This patches introduce bio_for_each_segment_all_sp() and
bio_for_each_segment_all_mp().
bio_for_each_segment_all_sp() is for replacing bio_for_each_segment_all()
in case that the returned bvec has to be single page bvec.
bio_for_each_segment_all_mp() is for replacing bio_for_each_segment_all()
in case that user wants to update the returned bvec via the pointer.
Signed-off-by: Ming Lei <ming....@redhat.com>
---
include/linux/bio.h | 24 ++++++++++++++++++++++++
include/linux/blk_types.h | 6 ++++++
2 files changed, 30 insertions(+)
diff --git a/include/linux/bio.h b/include/linux/bio.h
index ac8248558ab4..cd43b4b80472 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -232,6 +232,30 @@ static inline bool bio_rewind_iter(struct bio *bio, struct
bvec_iter *iter,
#define bio_for_each_segment_mp(bvl, bio, iter)
\
__bio_for_each_segment_mp(bvl, bio, iter, (bio)->bi_iter)
+/*
+ * This helper returns each bvec stored in bvec table directly,
+ * so the returned bvec points to one multipage bvec in the table
+ * and caller can update the bvec via the returnd pointer.
+ */
+#define bio_for_each_segment_all_mp(bvl, bio, i) \
+ bio_for_each_segment_all((bvl), (bio), (i))
+
+/*
+ * This helper returns singlepage bvec to caller, and the sp bvec
+ * is generated in-flight from multipage bvec stored in bvec table.
+ * So we can _not_ change the bvec stored in bio->bi_io_vec[] via
+ * this helper.
+ *
+ * If someone need to update bvec in the table, please use
+ * bio_for_each_segment_all_mp() and make sure it is correctly used
+ * since the bvec points to one multipage bvec.
+ */
+#define bio_for_each_segment_all_sp(bvl, bio, i, bi) \
+ for ((bi).iter = BVEC_ITER_ALL_INIT, i = 0, bvl = &(bi).bv; \
+ (bi).iter.bi_idx < (bio)->bi_vcnt && \
+ (((bi).bv = bio_iter_iovec((bio), (bi).iter)), 1); \
+ bio_advance_iter((bio), &(bi).iter, (bi).bv.bv_len), i++)
+
#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/blk_types.h b/include/linux/blk_types.h
index d2eb87c84d82..99b47b7204fe 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -119,6 +119,12 @@ struct bio {
#define BIO_RESET_BYTES offsetof(struct bio, bi_max_vecs)
+/* this iter is only for implementing bio_for_each_segment_rd() */
+struct bvec_iter_all {
+ struct bvec_iter iter;
+ struct bio_vec bv; /* in-flight singlepage bvec */
+};
+
/*
* bio flags
*/
--
2.9.4
