ext4: fix wrong size computation in ext4_mb_normalize_request()

As the member fe_len defined in struct ext4_free_extent is expressed as
number of clusters, the variable "size" computation is wrong, we need to
first translate fe_len to block number, then to bytes.
Signed-off-by: NXiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NLukas Czerner <lczerner@redhat.com>

fs/ext4/mballoc.c

@@ -3075,8 +3075,9 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
 							(23 - bsbits)) << 23;
 		size = 8 * 1024 * 1024;
 	} else {
-		start_off = (loff_t)ac->ac_o_ex.fe_logical << bsbits;
-		size	  = ac->ac_o_ex.fe_len << bsbits;
+		start_off = (loff_t) ac->ac_o_ex.fe_logical << bsbits;
+		size	  = (loff_t) EXT4_C2B(EXT4_SB(ac->ac_sb),
+					      ac->ac_o_ex.fe_len) << bsbits;
 	}
 	size = size >> bsbits;
 	start = start_off >> bsbits;