[PATCH v7 5/6] udmabuf: Pin the pages using memfd_pin_folios() API (v5)

[Vivek Kasireddy]

Using memfd_pin_folios() will ensure that the pages are pinned
correctly using FOLL_PIN. And, this also ensures that we don't
accidentally break features such as memory hotunplug as it would
not allow pinning pages in the movable zone.

Using this new API also simplifies the code as we no longer have
to deal with extracting individual pages from their mappings or
handle shmem and hugetlb cases separately.

v2:
- Adjust to the change in signature of pin_user_pages_fd() by
  passing in file * instead of fd.

v3:
- Limit the changes in this patch only to those that are required
  for using pin_user_pages_fd()
- Slightly improve the commit message

v4:
- Adjust to the change in name of the API (memfd_pin_user_pages)

v5:
- Adjust to the changes in memfd_pin_folios which now populates
  a list of folios and offsets

Cc: David Hildenbrand <david at redhat.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Mike Kravetz <mike.kravetz at oracle.com>
Cc: Hugh Dickins <hughd at google.com>
Cc: Peter Xu <peterx at redhat.com>
Cc: Jason Gunthorpe <jgg at nvidia.com>
Cc: Gerd Hoffmann <kraxel at redhat.com>
Cc: Dongwon Kim <dongwon.kim at intel.com>
Cc: Junxiao Chang <junxiao.chang at intel.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy at intel.com>
---
 drivers/dma-buf/udmabuf.c | 85 ++++++---------------------------------
 1 file changed, 12 insertions(+), 73 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index e1b8da3c9b2a..a614e720837d 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -42,7 +42,7 @@ static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)
 	if (pgoff >= ubuf->pagecount)
 		return VM_FAULT_SIGBUS;
 
-	pfn = page_to_pfn(&ubuf->folios[pgoff]->page);
+	pfn = page_to_pfn(folio_page(ubuf->folios[pgoff], 0));
 	pfn += ubuf->offsets[pgoff] >> PAGE_SHIFT;
 
 	return vmf_insert_pfn(vma, vmf->address, pfn);
@@ -79,7 +79,7 @@ static int vmap_udmabuf(struct dma_buf *buf, struct iosys_map *map)
 		return -ENOMEM;
 
 	for (pg = 0; pg < ubuf->pagecount; pg++)
-		pages[pg] = &ubuf->folios[pg]->page;
+		pages[pg] = folio_page(ubuf->folios[pg], 0);
 
 	vaddr = vm_map_ram(pages, ubuf->pagecount, -1);
 	kfree(pages);
@@ -163,7 +163,8 @@ static void release_udmabuf(struct dma_buf *buf)
 		put_sg_table(dev, ubuf->sg, DMA_BIDIRECTIONAL);
 
 	for (pg = 0; pg < ubuf->pagecount; pg++)
-		folio_put(ubuf->folios[pg]);
+		unpin_user_page(folio_page(ubuf->folios[pg], 0));
+
 	kfree(ubuf->offsets);
 	kfree(ubuf->folios);
 	kfree(ubuf);
@@ -218,65 +219,6 @@ static const struct dma_buf_ops udmabuf_ops = {
 #define SEALS_WANTED (F_SEAL_SHRINK)
 #define SEALS_DENIED (F_SEAL_WRITE)
 
-static int handle_hugetlb_pages(struct udmabuf *ubuf, struct file *memfd,
-				pgoff_t offset, pgoff_t pgcnt,
-				pgoff_t *pgbuf)
-{
-	struct hstate *hpstate = hstate_file(memfd);
-	pgoff_t mapidx = offset >> huge_page_shift(hpstate);
-	pgoff_t subpgoff = (offset & ~huge_page_mask(hpstate)) >> PAGE_SHIFT;
-	pgoff_t maxsubpgs = huge_page_size(hpstate) >> PAGE_SHIFT;
-	struct folio *folio = NULL;
-	pgoff_t pgidx;
-
-	mapidx <<= huge_page_order(hpstate);
-	for (pgidx = 0; pgidx < pgcnt; pgidx++) {
-		if (!folio) {
-			folio = __filemap_get_folio(memfd->f_mapping,
-						    mapidx,
-						    FGP_ACCESSED, 0);
-			if (IS_ERR(folio))
-				return PTR_ERR(folio);
-		}
-
-		folio_get(folio);
-		ubuf->folios[*pgbuf] = folio;
-		ubuf->offsets[*pgbuf] = subpgoff << PAGE_SHIFT;
-		(*pgbuf)++;
-		if (++subpgoff == maxsubpgs) {
-			folio_put(folio);
-			folio = NULL;
-			subpgoff = 0;
-			mapidx += pages_per_huge_page(hpstate);
-		}
-	}
-
-	if (folio)
-		folio_put(folio);
-
-	return 0;
-}
-
-static int handle_shmem_pages(struct udmabuf *ubuf, struct file *memfd,
-			      pgoff_t offset, pgoff_t pgcnt,
-			      pgoff_t *pgbuf)
-{
-	pgoff_t pgidx, pgoff = offset >> PAGE_SHIFT;
-	struct folio *folio = NULL;
-
-	for (pgidx = 0; pgidx < pgcnt; pgidx++) {
-		folio = shmem_read_folio(memfd->f_mapping,
-					 pgoff + pgidx);
-		if (IS_ERR(folio))
-			return PTR_ERR(folio);
-
-		ubuf->folios[*pgbuf] = folio;
-		(*pgbuf)++;
-	}
-
-	return 0;
-}
-
 static int check_memfd_seals(struct file *memfd)
 {
 	int seals;
@@ -325,7 +267,7 @@ static long udmabuf_create(struct miscdevice *device,
 	pgoff_t pgcnt, pgbuf = 0, pglimit;
 	struct file *memfd = NULL;
 	struct udmabuf *ubuf;
-	int ret = -EINVAL;
+	long ret = -EINVAL;
 	u32 i, flags;
 
 	ubuf = kzalloc(sizeof(*ubuf), GFP_KERNEL);
@@ -366,17 +308,13 @@ static long udmabuf_create(struct miscdevice *device,
 			goto err;
 
 		pgcnt = list[i].size >> PAGE_SHIFT;
-		if (is_file_hugepages(memfd))
-			ret = handle_hugetlb_pages(ubuf, memfd,
-						   list[i].offset,
-						   pgcnt, &pgbuf);
-		else
-			ret = handle_shmem_pages(ubuf, memfd,
-						 list[i].offset,
-						 pgcnt, &pgbuf);
+		ret = memfd_pin_folios(memfd, list[i].offset, pgcnt,
+				       ubuf->folios + pgbuf,
+				       ubuf->offsets + pgbuf);
 		if (ret < 0)
 			goto err;
 
+		pgbuf += pgcnt;
 		fput(memfd);
 		memfd = NULL;
 	}
@@ -389,8 +327,9 @@ static long udmabuf_create(struct miscdevice *device,
 	return ret;
 
 err:
-	while (pgbuf > 0)
-		folio_put(ubuf->folios[--pgbuf]);
+	while (pgbuf-- > 0)
+		if (ubuf->folios[pgbuf])
+			unpin_user_page(folio_page(ubuf->folios[pgbuf], 0));
 	if (memfd)
 		fput(memfd);
 	kfree(ubuf->offsets);
-- 
2.39.2