From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1859CC55179 for ; Tue, 27 Oct 2020 08:06:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B228D20829 for ; Tue, 27 Oct 2020 08:06:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="Xy9/3e57" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2508672AbgJ0IGz (ORCPT ); Tue, 27 Oct 2020 04:06:55 -0400 Received: from mail-oo1-f68.google.com ([209.85.161.68]:42952 "EHLO mail-oo1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2894389AbgJ0IFP (ORCPT ); Tue, 27 Oct 2020 04:05:15 -0400 Received: by mail-oo1-f68.google.com with SMTP id l26so114740oop.9 for ; Tue, 27 Oct 2020 01:05:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=iRVTkxIJnHwaBLHokGGgZRE0TJVDnrQ64zJBBqMFGs0=; b=Xy9/3e579FMjjTLWAuxWgipn5uXab1XIWYf2dD59Ue8ydsa3nziuf3dnpX6I3eKQXi LX0Fhct8zwQ9LPuwvLWtj2sHUJJ3/cbghGd13edFhR4n655CEK2nlwMk9XgeGlojhrCH MtcfG6S4mtBZzrOUEzua2bUtpL2rn4D1Bjj1E= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=iRVTkxIJnHwaBLHokGGgZRE0TJVDnrQ64zJBBqMFGs0=; b=KcixMx76Gs5YRoN0dl7awYt+oIfuicDt56VrbcTMKMlzxtEhUzvQhhhANJQ8sdqyDY vlf1CaHVRNMNfeD9FS1hjwDe5ouJiwLHAirgF26Fd7VXwXtt/cacQIyC4L6ODvSSP6Kp HgNTaLzFdo5zwVdFeRwyI4QMqIWxWeoPVsk64bvOGmyrgpOsY574t5M+VumLlrmGApFv ThuOwwEU5KhjmWXKUUJM7JRHX7/GUJkwyU65AkCwDal8yDE1RyQqoaThSYPfClaqcxWD SHwPts1O/dmKQxBObydCavWSrdfkrpD4JaPQgR04npArlr8hHG2VZpMR2IkD2SjR+F8j iKiA== X-Gm-Message-State: AOAM532gT+MtmhFlalnCLK7WTtwN+CUGI5d1OT4Cj/39FvlbtpODQnq/ HseylzHNNZ8jSESWaUATWA+WVmTKXCVk+ZpDa6IAYw== X-Google-Smtp-Source: ABdhPJwUquARZelitGIpZLDuhwl8Qo3TUgFyzzaUCWDMIxNpoISTQyK7JTuU9JW1uR1xbLdlZOvSwHCimNolpOBBW1c= X-Received: by 2002:a4a:b503:: with SMTP id r3mr809275ooo.28.1603785913727; Tue, 27 Oct 2020 01:05:13 -0700 (PDT) MIME-Version: 1.0 References: <20201026105818.2585306-1-daniel.vetter@ffwll.ch> <20201026105818.2585306-6-daniel.vetter@ffwll.ch> <20201026221520.GC2802004@chromium.org> In-Reply-To: <20201026221520.GC2802004@chromium.org> From: Daniel Vetter Date: Tue, 27 Oct 2020 09:05:01 +0100 Message-ID: Subject: Re: [PATCH v4 05/15] mm/frame-vector: Use FOLL_LONGTERM To: Tomasz Figa Cc: DRI Development , LKML , KVM list , Linux MM , Linux ARM , linux-samsung-soc , "open list:DMA BUFFER SHARING FRAMEWORK" , linux-s390 , Daniel Vetter , Jason Gunthorpe , Pawel Osciak , Marek Szyprowski , Kyungmin Park , Mauro Carvalho Chehab , Andrew Morton , John Hubbard , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jan Kara , Dan Williams Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-samsung-soc@vger.kernel.org On Mon, Oct 26, 2020 at 11:15 PM Tomasz Figa wrote: > > Hi Daniel, > > On Mon, Oct 26, 2020 at 11:58:08AM +0100, Daniel Vetter wrote: > > This is used by media/videbuf2 for persistent dma mappings, not just > > for a single dma operation and then freed again, so needs > > FOLL_LONGTERM. > > > > Unfortunately current pup_locked doesn't support FOLL_LONGTERM due to > > locking issues. Rework the code to pull the pup path out from the > > mmap_sem critical section as suggested by Jason. > > > > By relying entirely on the vma checks in pin_user_pages and follow_pfn > > (for vm_flags and vma_is_fsdax) we can also streamline the code a lot. > > > > Signed-off-by: Daniel Vetter > > Cc: Jason Gunthorpe > > Cc: Pawel Osciak > > Cc: Marek Szyprowski > > Cc: Kyungmin Park > > Cc: Tomasz Figa > > Cc: Mauro Carvalho Chehab > > Cc: Andrew Morton > > Cc: John Hubbard > > Cc: J=C3=A9r=C3=B4me Glisse > > Cc: Jan Kara > > Cc: Dan Williams > > Cc: linux-mm@kvack.org > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: linux-samsung-soc@vger.kernel.org > > Cc: linux-media@vger.kernel.org > > Signed-off-by: Daniel Vetter > > -- > > v2: Streamline the code and further simplify the loop checks (Jason) > > --- > > mm/frame_vector.c | 50 ++++++++++++++--------------------------------- > > 1 file changed, 15 insertions(+), 35 deletions(-) > > > > Thank you for the patch. Please see my comments inline. > > > diff --git a/mm/frame_vector.c b/mm/frame_vector.c > > index 10f82d5643b6..d44779e56313 100644 > > --- a/mm/frame_vector.c > > +++ b/mm/frame_vector.c > > @@ -38,7 +38,6 @@ int get_vaddr_frames(unsigned long start, unsigned in= t nr_frames, > > struct vm_area_struct *vma; > > int ret =3D 0; > > int err; > > - int locked; > > > > if (nr_frames =3D=3D 0) > > return 0; > > @@ -48,40 +47,25 @@ int get_vaddr_frames(unsigned long start, unsigned = int nr_frames, > > > > start =3D untagged_addr(start); > > > > - mmap_read_lock(mm); > > - locked =3D 1; > > - vma =3D find_vma_intersection(mm, start, start + 1); > > - if (!vma) { > > - ret =3D -EFAULT; > > - goto out; > > - } > > - > > - /* > > - * While get_vaddr_frames() could be used for transient (kernel > > - * controlled lifetime) pinning of memory pages all current > > - * users establish long term (userspace controlled lifetime) > > - * page pinning. Treat get_vaddr_frames() like > > - * get_user_pages_longterm() and disallow it for filesystem-dax > > - * mappings. > > - */ > > - if (vma_is_fsdax(vma)) { > > - ret =3D -EOPNOTSUPP; > > - goto out; > > - } > > - > > - if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) { > > + ret =3D pin_user_pages_fast(start, nr_frames, > > + FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM= , > > + (struct page **)(vec->ptrs)); > > + if (ret > 0) { > > vec->got_ref =3D true; > > vec->is_pfns =3D false; > > - ret =3D pin_user_pages_locked(start, nr_frames, > > - gup_flags, (struct page **)(vec->ptrs), &locked); > > Should we drop the gup_flags argument, since it's ignored now? Hm right I think an earlier version even had that, but then I moved to inlining the functionality in all the places it's used. I'll drop the gup flag. > > - goto out; > > + goto out_unlocked; > > } > > > > Should we initialize ret with 0 here, since pin_user_pages_fast() can > return a negative error code, but below we use it as a counter for the > looked up frames? Indeed, that's a bug. Will fix for v5. -Daniel > Best regards, > Tomasz > > > + mmap_read_lock(mm); > > vec->got_ref =3D false; > > vec->is_pfns =3D true; > > do { > > unsigned long *nums =3D frame_vector_pfns(vec); > > > > + vma =3D find_vma_intersection(mm, start, start + 1); > > + if (!vma) > > + break; > > + > > while (ret < nr_frames && start + PAGE_SIZE <=3D vma->vm_= end) { > > err =3D follow_pfn(vma, start, &nums[ret]); > > if (err) { > > @@ -92,17 +76,13 @@ int get_vaddr_frames(unsigned long start, unsigned = int nr_frames, > > start +=3D PAGE_SIZE; > > ret++; > > } > > - /* > > - * We stop if we have enough pages or if VMA doesn't comp= letely > > - * cover the tail page. > > - */ > > - if (ret >=3D nr_frames || start < vma->vm_end) > > + /* Bail out if VMA doesn't completely cover the tail page= . */ > > + if (start < vma->vm_end) > > break; > > - vma =3D find_vma_intersection(mm, start, start + 1); > > - } while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP)); > > + } while (ret < nr_frames); > > out: > > - if (locked) > > - mmap_read_unlock(mm); > > + mmap_read_unlock(mm); > > +out_unlocked: > > if (!ret) > > ret =3D -EFAULT; > > if (ret > 0) > > -- > > 2.28.0 > > --=20 Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch