On Fri, Oct 30, 2020 at 3:38 PM Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > > On Fri, Oct 30, 2020 at 3:11 PM Tomasz Figa <tfiga@xxxxxxxxxxxx> wrote: > > > > On Fri, Oct 30, 2020 at 11:08 AM Daniel Vetter <daniel.vetter@xxxxxxxx> 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 <daniel.vetter@xxxxxxxxx> > > > Cc: Jason Gunthorpe <jgg@xxxxxxxx> > > > Cc: Pawel Osciak <pawel@xxxxxxxxxx> > > > Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > > > Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> > > > Cc: Tomasz Figa <tfiga@xxxxxxxxxxxx> > > > Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx> > > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > > Cc: John Hubbard <jhubbard@xxxxxxxxxx> > > > Cc: Jérôme Glisse <jglisse@xxxxxxxxxx> > > > Cc: Jan Kara <jack@xxxxxxx> > > > Cc: Dan Williams <dan.j.williams@xxxxxxxxx> > > > Cc: linux-mm@xxxxxxxxx > > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > > > Cc: linux-samsung-soc@xxxxxxxxxxxxxxx > > > Cc: linux-media@xxxxxxxxxxxxxxx > > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > > > -- > > > v2: Streamline the code and further simplify the loop checks (Jason) > > > > > > v5: Review from Tomasz: > > > - fix page counting for the follow_pfn case by resetting ret > > > - drop gup_flags paramater, now unused > > > --- > > > .../media/common/videobuf2/videobuf2-memops.c | 3 +- > > > include/linux/mm.h | 2 +- > > > mm/frame_vector.c | 53 ++++++------------- > > > 3 files changed, 19 insertions(+), 39 deletions(-) > > > > > > > Thanks, looks good to me now. > > > > Acked-by: Tomasz Figa <tfiga@xxxxxxxxxxxx> > > > > From reading the code, this is quite unlikely to introduce any > > behavior changes, but just to be safe, did you have a chance to test > > this with some V4L2 driver? > > Nah, unfortunately not. I believe we don't have any setup that could exercise the IO/PFNMAP user pointers, but it should be possible to exercise the basic userptr path by enabling the virtual (fake) video driver, vivid or CONFIG_VIDEO_VIVID, in your kernel and then using yavta [1] with --userptr and --capture=<number of frames> (and possibly some more options) to grab a couple of frames from the test pattern generator. Does it sound like something that you could give a try? Feel free to ping me on IRC (tfiga on #v4l or #dri-devel) if you need any help. [1] https://git.ideasonboard.org/yavta.git Best regards, Tomasz > -Daniel > > > > > Best regards, > > Tomasz > > > > > diff --git a/drivers/media/common/videobuf2/videobuf2-memops.c b/drivers/media/common/videobuf2/videobuf2-memops.c > > > index 6e9e05153f4e..9dd6c27162f4 100644 > > > --- a/drivers/media/common/videobuf2/videobuf2-memops.c > > > +++ b/drivers/media/common/videobuf2/videobuf2-memops.c > > > @@ -40,7 +40,6 @@ struct frame_vector *vb2_create_framevec(unsigned long start, > > > unsigned long first, last; > > > unsigned long nr; > > > struct frame_vector *vec; > > > - unsigned int flags = FOLL_FORCE | FOLL_WRITE; > > > > > > first = start >> PAGE_SHIFT; > > > last = (start + length - 1) >> PAGE_SHIFT; > > > @@ -48,7 +47,7 @@ struct frame_vector *vb2_create_framevec(unsigned long start, > > > vec = frame_vector_create(nr); > > > if (!vec) > > > return ERR_PTR(-ENOMEM); > > > - ret = get_vaddr_frames(start & PAGE_MASK, nr, flags, vec); > > > + ret = get_vaddr_frames(start & PAGE_MASK, nr, vec); > > > if (ret < 0) > > > goto out_destroy; > > > /* We accept only complete set of PFNs */ > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > > index ef360fe70aaf..d6b8e30dce2e 100644 > > > --- a/include/linux/mm.h > > > +++ b/include/linux/mm.h > > > @@ -1765,7 +1765,7 @@ struct frame_vector { > > > struct frame_vector *frame_vector_create(unsigned int nr_frames); > > > void frame_vector_destroy(struct frame_vector *vec); > > > int get_vaddr_frames(unsigned long start, unsigned int nr_pfns, > > > - unsigned int gup_flags, struct frame_vector *vec); > > > + struct frame_vector *vec); > > > void put_vaddr_frames(struct frame_vector *vec); > > > int frame_vector_to_pages(struct frame_vector *vec); > > > void frame_vector_to_pfns(struct frame_vector *vec); > > > diff --git a/mm/frame_vector.c b/mm/frame_vector.c > > > index 10f82d5643b6..f8c34b895c76 100644 > > > --- a/mm/frame_vector.c > > > +++ b/mm/frame_vector.c > > > @@ -32,13 +32,12 @@ > > > * This function takes care of grabbing mmap_lock as necessary. > > > */ > > > int get_vaddr_frames(unsigned long start, unsigned int nr_frames, > > > - unsigned int gup_flags, struct frame_vector *vec) > > > + struct frame_vector *vec) > > > { > > > struct mm_struct *mm = current->mm; > > > struct vm_area_struct *vma; > > > int ret = 0; > > > int err; > > > - int locked; > > > > > > if (nr_frames == 0) > > > return 0; > > > @@ -48,40 +47,26 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, > > > > > > start = untagged_addr(start); > > > > > > - mmap_read_lock(mm); > > > - locked = 1; > > > - vma = find_vma_intersection(mm, start, start + 1); > > > - if (!vma) { > > > - ret = -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 = -EOPNOTSUPP; > > > - goto out; > > > - } > > > - > > > - if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) { > > > + ret = pin_user_pages_fast(start, nr_frames, > > > + FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM, > > > + (struct page **)(vec->ptrs)); > > > + if (ret > 0) { > > > vec->got_ref = true; > > > vec->is_pfns = false; > > > - ret = pin_user_pages_locked(start, nr_frames, > > > - gup_flags, (struct page **)(vec->ptrs), &locked); > > > - goto out; > > > + goto out_unlocked; > > > } > > > > > > + mmap_read_lock(mm); > > > vec->got_ref = false; > > > vec->is_pfns = true; > > > + ret = 0; > > > do { > > > unsigned long *nums = frame_vector_pfns(vec); > > > > > > + vma = find_vma_intersection(mm, start, start + 1); > > > + if (!vma) > > > + break; > > > + > > > while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) { > > > err = follow_pfn(vma, start, &nums[ret]); > > > if (err) { > > > @@ -92,17 +77,13 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, > > > start += PAGE_SIZE; > > > ret++; > > > } > > > - /* > > > - * We stop if we have enough pages or if VMA doesn't completely > > > - * cover the tail page. > > > - */ > > > - if (ret >= nr_frames || start < vma->vm_end) > > > + /* Bail out if VMA doesn't completely cover the tail page. */ > > > + if (start < vma->vm_end) > > > break; > > > - vma = 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 = -EFAULT; > > > if (ret > 0) > > > -- > > > 2.28.0 > > > > > _______________________________________________ > > dri-devel mailing list > > dri-devel@xxxxxxxxxxxxxxxxxxxxx > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch
