btrfs: read stripe len directly in btrfs_rmap_block

extent_map::orig_block_len contains the size of a physical stripe when
it's used to describe block groups (calculated in read_one_chunk via
calc_stripe_length or calculated in decide_stripe_size and then assigned
to extent_map::orig_block_len in create_chunk). Exploit this fact to get
the size directly rather than opencoding the calculations. No functional
changes.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index c037ef5..956ae62 100644 (file)
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1657,19 +1657,12 @@ int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
                return -EIO;
 
        map = em->map_lookup;
-       data_stripe_length = em->len;
+       data_stripe_length = em->orig_block_len;
        io_stripe_size = map->stripe_len;
 
-       if (map->type & BTRFS_BLOCK_GROUP_RAID10)
-               data_stripe_length = div_u64(data_stripe_length,
-                                            map->num_stripes / map->sub_stripes);
-       else if (map->type & BTRFS_BLOCK_GROUP_RAID0)
-               data_stripe_length = div_u64(data_stripe_length, map->num_stripes);
-       else if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
-               data_stripe_length = div_u64(data_stripe_length,
-                                            nr_data_stripes(map));
+       /* For RAID5/6 adjust to a full IO stripe length */
+       if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
                io_stripe_size = map->stripe_len * nr_data_stripes(map);
-       }
 
        buf = kcalloc(map->num_stripes, sizeof(u64), GFP_NOFS);
        if (!buf) {