Revert "udmabuf: fix vmap_udmabuf error page set"

This reverts commit 18d7de823b7150344d242c3677e65d68c5271b04.

We cannot use vmap_pfn() in vmap_udmabuf() as it would fail the pfn_valid()
check in vmap_pfn_apply(). This is because vmap_pfn() is intended to be
used for mapping non-struct-page memory such as PCIe BARs. Since, udmabuf
mostly works with pages/folios backed by shmem/hugetlbfs/THP, vmap_pfn()
is not the right tool or API to invoke for implementing vmap.

Signed-off-by: Huan Yang <[e-mail]>
Suggested-by: Vivek Kasireddy <[e-mail]>
Reported-by: Bingbu Cao <[e-mail]>
Closes: https://lore.kernel.org/dri-devel/[e-mail]/T/#mbda4f64a3532b32e061f4e8763bc8e307bea3ca8
Acked-by: Vivek Kasireddy <[e-mail]>
Signed-off-by: Vivek Kasireddy <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/dma-buf/Kconfig

···
 	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.

drivers/dma-buf/udmabuf.c

···
 static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
 {
 	struct udmabuf *ubuf = buf->priv;
-	unsigned long *pfns;
+	struct page **pages;
 	void *vaddr;
 	pgoff_t pg;
 
 	dma_resv_assert_held(buf->resv);
 
-	/**
-	 * 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)
+	pages = kvmalloc_array(ubuf->pagecount, sizeof(*pages), GFP_KERNEL);
+	if (!pages)
 		return -ENOMEM;
 
-	for (pg = 0; pg < ubuf->pagecount; pg++) {
-		unsigned long pfn = folio_pfn(ubuf->folios[pg]);
+	for (pg = 0; pg < ubuf->pagecount; pg++)
+		pages[pg] = &ubuf->folios[pg]->page;
 
-		pfn += ubuf->offsets[pg] >> PAGE_SHIFT;
-		pfns[pg] = pfn;
-	}
-
-	vaddr = vmap_pfn(pfns, ubuf->pagecount, PAGE_KERNEL);
-	kvfree(pfns);
+	vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
+	kvfree(pages);
 	if (!vaddr)
 		return -EINVAL;