[Devel] [PATCH RHEL8 COMMIT] block: introduce bio_for_each_bvec() and rq_for_each_bvec()

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-240.1.1.vz8.5.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-240.1.1.vz8.5.30
------>
commit a721b02942d604b3027881c2adebc64d2e8d0dd6
Author: Ming Lei <ming.lei at redhat.com>
Date:   Mon May 17 19:05:02 2021 +0300

    block: introduce bio_for_each_bvec() and rq_for_each_bvec()
    
    ms commit d18d91740ad2
    
    bio_for_each_bvec() is used for iterating over multi-page bvec for bio
    split & merge code.
    
    rq_for_each_bvec() can be used for drivers which may handle the
    multi-page bvec directly, so far loop is one perfect use case.
    
    Reviewed-by: Christoph Hellwig <hch at lst.de>
    Reviewed-by: Omar Sandoval <osandov at fb.com>
    Signed-off-by: Ming Lei <ming.lei at redhat.com>
    Signed-off-by: Jens Axboe <axboe at kernel.dk>
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    
    =====================
    Patchset description:
    
    dm-ploop: Kill loop
    
    Intermediate patches can't be base for bisect.
    
    In scope of https://jira.sw.ru/browse/PSBM-123654
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 include/linux/bio.h    | 10 ++++++++++
 include/linux/blkdev.h |  4 ++++
 2 files changed, 14 insertions(+)

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 32870a11c560..ae7fc1992779 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -156,6 +156,16 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
 #define bio_for_each_segment(bvl, bio, iter)				\
 	__bio_for_each_segment(bvl, bio, iter, (bio)->bi_iter)
 
+#define __bio_for_each_bvec(bvl, bio, iter, start)		\
+	for (iter = (start);						\
+	     (iter).bi_size &&						\
+		((bvl = mp_bvec_iter_bvec((bio)->bi_io_vec, (iter))), 1); \
+	     bio_advance_iter((bio), &(iter), (bvl).bv_len))
+
+/* iterate over multi-page bvec */
+#define bio_for_each_bvec(bvl, bio, iter)			\
+	__bio_for_each_bvec(bvl, bio, iter, (bio)->bi_iter)
+
 #define bio_iter_last(bvec, iter) ((iter).bi_size == (bvec).bv_len)
 
 static inline unsigned bio_segments(struct bio *bio)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 248b66114415..8f8161d0477f 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -862,6 +862,10 @@ struct req_iterator {
 	__rq_for_each_bio(_iter.bio, _rq)			\
 		bio_for_each_segment(bvl, _iter.bio, _iter.iter)
 
+#define rq_for_each_bvec(bvl, _rq, _iter)			\
+	__rq_for_each_bio(_iter.bio, _rq)			\
+		bio_for_each_bvec(bvl, _iter.bio, _iter.iter)
+
 #define rq_iter_last(bvec, _iter)				\
 		(_iter.bio->bi_next == NULL &&			\
 		 bio_iter_last(bvec, _iter.iter))