[PATCH v6 4/7] udmabuf: udmabuf_create pin folio codestyle cleanup

[Huan Yang]

This patch aims to simplify the pinning of folio during the udmabuf
creation. No functional changes.

This patch moves the memfd pin folio to udmabuf_pin_folios and modifies
the original loop condition, using the pinned folio as the external
loop condition, and sets the offset and folio during the traversal process.

By this, more readable.

Suggested-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
Signed-off-by: Huan Yang <link@xxxxxxxx>
---
 drivers/dma-buf/udmabuf.c | 134 +++++++++++++++++++++-----------------
 1 file changed, 76 insertions(+), 58 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index aa182a9dcdfa..fe1466f7d55a 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -328,17 +328,68 @@ static int export_udmabuf(struct udmabuf *ubuf,
 	return dma_buf_fd(buf, flags);
 }
 
+static long udmabuf_pin_folios(struct udmabuf *ubuf, struct file *memfd,
+			       loff_t start, loff_t size)
+{
+	pgoff_t pgoff, pgcnt, upgcnt = ubuf->pagecount;
+	struct folio **folios = NULL;
+	u32 cur_folio, cur_pgcnt;
+	long nr_folios;
+	long ret = 0;
+	loff_t end;
+
+	pgcnt = size >> PAGE_SHIFT;
+	folios = kvmalloc_array(pgcnt, sizeof(*folios), GFP_KERNEL);
+	if (!folios)
+		return -ENOMEM;
+
+	end = start + (pgcnt << PAGE_SHIFT) - 1;
+	nr_folios = memfd_pin_folios(memfd, start, end, folios, pgcnt, &pgoff);
+	if (nr_folios <= 0) {
+		ret = nr_folios ? nr_folios : -EINVAL;
+		goto end;
+	}
+
+	cur_pgcnt = 0;
+	for (cur_folio = 0; cur_folio < nr_folios; ++cur_folio) {
+		pgoff_t subpgoff = pgoff;
+		size_t fsize = folio_size(folios[cur_folio]);
+
+		ret = add_to_unpin_list(&ubuf->unpin_list, folios[cur_folio]);
+		if (ret < 0)
+			goto end;
+
+		for (; subpgoff < fsize; subpgoff += PAGE_SIZE) {
+			ubuf->folios[upgcnt] = folios[cur_folio];
+			ubuf->offsets[upgcnt] = subpgoff;
+			++upgcnt;
+
+			if (++cur_pgcnt >= pgcnt)
+				goto end;
+		}
+
+		/**
+		 * In a given range, only the first subpage of the first folio
+		 * has an offset, that is returned by memfd_pin_folios().
+		 * The first subpages of other folios (in the range) have an
+		 * offset of 0.
+		 */
+		pgoff = 0;
+	}
+end:
+	ubuf->pagecount = upgcnt;
+	kvfree(folios);
+	return ret;
+}
+
 static long udmabuf_create(struct miscdevice *device,
 			   struct udmabuf_create_list *head,
 			   struct udmabuf_create_item *list)
 {
-	pgoff_t pgoff, pgcnt, pglimit, pgbuf = 0;
-	long nr_folios, ret = -EINVAL;
-	struct file *memfd = NULL;
-	struct folio **folios;
+	pgoff_t pgcnt = 0, pglimit;
 	struct udmabuf *ubuf;
-	u32 i, j, k, flags;
-	loff_t end;
+	long ret = -EINVAL;
+	u32 i, flags;
 
 	ubuf = kzalloc(sizeof(*ubuf), GFP_KERNEL);
 	if (!ubuf)
@@ -347,81 +398,50 @@ static long udmabuf_create(struct miscdevice *device,
 	INIT_LIST_HEAD(&ubuf->unpin_list);
 	pglimit = (size_limit_mb * 1024 * 1024) >> PAGE_SHIFT;
 	for (i = 0; i < head->count; i++) {
-		if (!IS_ALIGNED(list[i].offset, PAGE_SIZE))
+		if (!PAGE_ALIGNED(list[i].offset))
 			goto err;
-		if (!IS_ALIGNED(list[i].size, PAGE_SIZE))
+		if (!PAGE_ALIGNED(list[i].size))
 			goto err;
-		ubuf->pagecount += list[i].size >> PAGE_SHIFT;
-		if (ubuf->pagecount > pglimit)
+
+		pgcnt += list[i].size >> PAGE_SHIFT;
+		if (pgcnt > pglimit)
 			goto err;
 	}
 
