[PATCH v3 4/5] udmabuf: codestyle cleanup

[Huan Yang]

There are some variables in udmabuf_create that are only used inside the
loop. Therefore, there is no need to declare them outside the scope.
This patch moved it into loop.

It is difficult to understand the loop condition of the code that adds
folio to the unpin_list.

The outer loop of this patch iterates through folios, while the inner
loop correctly sets the folio and corresponding offset into the udmabuf
starting from the offset. if reach to pgcnt or nr_folios, end of loop.

By this, more readable.

Signed-off-by: Huan Yang <link at vivo.com>
---
 drivers/dma-buf/udmabuf.c | 65 ++++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 32 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index 4ec54c60d76c..8f9cb0e2e71a 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -296,12 +296,12 @@ 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;
+	pgoff_t upgcnt = 0, pglimit, pgbuf = 0;
+	long ret = -EINVAL;
 	struct file *memfd = NULL;
 	struct folio **folios;
 	struct udmabuf *ubuf;
-	u32 i, j, k, flags;
+	u32 i, flags;
 	loff_t end;
 
 	ubuf = kzalloc(sizeof(*ubuf), GFP_KERNEL);
@@ -315,22 +315,21 @@ static long udmabuf_create(struct miscdevice *device,
 			goto err;
 		if (!IS_ALIGNED(list[i].size, PAGE_SIZE))
 			goto err;
-		ubuf->pagecount += list[i].size >> PAGE_SHIFT;
+		upgcnt += list[i].size >> PAGE_SHIFT;
 		if (ubuf->pagecount > pglimit)
 			goto err;
 	}
 
-	if (!ubuf->pagecount)
+	if (!upgcnt)
 		goto err;
 
-	ubuf->folios = kvmalloc_array(ubuf->pagecount, sizeof(*ubuf->folios),
+	ubuf->folios = kvmalloc_array(upgcnt, 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(upgcnt, sizeof(*ubuf->offsets), GFP_KERNEL);
 	if (!ubuf->offsets) {
 		ret = -ENOMEM;
 		goto err;
@@ -338,6 +337,10 @@ static long udmabuf_create(struct miscdevice *device,
 
 	pgbuf = 0;
 	for (i = 0; i < head->count; i++) {
+		pgoff_t pgoff, pgcnt;
+		u32 j, cnt;
+		long nr_folios;
+
 		memfd = fget(list[i].memfd);
 		ret = check_memfd_seals(memfd);
 		if (ret < 0)
@@ -351,38 +354,36 @@ static long udmabuf_create(struct miscdevice *device,
 		}
 
 		end = list[i].offset + (pgcnt << PAGE_SHIFT) - 1;
-		ret = memfd_pin_folios(memfd, list[i].offset, end,
-				       folios, pgcnt, &pgoff);
-		if (ret <= 0) {
+		nr_folios = memfd_pin_folios(memfd, list[i].offset, end, folios,
+					     pgcnt, &pgoff);
+		if (nr_folios <= 0) {
 			kvfree(folios);
-			if (!ret)
-				ret = -EINVAL;
+			ret = nr_folios ? nr_folios : -EINVAL;
 			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;
-				}
+		for (j = 0, cnt = 0; j < nr_folios; ++j, pgoff = 0) {
+			u32 k;
+			long fsize = folio_size(folios[j]);
+
+			ret = add_to_unpin_list(&ubuf->unpin_list, folios[j]);
+			if (ret < 0) {
+				kfree(folios);
+				goto err;
 			}
 
-			pgbuf++;
-			if (++pgoff == folio_nr_pages(folios[k])) {
-				pgoff = 0;
-				if (++k == nr_folios)
-					break;
+			for (k = pgoff; k < fsize; k += PAGE_SIZE) {
+				ubuf->folios[pgbuf] = folios[j];
+				ubuf->offsets[pgbuf] = k;
+				++pgbuf;
+
+				if (++cnt >= pgcnt)
+					goto end;
 			}
 		}
-
+end:
+		// update the number of pages that have already been set up.
+		ubuf->pagecount += pgcnt;
 		kvfree(folios);
 		fput(memfd);
 		memfd = NULL;
-- 
2.45.2