block: add large command support

This patch changes rq->cmd from the static array to a pointer to
support large commands.

We rarely handle large commands. So for optimization, a struct request
still has a static array for a command. rq_init sets rq->cmd pointer
to the static array.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

2 files changed, 4 insertions, 2 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index e6fdb288be65..5d09f8c56024 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -117,6 +117,7 @@ void blk_rq_init(struct request_queue *q, struct request *rq)
         rq->sector = rq->hard_sector = (sector_t) -1;
         INIT_HLIST_NODE(&rq->hash);
         RB_CLEAR_NODE(&rq->rb_node);
+        rq->cmd = rq->__cmd;
         rq->tag = -1;
         rq->ref_count = 1;
 }
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d17032c347c0..08df1ea8bac4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -215,8 +215,9 @@ struct request {
         /*
          * when request is used as a packet command carrier
          */
-        unsigned int cmd_len;
-        unsigned char cmd[BLK_MAX_CDB];
+        unsigned short cmd_len;
+        unsigned char __cmd[BLK_MAX_CDB];
+        unsigned char *cmd;
 
         unsigned int data_len;
         unsigned int extra_len; /* length of alignment and padding */