of the vmemmap virtual address range that we want to > > * remap. > > - * @reuse: reuse address. > > * @flags: modifications to vmemmap_remap_walk flags > > * > > * Return: %0 on success, negative error code otherwise. > > */ > > static int vmemmap_remap_alloc(unsigned long start, unsigned long end, > > - unsigned long reuse, unsigned long flags) > > + unsigned long flags) > > { > > LIST_HEAD(vmemmap_pages); > > struct vmemmap_remap_walk walk = { > > .remap_pte = vmemmap_restore_pte, > > - .reuse_addr = reuse, > > + .vmemmap_start = start, > > .vmemmap_pages = &vmemmap_pages, > > .flags = flags, > > }; > > - /* See the comment in the vmemmap_remap_free(). */ > > - BUG_ON(start - reuse != PAGE_SIZE); > > + start += HUGETLB_VMEMMAP_RESERVE_SIZE; > > From the @start comment above this function, we can see that the @start > address is the starting address for the remap operation we want to perform. > However, the modification here does not conform to the semantics here. > Therefore, I suggest letting the caller __hugetlb_vmemmap_restore_folio() > pass the correct parameters itself. > > The reason we previously used the reuse address here is that the > initialization of ->reuse_page was inside vmemmap_pte_entry. Now, > ->reuse_page has been removed in your patch. Fair enough. > > @@ -466,18 +425,16 @@ static int __hugetlb_vmemmap_restore_folio(const struct hstate *h, > > if (flags & VMEMMAP_SYNCHRONIZE_RCU) > > synchronize_rcu(); > > + vmemmap_start = (unsigned long)folio; > > (unsigned long)&folio->page？The folio is the metadata for contiguous pages, > while the page is our optimization target. Although their values are the > same now, their semantics are different. Okay. -- Kiryl Shutsemau / Kirill A. Shutemov