On Sun, Feb 26, 2017 at 2:22 AM, Christoph Hellwig [off-list ref] wrote:

quoted

+static inline unsigned bio_segments_all(struct bio *bio)
+{
+     WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED));
+
+     return bio->bi_vcnt;
+}

I don't think this helpers really adds any benefit.

IMO the first benefit is that misusing of .bi_vcnt can be warned, and
another one is that we have to introduce this helper if multipage bvec
is supported.

Thanks,
Ming Lei