[PATCH 2/5] block: add a bio_chain_and_submit helper

[Christoph Hellwig <hch@lst.de>]

This is basically blk_next_bio just with the bio allocation moved
to the caller to allow for more flexible bio handling in the caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/bio.c         | 28 ++++++++++++++++++++--------
 include/linux/bio.h |  1 +
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index d24420ed1c4c6f..32ff538b29e564 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -345,18 +345,30 @@ void bio_chain(struct bio *bio, struct bio *parent)
 }
 EXPORT_SYMBOL(bio_chain);
 
-struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
-		unsigned int nr_pages, blk_opf_t opf, gfp_t gfp)
+/**
+ * bio_chain_and_submit - submit a bio after chaining it to another one
+ * @prev: bio to chain and submit
+ * @new: bio to chain to
+ *
+ * If @prev is non-NULL, chain it to @new and submit it.
+ *
+ * Return: @new.
+ */
+struct bio *bio_chain_and_submit(struct bio *prev, struct bio *new)
 {
-	struct bio *new = bio_alloc(bdev, nr_pages, opf, gfp);
-
-	if (bio) {
-		bio_chain(bio, new);
-		submit_bio(bio);
+	if (prev) {
+		bio_chain(prev, new);
+		submit_bio(prev);
 	}
-
 	return new;
 }
+EXPORT_SYMBOL_GPL(bio_chain_and_submit);
+
+struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
+		unsigned int nr_pages, blk_opf_t opf, gfp_t gfp)
+{
+	return bio_chain_and_submit(bio, bio_alloc(bdev, nr_pages, opf, gfp));
+}
 EXPORT_SYMBOL_GPL(blk_next_bio);
 
 static void bio_alloc_rescue(struct work_struct *work)
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 875d792bffff82..643d61b7cb82f7 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -824,5 +824,6 @@ static inline void bio_clear_polled(struct bio *bio)
 
 struct bio *blk_next_bio(struct bio *bio, struct block_device *bdev,
 		unsigned int nr_pages, blk_opf_t opf, gfp_t gfp);
+struct bio *bio_chain_and_submit(struct bio *prev, struct bio *new);
 
 #endif /* __LINUX_BIO_H */
-- 
2.39.2