Hi Huan,
> Subject: [PATCH v6 3/7] udmabuf: fix vmap_udmabuf error page set
>
> Currently vmap_udmabuf set page's array by each folio.
> But, ubuf->folios is only contain's the folio's head page.
>
> That mean we repeatedly mapped the folio head page to the vmalloc area.
>
> Due to udmabuf can use hugetlb, if HVO enabled, tail page may not exist,
> so, we can't use page array to map, instead, use pfn array.
>
> By this, we removed page usage in udmabuf totally.
>
I think this would probably need a Fixes tag:
Fixes: 5e72b2b41a21 ("udmabuf: convert udmabuf driver to use folios")
Thanks,
Vivek
> Suggested-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
> Signed-off-by: Huan Yang <link@xxxxxxxx>
> Acked-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
> ---
> drivers/dma-buf/Kconfig | 1 +
> drivers/dma-buf/udmabuf.c | 22 +++++++++++++++-------
> 2 files changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig
> index b46eb8a552d7..fee04fdb0822 100644
> --- a/drivers/dma-buf/Kconfig
> +++ b/drivers/dma-buf/Kconfig
> @@ -36,6 +36,7 @@ config UDMABUF
> depends on DMA_SHARED_BUFFER
> depends on MEMFD_CREATE || COMPILE_TEST
> depends on MMU
> + select VMAP_PFN
> help
> A driver to let userspace turn memfd regions into dma-bufs.
> Qemu can use this to create host dmabufs for guest framebuffers.
> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
> index ba9dbc7caf71..aa182a9dcdfa 100644
> --- a/drivers/dma-buf/udmabuf.c
> +++ b/drivers/dma-buf/udmabuf.c
> @@ -103,21 +103,29 @@ static int mmap_udmabuf(struct dma_buf *buf,
> struct vm_area_struct *vma)
> static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
> {
> struct udmabuf *ubuf = buf->priv;
> - struct page **pages;
> + unsigned long *pfns;
> void *vaddr;
> pgoff_t pg;
>
> dma_resv_assert_held(buf->resv);
>
> - pages = kvmalloc_array(ubuf->pagecount, sizeof(*pages),
> GFP_KERNEL);
> - if (!pages)
> + /**
> + * HVO may free tail pages, so just use pfn to map each folio
> + * into vmalloc area.
> + */
> + pfns = kvmalloc_array(ubuf->pagecount, sizeof(*pfns), GFP_KERNEL);
> + if (!pfns)
> return -ENOMEM;
>
> - for (pg = 0; pg < ubuf->pagecount; pg++)
> - pages[pg] = &ubuf->folios[pg]->page;
> + for (pg = 0; pg < ubuf->pagecount; pg++) {
> + unsigned long pfn = folio_pfn(ubuf->folios[pg]);
>
> - vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
> - kvfree(pages);
> + pfn += ubuf->offsets[pg] >> PAGE_SHIFT;
> + pfns[pg] = pfn;
> + }
> +
> + vaddr = vmap_pfn(pfns, ubuf->pagecount, PAGE_KERNEL);
> + kvfree(pfns);
> if (!vaddr)
> return -EINVAL;
>
> --
> 2.45.2
