mpage: split submit_bio and bio end_io handler for reads and writes

Split the submit_bio() and bio end_io handler for reads and writes similar
to other aops.

This is a prep patch before we convert end_io handlers to use folios.

Link: https://lkml.kernel.org/r/20230411122920.30134-3-p.raghav@samsung.comSigned-off-by: Pankaj Raghav <p.raghav@samsung.com>
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Martin Brandenburg <martin@omnibond.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Marshall <hubcap@omnibond.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/mpage.c

@@ -43,23 +43,41 @@
  * status of that page is hard.  See end_buffer_async_read() for the details.
  * There is no point in duplicating all that complexity.
  */
-static void mpage_end_io(struct bio *bio)
+static void mpage_read_end_io(struct bio *bio)
 {
 	struct bio_vec *bv;
 	struct bvec_iter_all iter_all;
 
-	bio_for_each_segment_all(bv, bio, iter_all) {
-		struct page *page = bv->bv_page;
-		page_endio(page, bio_op(bio),
+	bio_for_each_segment_all(bv, bio, iter_all)
+		page_endio(bv->bv_page, REQ_OP_READ,
 			   blk_status_to_errno(bio->bi_status));
-	}
 
 	bio_put(bio);
 }
 
-static struct bio *mpage_bio_submit(struct bio *bio)
+static void mpage_write_end_io(struct bio *bio)
+{
+	struct bio_vec *bv;
+	struct bvec_iter_all iter_all;
+
+	bio_for_each_segment_all(bv, bio, iter_all)
+		page_endio(bv->bv_page, REQ_OP_WRITE,
+			   blk_status_to_errno(bio->bi_status));
+
+	bio_put(bio);
+}
+
+static struct bio *mpage_bio_submit_read(struct bio *bio)
+{
+	bio->bi_end_io = mpage_read_end_io;
+	guard_bio_eod(bio);
+	submit_bio(bio);
+	return NULL;
+}
+
+static struct bio *mpage_bio_submit_write(struct bio *bio)
 {
-	bio->bi_end_io = mpage_end_io;
+	bio->bi_end_io = mpage_write_end_io;
 	guard_bio_eod(bio);
 	submit_bio(bio);
 	return NULL;
@@ -265,7 +283,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 	 * This folio will go to BIO.  Do we need to send this BIO off first?
 	 */
 	if (args->bio && (args->last_block_in_bio != blocks[0] - 1))
-		args->bio = mpage_bio_submit(args->bio);
+		args->bio = mpage_bio_submit_read(args->bio);
 
 alloc_new:
 	if (args->bio == NULL) {
@@ -278,7 +296,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 
 	length = first_hole << blkbits;
 	if (!bio_add_folio(args->bio, folio, length, 0)) {
-		args->bio = mpage_bio_submit(args->bio);
+		args->bio = mpage_bio_submit_read(args->bio);
 		goto alloc_new;
 	}
 
@@ -286,7 +304,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 	nblocks = map_bh->b_size >> blkbits;
 	if ((buffer_boundary(map_bh) && relative_block == nblocks) ||
 	    (first_hole != blocks_per_page))
-		args->bio = mpage_bio_submit(args->bio);
+		args->bio = mpage_bio_submit_read(args->bio);
 	else
 		args->last_block_in_bio = blocks[blocks_per_page - 1];
 out:
@@ -294,7 +312,7 @@ static struct bio *do_mpage_readpage(struct mpage_readpage_args *args)
 
 confused:
 	if (args->bio)
-		args->bio = mpage_bio_submit(args->bio);
+		args->bio = mpage_bio_submit_read(args->bio);
 	if (!folio_test_uptodate(folio))
 		block_read_full_folio(folio, args->get_block);
 	else
@@ -356,7 +374,7 @@ void mpage_readahead(struct readahead_control *rac, get_block_t get_block)
 		args.bio = do_mpage_readpage(&args);
 	}
 	if (args.bio)
-		mpage_bio_submit(args.bio);
+		mpage_bio_submit_read(args.bio);
 }
 EXPORT_SYMBOL(mpage_readahead);
 
@@ -373,7 +391,7 @@ int mpage_read_folio(struct folio *folio, get_block_t get_block)
 
 	args.bio = do_mpage_readpage(&args);
 	if (args.bio)
-		mpage_bio_submit(args.bio);
+		mpage_bio_submit_read(args.bio);
 	return 0;
 }
 EXPORT_SYMBOL(mpage_read_folio);
@@ -577,7 +595,7 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
 	 * This page will go to BIO.  Do we need to send this BIO off first?
 	 */
 	if (bio && mpd->last_block_in_bio != blocks[0] - 1)
-		bio = mpage_bio_submit(bio);
+		bio = mpage_bio_submit_write(bio);
 
 alloc_new:
 	if (bio == NULL) {
@@ -596,7 +614,7 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
 	wbc_account_cgroup_owner(wbc, &folio->page, folio_size(folio));
 	length = first_unmapped << blkbits;
 	if (!bio_add_folio(bio, folio, length, 0)) {
-		bio = mpage_bio_submit(bio);
+		bio = mpage_bio_submit_write(bio);
 		goto alloc_new;
 	}
 
@@ -606,7 +624,7 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
 	folio_start_writeback(folio);
 	folio_unlock(folio);
 	if (boundary || (first_unmapped != blocks_per_page)) {
-		bio = mpage_bio_submit(bio);
+		bio = mpage_bio_submit_write(bio);
 		if (boundary_block) {
 			write_boundary_block(boundary_bdev,
 					boundary_block, 1 << blkbits);
@@ -618,7 +636,7 @@ static int __mpage_writepage(struct folio *folio, struct writeback_control *wbc,
 
 confused:
 	if (bio)
-		bio = mpage_bio_submit(bio);
+		bio = mpage_bio_submit_write(bio);
 
 	/*
 	 * The caller has a ref on the inode, so *mapping is stable
@@ -652,7 +670,7 @@ mpage_writepages(struct address_space *mapping,
 	blk_start_plug(&plug);
 	ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
 	if (mpd.bio)
-		mpage_bio_submit(mpd.bio);
+		mpage_bio_submit_write(mpd.bio);
 	blk_finish_plug(&plug);
 	return ret;
 }