ext4: factor out a io_submit_need_new_bio helper

Factor out a helper to prepare for making this logic a bit more
complex in the next commit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20260302141922.370070-4-hch@lst.de
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

Author: Christoph Hellwig

fs/ext4/page-io.c

@@ -439,14 +439,23 @@ static void io_submit_init_bio(struct ext4_io_submit *io,
 	wbc_init_bio(io->io_wbc, bio);
 }
 
+static bool io_submit_need_new_bio(struct ext4_io_submit *io,
+				   struct buffer_head *bh)
+{
+	if (bh->b_blocknr != io->io_next_block)
+		return true;
+	if (!fscrypt_mergeable_bio_bh(io->io_bio, bh))
+		return true;
+	return false;
+}
+
 static void io_submit_add_bh(struct ext4_io_submit *io,
 			     struct inode *inode,
 			     struct folio *folio,
 			     struct folio *io_folio,
 			     struct buffer_head *bh)
 {
-	if (io->io_bio && (bh->b_blocknr != io->io_next_block ||
-			   !fscrypt_mergeable_bio_bh(io->io_bio, bh))) {
+	if (io->io_bio && io_submit_need_new_bio(io, bh)) {
 submit_and_retry:
 		ext4_io_submit(io);
 	}