block: shrink rq_map_data a bit

We don't need full ints for several of these members. Change the
page_order and nr_entries to unsigned shorts, and the true/false from_user
and null_mapped to booleans.

This shrinks the struct from 32 to 24 bytes on 64-bit archs.

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-map.c b/block/blk-map.c
index 7196a6b..379c52d 100644 (file)
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -158,7 +158,7 @@ static int bio_copy_user_iov(struct request *rq, struct rq_map_data *map_data,
        bio_init(bio, NULL, bio->bi_inline_vecs, nr_pages, req_op(rq));
 
        if (map_data) {
-               nr_pages = 1 << map_data->page_order;
+               nr_pages = 1U << map_data->page_order;
                i = map_data->offset / PAGE_SIZE;
        }
        while (len) {

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index c385752..74b99d7 100644 (file)
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -963,11 +963,11 @@ blk_status_t blk_insert_cloned_request(struct request *rq);
 
 struct rq_map_data {
        struct page **pages;
-       int page_order;
-       int nr_entries;
        unsigned long offset;
-       int null_mapped;
-       int from_user;
+       unsigned short page_order;
+       unsigned short nr_entries;
+       bool null_mapped;
+       bool from_user;
 };
 
 int blk_rq_map_user(struct request_queue *, struct request *,