Re: [PATCH 4/4] block: add large command support

[Jens Axboe <jens.axboe@oracle.com>]

On Mon, Apr 14 2008, FUJITA Tomonori wrote:
> 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>
> ---
>  block/blk-core.c       |    1 +
>  drivers/ide/ide-io.c   |    1 +
>  include/linux/blkdev.h |   12 ++++++++++--
>  3 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 6669238..6f0968f 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -132,6 +132,7 @@ void rq_init(struct request_queue *q, struct request *rq)
>  	rq->errors = 0;
>  	rq->ref_count = 1;
>  	rq->cmd_len = 0;
> +	rq->cmd = rq->__cmd;
>  	memset(rq->cmd, 0, BLK_MAX_CDB);
>  	rq->data_len = 0;
>  	rq->extra_len = 0;
> diff --git a/drivers/ide/ide-io.c b/drivers/ide/ide-io.c
> index 7153796..bac5ea1 100644
> --- a/drivers/ide/ide-io.c
> +++ b/drivers/ide/ide-io.c
> @@ -1595,6 +1595,7 @@ void ide_init_drive_cmd (struct request *rq)
>  {
>  	memset(rq, 0, sizeof(*rq));
>  	rq->ref_count = 1;
> +	rq->cmd = rq->__cmd;
>  }
>  
>  EXPORT_SYMBOL(ide_init_drive_cmd);
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index b3a58ad..5710ae4 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 */
> @@ -812,6 +813,13 @@ static inline void put_dev_sector(Sector p)
>  	page_cache_release(p.v);
>  }
>  
> +static inline void rq_set_cmd(struct request *rq, unsigned char *cmd,
> +			      unsigned short cmd_len)
> +{
> +	rq->cmd = cmd;
> +	rq->cmd_len = cmd_len;
> +}
> +

This is 100% identical to what I suggested be done instead, so of course
I agree with this.

-- 
Jens Axboe