From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt1-f199.google.com (mail-qt1-f199.google.com [209.85.160.199]) by kanga.kvack.org (Postfix) with ESMTP id 3C3CF6B000A for ; Fri, 5 Oct 2018 06:49:54 -0400 (EDT) Received: by mail-qt1-f199.google.com with SMTP id f19-v6so11703905qtp.6 for ; Fri, 05 Oct 2018 03:49:54 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id l13-v6sor5936616qvi.64.2018.10.05.03.49.52 for (Google Transport Security); Fri, 05 Oct 2018 03:49:52 -0700 (PDT) MIME-Version: 1.0 References: <20181003185854.GA1174@jordon-HP-15-Notebook-PC> <20181003200003.GA9965@bombadil.infradead.org> <20181003221444.GZ30658@n2100.armlinux.org.uk> <20181004123400.GC30658@n2100.armlinux.org.uk> <20181004181736.GB20842@bombadil.infradead.org> In-Reply-To: From: Miguel Ojeda Date: Fri, 5 Oct 2018 12:49:41 +0200 Message-ID: Subject: Re: [PATCH v2] mm: Introduce new function vm_insert_kmem_page Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Souptick Joarder Cc: Matthew Wilcox , linux@armlinux.org.uk, Robin van der Gracht , stefanr@s5r6.in-berlin.de, hjc@rock-chips.com, =?UTF-8?Q?Heiko_St=C3=BCbner?= , Dave Airlie , robin.murphy@arm.com, iamjoonsoo.kim@lge.com, Andrew Morton , Marek Szyprowski , Kees Cook , treding@nvidia.com, mhocko@suse.com, Dan Williams , kirill.shutemov@linux.intel.com, Mark Rutland , Andrey Ryabinin , Dmitry Vyukov , Kate Stewart , tchibo@google.com, riel@redhat.com, minchan@kernel.org, Peter Zijlstra , ying.huang@intel.com, Andi Kleen , rppt@linux.vnet.ibm.com, Dominik Brodowski , Arnd Bergmann , cpandya@codeaurora.org, hannes@cmpxchg.org, Joe Perches , mcgrof@kernel.org, Linux ARM , linux-kernel , linux1394-devel@lists.sourceforge.net, dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, Linux-MM Hi Souptick, On Fri, Oct 5, 2018 at 12:01 PM Souptick Joarder wrote: > > The final goal is to remove vm_insert_page by converting it to > vmf_insert_page. But to do that we have to first introduce the > new API which is similar to vm_insert_page (for non #PF). I tried this by > introducing vm_insert_kmem_page ( * identical as vm_insert_page > except API name *) in this patch. But this looks like a bad approach. We are going in circles here. That you want to convert vm_insert_page to vmf_insert_page for the PF case is fine and understood. However, you don't *need* to introduce a new name for the remaining non-PF cases if the function is going to be the exact same thing as before. You say "The final goal is to remove vm_insert_page", but you haven't justified *why* you need to remove that name. Now, if we want to rename the function for some reason (e.g. avoid confusion with vmf_insert_page), that is fine but is another topic. It may be or not a good idea, but it is orthogonal to the vmf_ work. Matthew, on this regard, told you that you shouldn't duplicate functions. If you want a rename, do so; but don't copy the code. In other words: nobody said introducing the vm_insert_kmem_page name is a bad idea -- what Matthew told you is that *duplicating* vm_insert_page just for that is bad. Further, you are copying the code (if I understand your thought process) because you want to change the callers of non-PF first, and then do the "full conversion from vm_* to vmf_*". However, that is confusing, because there is no need to change non-PF callers of vm_insert_page since they don't care about the new vmf_* functions. Instead, the proper way of doing this is: 1. Introduce the vmf_* API 2. Change all PF-users users to that (leaving all non-PF ones untouched!) -- if this is too big, you can split this patch into several patches, one per subsystem, etc. 3. Remove the vm_* functions (except the ones that are still used in non-PF contexts, e.g. vm_insert_page) Then, optionally, if you want to rename the function for the remaining non-PF users: 4. Rename vm_insert_page (justifying why the current name is confusing *on its own merits*). Otherwise, if you want to pursue Matthew's idea: 4. Introduce the vm_insert_range (possibly leveraging vm_insert_page, or not; you have to see what is best). 5. Replace those callers that can take advantage of vm_insert_range 6. Remove vm_insert_page and replace callers with vm_insert_range (only if it is not worth to keep vm_insert_range, again justifying it *on its own merits*) As you see, these are all logical step-by-step improvements, without duplicating functions temporarily, leaving temporary changes or changing current callers to new APIs for unrelated reasons (i.e. no need to introduce vm_insert_kmem_page simply to do a "conversion" to vmf_). Cheers, Miguel