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Wythe" Cc: Uladzislau Rezki , "David S. Miller" , Andrew Morton , Dust Li , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Sidraya Jayagond , Wenjia Zhang , Mahanta Jambigi , Simon Horman , Tony Lu , Wen Gu , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, oliver.yang@linux.alibaba.com Subject: Re: [PATCH net-next 2/3] mm: vmalloc: export find_vm_area() Message-ID: References: <20260123082349.42663-1-alibuda@linux.alibaba.com> <20260123082349.42663-3-alibuda@linux.alibaba.com> <20260124093505.GA98529@j66a10360.sqa.eu95> Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260124093505.GA98529@j66a10360.sqa.eu95> Hello, D. Wythe! > On Fri, Jan 23, 2026 at 07:55:17PM +0100, Uladzislau Rezki wrote: > > On Fri, Jan 23, 2026 at 04:23:48PM +0800, D. Wythe wrote: > > > find_vm_area() provides a way to find the vm_struct associated with a > > > virtual address. Export this symbol to modules so that modularized > > > subsystems can perform lookups on vmalloc addresses. > > > > > > Signed-off-by: D. Wythe > > > --- > > > mm/vmalloc.c | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > > index ecbac900c35f..3eb9fe761c34 100644 > > > --- a/mm/vmalloc.c > > > +++ b/mm/vmalloc.c > > > @@ -3292,6 +3292,7 @@ struct vm_struct *find_vm_area(const void *addr) > > > > > > return va->vm; > > > } > > > +EXPORT_SYMBOL_GPL(find_vm_area); > > > > > This is internal. We can not just export it. > > > > -- > > Uladzislau Rezki > > Hi Uladzislau, > > Thank you for the feedback. I agree that we should avoid exposing > internal implementation details like struct vm_struct to external > subsystems. > > Following Christoph's suggestion, I'm planning to encapsulate the page > order lookup into a minimal helper instead: > > unsigned int vmalloc_page_order(const void *addr){ > struct vm_struct *vm; > vm = find_vm_area(addr); > return vm ? vm->page_order : 0; > } > EXPORT_SYMBOL_GPL(vmalloc_page_order); > > Does this approach look reasonable to you? It would keep the vm_struct > layout private while satisfying the optimization needs of SMC. > Could you please clarify why you need info about page_order? I have not looked at your second patch. Thanks! -- Uladzislau Rezki