btrfs: don't take a bio_counter reference for cloned bios

Stop grabbing an extra bio_counter reference for each clone bio in a
mirrored write and instead just release the one original reference in
btrfs_end_bioc once all the bios for a single btrfs_bio have completed
instead of at the end of btrfs_submit_bio once all bios have been
submitted.

This means the reference is now carried by the "upper" btrfs_bio only
instead of each lower bio.

Also remove the now unused btrfs_bio_counter_inc_noblocked helper.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -4076,7 +4076,6 @@ static inline void btrfs_init_full_stripe_locks_tree(
 
 /* dev-replace.c */
 void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info);
-void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info);
 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount);
 
 static inline void btrfs_bio_counter_dec(struct btrfs_fs_info *fs_info)

fs/btrfs/dev-replace.c

@@ -1283,11 +1283,6 @@ int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
 	return 1;
 }
 
-void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
-{
-	percpu_counter_inc(&fs_info->dev_replace.bio_counter);
-}
-
 void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
 {
 	percpu_counter_sub(&fs_info->dev_replace.bio_counter, amount);

fs/btrfs/volumes.c

@@ -6676,6 +6676,8 @@ static void btrfs_end_bioc(struct btrfs_io_context *bioc, bool async)
 	struct bio *orig_bio = bioc->orig_bio;
 	struct btrfs_bio *bbio = btrfs_bio(orig_bio);
 
+	btrfs_bio_counter_dec(bioc->fs_info);
+
 	bbio->mirror_num = bioc->mirror_num;
 	orig_bio->bi_private = bioc->private;
 	orig_bio->bi_end_io = bioc->end_io;
@@ -6723,7 +6725,6 @@ static void btrfs_end_bio(struct bio *bio)
 	if (bio != bioc->orig_bio)
 		bio_put(bio);
 
-	btrfs_bio_counter_dec(bioc->fs_info);
 	if (atomic_dec_and_test(&bioc->stripes_pending))
 		btrfs_end_bioc(bioc, true);
 }
@@ -6778,8 +6779,6 @@ static void submit_stripe_bio(struct btrfs_io_context *bioc,
 		(unsigned long)dev->bdev->bd_dev, rcu_str_deref(dev->name),
 		dev->devid, bio->bi_iter.bi_size);
 
-	btrfs_bio_counter_inc_noblocked(fs_info);
-
 	btrfsic_check_bio(bio);
 	submit_bio(bio);
 }
@@ -6831,7 +6830,6 @@ void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror
 
 		submit_stripe_bio(bioc, bio, dev_nr, should_clone);
 	}
-	btrfs_bio_counter_dec(fs_info);
 }
 
 static bool dev_args_match_fs_devices(const struct btrfs_dev_lookup_args *args,