btrfs: replace s_blocksize_bits with fs_info::sectorsize_bits

The value of super_block::s_blocksize_bits is the same as
fs_info::sectorsize_bits, but we don't need to do the extra dereferences
in many functions and storing the bits as u32 (in fs_info) generates
shorter assembly.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 2bfad19..b94b4fe 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1410,7 +1410,7 @@ struct btrfs_map_token {
 };
 
 #define BTRFS_BYTES_TO_BLKS(fs_info, bytes) \
-				((bytes) >> (fs_info)->sb->s_blocksize_bits)
+				((bytes) >> (fs_info)->sectorsize_bits)
 
 static inline void btrfs_init_map_token(struct btrfs_map_token *token,
 					struct extent_buffer *eb)