btrfs: properly abstract the parity raid bio handling

The parity raid write/recover functionality is currently not very well
abstracted from the bio submission and completion handling in volumes.c:

 - the raid56 code directly completes the original btrfs_bio fed into
   btrfs_submit_bio instead of dispatching back to volumes.c
 - the raid56 code consumes the bioc and bio_counter references taken
   by volumes.c, which also leads to special casing of the calls from
   the scrub code into the raid56 code

To fix this up supply a bi_end_io handler that calls back into the
volumes.c machinery, which then puts the bioc, decrements the bio_counter
and completes the original bio, and updates the scrub code to also
take ownership of the bioc and bio_counter in all cases.

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

1 files changed, 17 insertions, 1 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 44c7529c70c3..112547d6d5d4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6684,6 +6684,20 @@ static void btrfs_end_bio_work(struct work_struct *work)
 	bio_endio(&bbio->bio);
 }
 
+static void btrfs_raid56_end_io(struct bio *bio)
+{
+	struct btrfs_io_context *bioc = bio->bi_private;
+	struct btrfs_bio *bbio = btrfs_bio(bio);
+
+	btrfs_bio_counter_dec(bioc->fs_info);
+	bbio->mirror_num = bioc->mirror_num;
+	bio->bi_end_io = bioc->end_io;
+	bio->bi_private = bioc->private;
+	bio->bi_end_io(bio);
+
+	btrfs_put_bioc(bioc);
+}
+
 static void btrfs_end_bio(struct bio *bio)
 {
 	struct btrfs_io_stripe *stripe = bio->bi_private;
@@ -6817,10 +6831,12 @@ void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror
 
 	if ((bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) &&
 	    ((btrfs_op(bio) == BTRFS_MAP_WRITE) || (mirror_num > 1))) {
+		bio->bi_private = bioc;
+		bio->bi_end_io = btrfs_raid56_end_io;
 		if (btrfs_op(bio) == BTRFS_MAP_WRITE)
 			raid56_parity_write(bio, bioc);
 		else
-			raid56_parity_recover(bio, bioc, mirror_num, true);
+			raid56_parity_recover(bio, bioc, mirror_num);
 		return;
 	}