block: use FIELD_SIZEOF to calculate size of a field

use FIELD_SIZEOF instead of open coding

Signed-off-by: Maninder Singh <maninder1.s@samsung.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-core.c b/block/blk-core.c
index 82819e6..627ed0c 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3370,7 +3370,7 @@ EXPORT_SYMBOL(blk_post_runtime_resume);
 int __init blk_dev_init(void)
 {
        BUILD_BUG_ON(__REQ_NR_BITS > 8 *
-                       sizeof(((struct request *)0)->cmd_flags));
+                       FIELD_SIZEOF(struct request, cmd_flags));
 
        /* used for unplugging and affects IO latency/throughput - HIGHPRI */
        kblockd_workqueue = alloc_workqueue("kblockd",