Hi Huan,
> Subject: [PATCH v3 3/5] fix vmap_udmabuf error page set
Please prepend a "udmabuf:" to the subject line and improve the wording.
>
> 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.
>
> Signed-off-by: Huan Yang <link@xxxxxxxx>
> Suggested-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
> ---
> drivers/dma-buf/udmabuf.c | 22 +++++++++++++++-------
> 1 file changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
> index 3ec72d47bb1c..4ec54c60d76c 100644
> --- a/drivers/dma-buf/udmabuf.c
> +++ b/drivers/dma-buf/udmabuf.c
> @@ -67,21 +67,29 @@ 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;
I wish there was a way to easily test the vmap scenario but its great that
you are able to eliminate the usage of "struct page" completely from
udmabuf driver, with this patch.
> 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);
Looks like this would require a "select VMAP_PFN" in Kconfig.
Thanks,
Vivek
> + kvfree(pfns);
> if (!vaddr)
> return -EINVAL;
>
> --
> 2.45.2
