[PATCH v2 1/3] block: bio: kill BIO_SEG_VALID flag

[Johannes Thumshirn <jthumshirn@suse.de>]

From: Jens Axboe <axboe@kernel.dk>

Kill the BIO_SEG_VALID flag. We should just use ->bi_phys_segments to tell
if it's valid or not.

This patch uses -1 to signify it's not.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
[ jth initialize pc bios with 1 phys segment and WARN if we're submitting
bios with -1 segments ]
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 block/bio.c               | 15 +++++++++------
 block/blk-core.c          |  1 +
 block/blk-merge.c         | 13 ++++++-------
 drivers/md/raid5.c        |  2 +-
 include/linux/blk_types.h |  1 -
 5 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 71a78d9fb8b7..a79b2bbcffd0 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -280,6 +280,7 @@ void bio_init(struct bio *bio, struct bio_vec *table,
 	      unsigned short max_vecs)
 {
 	memset(bio, 0, sizeof(*bio));
+	bio->bi_phys_segments = -1;
 	atomic_set(&bio->__bi_remaining, 1);
 	atomic_set(&bio->__bi_cnt, 1);
 
@@ -305,6 +306,7 @@ void bio_reset(struct bio *bio)
 	bio_uninit(bio);
 
 	memset(bio, 0, BIO_RESET_BYTES);
+	bio->bi_phys_segments = -1;
 	bio->bi_flags = flags;
 	atomic_set(&bio->__bi_remaining, 1);
 }
@@ -573,7 +575,7 @@ EXPORT_SYMBOL(bio_put);
 
 int bio_phys_segments(struct request_queue *q, struct bio *bio)
 {
-	if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+	if (unlikely(bio->bi_phys_segments == -1))
 		blk_recount_segments(q, bio);
 
 	return bio->bi_phys_segments;
@@ -712,7 +714,10 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
 	bvec->bv_len = len;
 	bvec->bv_offset = offset;
 	bio->bi_vcnt++;
-	bio->bi_phys_segments++;
+	if (bio->bi_phys_segments == -1)
+		bio->bi_phys_segments = 1;
+	else
+		bio->bi_phys_segments++;
 	bio->bi_iter.bi_size += len;
 
 	/*
@@ -731,7 +736,7 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
 
 	/* If we may be able to merge these biovecs, force a recount */
 	if (bio->bi_vcnt > 1 && biovec_phys_mergeable(q, bvec - 1, bvec))
-		bio_clear_flag(bio, BIO_SEG_VALID);
+		bio->bi_phys_segments = -1;
 
  done:
 	return len;
@@ -1913,10 +1918,8 @@ void bio_trim(struct bio *bio, int offset, int size)
 	if (offset == 0 && size == bio->bi_iter.bi_size)
 		return;
 
-	bio_clear_flag(bio, BIO_SEG_VALID);
-
+	bio->bi_phys_segments = -1;
 	bio_advance(bio, offset << 9);
-
 	bio->bi_iter.bi_size = size;
 
 	if (bio_integrity(bio))
diff --git a/block/blk-core.c b/block/blk-core.c
index 4673ebe42255..53372a16dd7c 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1514,6 +1514,7 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
 	else if (bio_op(bio) == REQ_OP_DISCARD)
 		rq->nr_phys_segments = 1;
 
+	WARN_ON(rq->nr_phys_segments == -1);
 	rq->__data_len = bio->bi_iter.bi_size;
 	rq->bio = rq->biotail = bio;
 
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 1c9d4f0f96ea..16c2ae69c46b 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -343,7 +343,6 @@ void blk_queue_split(struct request_queue *q, struct bio **bio)
 	/* physical segments can be figured out during splitting */
 	res = split ? split : *bio;
 	res->bi_phys_segments = nsegs;
-	bio_set_flag(res, BIO_SEG_VALID);
 
 	if (split) {
 		/* there isn't chance to merge the splitted bio */
@@ -440,8 +439,6 @@ void blk_recount_segments(struct request_queue *q, struct bio *bio)
 	bio->bi_next = NULL;
 	bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
 	bio->bi_next = nxt;
-
-	bio_set_flag(bio, BIO_SEG_VALID);
 }
 
 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
@@ -620,6 +617,8 @@ static inline int ll_new_hw_segment(struct request_queue *q,
 {
 	int nr_phys_segs = bio_phys_segments(q, bio);
 
+	if (WARN_ON(nr_phys_segs == -1))
+		nr_phys_segs = 0;
 	if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
 		goto no_merge;
 
@@ -651,9 +650,9 @@ int ll_back_merge_fn(struct request_queue *q, struct request *req,
 		req_set_nomerge(q, req);
 		return 0;
 	}
-	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
+	if (req->biotail->bi_phys_segments == -1)
 		blk_recount_segments(q, req->biotail);
-	if (!bio_flagged(bio, BIO_SEG_VALID))
+	if (bio->bi_phys_segments == -1)
 		blk_recount_segments(q, bio);
 
 	return ll_new_hw_segment(q, req, bio);
@@ -673,9 +672,9 @@ int ll_front_merge_fn(struct request_queue *q, struct request *req,
 		req_set_nomerge(q, req);
 		return 0;
 	}
-	if (!bio_flagged(bio, BIO_SEG_VALID))
+	if (bio->bi_phys_segments == -1)
 		blk_recount_segments(q, bio);
-	if (!bio_flagged(req->bio, BIO_SEG_VALID))
+	if (req->bio->bi_phys_segments == -1)
 		blk_recount_segments(q, req->bio);
 
 	return ll_new_hw_segment(q, req, bio);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index c033bfcb209e..79eb54dcf0f9 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5247,7 +5247,7 @@ static int raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio)
 		rcu_read_unlock();
 		raid_bio->bi_next = (void*)rdev;
 		bio_set_dev(align_bi, rdev->bdev);
-		bio_clear_flag(align_bi, BIO_SEG_VALID);
+		align_bi->bi_phys_segments = -1;
 
 		if (is_badblock(rdev, align_bi->bi_iter.bi_sector,
 				bio_sectors(align_bi),
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index d66bf5f32610..472059e92071 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -215,7 +215,6 @@ struct bio {
 /*
  * bio flags
  */
-#define BIO_SEG_VALID	1	/* bi_phys_segments valid */
 #define BIO_CLONED	2	/* doesn't own data */
 #define BIO_BOUNCED	3	/* bio is a bounce bio */
 #define BIO_USER_MAPPED 4	/* contains user pages */
-- 
2.16.4