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Wythe" To: Uladzislau Rezki Cc: "D. Wythe" , "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: <20260124093505.GA98529@j66a10360.sqa.eu95> References: <20260123082349.42663-1-alibuda@linux.alibaba.com> <20260123082349.42663-3-alibuda@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Rspamd-Queue-Id: 1B6F1180009 X-Stat-Signature: btgj4wqja4me4pwrmzcrdhsqi9baf4ex X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1769247309-128770 X-HE-Meta: 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 BmVKVM5B X8dhvI8FrqBslRSP7VqiMfomslZCKN9rAOYjkHTja3yuD3AmIp7anZ+LfKKkDgcqqiTkZL6NX/F6HHd74vb88Jedujfm67w2E3QU1HLKoAo2RNeZrx6R6iduLd/CET/Toqggiw/U92YO/36salk9oP0eXgpPjHu1TQxFDO5y8IL0NvtpCFDdN//lHKWcJ88fTjW2mBwtQ5XhchXZvw8ABi0hHbRiZgiXM/lPdlbA+rgp/MzWjEiUdHV4OVSLTuVUoMuaRyIb1uDE902Y= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. Thanks, D. Wythe