-	if (!ubuf->pagecount)
+	if (!pgcnt)
 		goto err;
 
-	ubuf->folios = kvmalloc_array(ubuf->pagecount, sizeof(*ubuf->folios),
-				      GFP_KERNEL);
+	ubuf->folios = kvmalloc_array(pgcnt, sizeof(*ubuf->folios), GFP_KERNEL);
 	if (!ubuf->folios) {
 		ret = -ENOMEM;
 		goto err;
 	}
-	ubuf->offsets = kvcalloc(ubuf->pagecount, sizeof(*ubuf->offsets),
-				 GFP_KERNEL);
+
+	ubuf->offsets = kvcalloc(pgcnt, sizeof(*ubuf->offsets), GFP_KERNEL);
 	if (!ubuf->offsets) {
 		ret = -ENOMEM;
 		goto err;
 	}
 
-	pgbuf = 0;
 	for (i = 0; i < head->count; i++) {
-		memfd = fget(list[i].memfd);
-		ret = check_memfd_seals(memfd);
-		if (ret < 0)
-			goto err;
+		struct file *memfd = fget(list[i].memfd);
 
-		pgcnt = list[i].size >> PAGE_SHIFT;
-		folios = kvmalloc_array(pgcnt, sizeof(*folios), GFP_KERNEL);
-		if (!folios) {
-			ret = -ENOMEM;
+		if (!memfd) {
+			ret = -EBADFD;
 			goto err;
 		}
 
-		end = list[i].offset + (pgcnt << PAGE_SHIFT) - 1;
-		ret = memfd_pin_folios(memfd, list[i].offset, end,
-				       folios, pgcnt, &pgoff);
-		if (ret <= 0) {
-			kvfree(folios);
-			if (!ret)
-				ret = -EINVAL;
+		ret = check_memfd_seals(memfd);
+		if (ret < 0) {
+			fput(memfd);
 			goto err;
 		}
 
-		nr_folios = ret;
-		pgoff >>= PAGE_SHIFT;
-		for (j = 0, k = 0; j < pgcnt; j++) {
-			ubuf->folios[pgbuf] = folios[k];
-			ubuf->offsets[pgbuf] = pgoff << PAGE_SHIFT;
-
-			if (j == 0 || ubuf->folios[pgbuf-1] != folios[k]) {
-				ret = add_to_unpin_list(&ubuf->unpin_list,
-							folios[k]);
-				if (ret < 0) {
-					kfree(folios);
-					goto err;
-				}
-			}
-
-			pgbuf++;
-			if (++pgoff == folio_nr_pages(folios[k])) {
-				pgoff = 0;
-				if (++k == nr_folios)
-					break;
-			}
-		}
-
-		kvfree(folios);
+		ret = udmabuf_pin_folios(ubuf, memfd, list[i].offset,
+					 list[i].size);
 		fput(memfd);
-		memfd = NULL;
+		if (ret)
+			goto err;
 	}
 
 	flags = head->flags & UDMABUF_FLAGS_CLOEXEC ? O_CLOEXEC : 0;
@@ -432,8 +452,6 @@ static long udmabuf_create(struct miscdevice *device,
 	return ret;
 
 err:
-	if (memfd)
-		fput(memfd);
 	unpin_all_folios(&ubuf->unpin_list);
 	kvfree(ubuf->offsets);
 	kvfree(ubuf->folios);
-- 
2.45.2