[PATCH] block: remove dead queue_dma_alignment branch from bio_map_user_iov()

[PATCH] block: remove dead queue_dma_alignment branch from bio_map_user_iov()

[Lukas Bulwahn]

If queue_dma_alignment(rq->q), then blk_rq_map_user_iov() will call
bio_copy_user_iov() and not bio_map_user_iov(). So, bio_map_user_iov() does
not need to handle the queue_dma_alignment(rq->q) case in any special way.

Remove this dead branch from bio_map_user_iov().

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
---
 block/blk-map.c | 41 ++++++++++++++++++-----------------------
 1 file changed, 18 insertions(+), 23 deletions(-)

diff --git a/block/blk-map.c b/block/blk-map.c
index 4526adde0156..1cccdb776905 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -260,31 +260,26 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
 
 		npages = DIV_ROUND_UP(offs + bytes, PAGE_SIZE);
 
-		if (unlikely(offs & queue_dma_alignment(rq->q))) {
-			ret = -EINVAL;
-			j = 0;
-		} else {
-			for (j = 0; j < npages; j++) {
-				struct page *page = pages[j];
-				unsigned int n = PAGE_SIZE - offs;
-				bool same_page = false;
-
-				if (n > bytes)
-					n = bytes;
-
-				if (!bio_add_hw_page(rq->q, bio, page, n, offs,
-						     max_sectors, &same_page)) {
-					if (same_page)
-						put_page(page);
-					break;
-				}
-
-				added += n;
-				bytes -= n;
-				offs = 0;
+		for (j = 0; j < npages; j++) {
+			struct page *page = pages[j];
+			unsigned int n = PAGE_SIZE - offs;
+			bool same_page = false;
+
+			if (n > bytes)
+				n = bytes;
+
+			if (!bio_add_hw_page(rq->q, bio, page, n, offs,
+					     max_sectors, &same_page)) {
+				if (same_page)
+					put_page(page);
+				break;
 			}
-			iov_iter_advance(iter, added);
+
+			added += n;
+			bytes -= n;
+			offs = 0;
 		}
+		iov_iter_advance(iter, added);
 		/*
 		 * release the pages we didn't map into the bio, if any
 		 */
-- 
2.17.1

Re: [PATCH] block: remove dead queue_dma_alignment branch from bio_map_user_iov()

[Christoph Hellwig]

On Tue, Jan 04, 2022 at 01:01:58PM +0100, Lukas Bulwahn wrote:
> If queue_dma_alignment(rq->q), then blk_rq_map_user_iov() will call
> bio_copy_user_iov() and not bio_map_user_iov(). So, bio_map_user_iov() does
> not need to handle the queue_dma_alignment(rq->q) case in any special way.
> 
> Remove this dead branch from bio_map_user_iov().

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>