[PATCH 01/10] btrfs: Always initialize btrfs_bio::tgtdev_map/raid_map pointers

[Nikolay Borisov <nborisov@suse.com>]

Since btrfs_bio always contains the extra space for the tgtdev_map and
raid_maps it's pointless to make the assignment iff specific conditions
are met. Instead, always assign the pointers to their correct value at
allocation time. To accommodate this change also move code a bit in
__btrfs_map_block so that btrfs_bio::stripes array is always initialized
before the raid_map, subsequently move the call to sort_parity_stripes
in the 'if' building the raid_map, retaining the old behavior.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/volumes.c | 34 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index cb9883c7f8b7..d74d21af77fb 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5522,6 +5522,9 @@ static struct btrfs_bio *alloc_btrfs_bio(int total_stripes, int real_stripes)
 	atomic_set(&bbio->error, 0);
 	refcount_set(&bbio->refs, 1);
 
+	bbio->tgtdev_map = (int *)(bbio->stripes + total_stripes);
+	bbio->raid_map = (u64 *)(bbio->tgtdev_map + real_stripes);
+
 	return bbio;
 }
 
@@ -6144,8 +6147,16 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 		ret = -ENOMEM;
 		goto out;
 	}
-	if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL)
-		bbio->tgtdev_map = (int *)(bbio->stripes + num_alloc_stripes);
+
+	for (i = 0; i < num_stripes; i++) {
+		bbio->stripes[i].physical =
+			map->stripes[stripe_index].physical +
+			stripe_offset +
+			stripe_nr * map->stripe_len;
+		bbio->stripes[i].dev =
+			map->stripes[stripe_index].dev;
+		stripe_index++;
+	}
 
 	/* build raid_map */
 	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK && need_raid_map &&
@@ -6153,10 +6164,6 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 		u64 tmp;
 		unsigned rot;
 
-		bbio->raid_map = (u64 *)((void *)bbio->stripes +
-				 sizeof(struct btrfs_bio_stripe) *
-				 num_alloc_stripes +
-				 sizeof(int) * tgtdev_indexes);
 
 		/* Work out the disk rotation on this stripe-set */
 		div_u64_rem(stripe_nr, num_stripes, &rot);
@@ -6171,25 +6178,14 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
 		if (map->type & BTRFS_BLOCK_GROUP_RAID6)
 			bbio->raid_map[(i+rot+1) % num_stripes] =
 				RAID6_Q_STRIPE;
-	}
-
 
-	for (i = 0; i < num_stripes; i++) {
-		bbio->stripes[i].physical =
-			map->stripes[stripe_index].physical +
-			stripe_offset +
-			stripe_nr * map->stripe_len;
-		bbio->stripes[i].dev =
-			map->stripes[stripe_index].dev;
-		stripe_index++;
+		sort_parity_stripes(bbio, num_stripes);
 	}
 
+
 	if (need_full_stripe(op))
 		max_errors = btrfs_chunk_max_errors(map);
 
-	if (bbio->raid_map)
-		sort_parity_stripes(bbio, num_stripes);
-
 	if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL &&
 	    need_full_stripe(op)) {
 		handle_ops_on_dev_replace(op, &bbio, dev_replace, &num_stripes,
-- 
2.17.1