[PATCH 01/27] block: bio: introduce 4 helpers for cleanup

[Ming Lei]

Some drivers access bio->bi_vcnt and bio->bi_io_vec directly,
firstly it isn't a good practice, secondly it may cause trouble
for converting to multipage bvecs.

So this patches introduces 4 helpers for cleaning up this kind
of usage.

Both bio_pages() and bio_is_full() can be convertd to support
multipage bvecs easily.

For bio_get_base_vec() and bio_set_vec_table(), they are often
used during initializing a new bio or in case of single bvec
bio. With the two new helpers, it becomes easy to audit access
of .bi_io_vec and .bi_vcnt.

Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
---
 include/linux/bio.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 88bc64f..2179bc4 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -310,6 +310,34 @@ static inline void bio_clear_flag(struct bio *bio, unsigned int bit)
 	bio->bi_flags &= ~(1U << bit);
 }
 
+static inline bool bio_is_full(struct bio *bio)
+{
+	WARN_ONCE(bio_flagged(bio, BIO_CLONED), "cloned bio");
+
+	return bio->bi_vcnt >= bio->bi_max_vecs;
+}
+
+static inline struct bio_vec *bio_get_base_vec(struct bio *bio)
+{
+	return __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
+}
+
+/* This helper should be used for setting bvec table on a new bio */
+static inline void bio_set_vec_table(struct bio *bio, struct bio_vec *table,
+			      unsigned max_vecs)
+{
+	bio->bi_io_vec = table;
+	bio->bi_max_vecs = max_vecs;
+}
+
+/* For singlepage bvecs, one segment includes one page */
+static inline unsigned bio_pages(struct bio *bio)
+{
+	if (!bio_flagged(bio, BIO_CLONED))
+		return bio->bi_vcnt;
+	return bio_segments(bio);
+}
+
 static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
 {
 	*bv = bio_iovec(bio);
-- 
1.9.1