On Tue, 2008-03-25 at 18:32 +0200, Boaz Harrosh wrote:
> - add varlen_cdb and varlen_cdb_len to hold a large user cdb
> if needed. They start as empty. Allocation of buffer must
> be done by user and held until request execution is done.
> - Since there can be either a fix_length command up to 16 bytes
> or a variable_length, larger then 16 bytes, commands but never
> both, we hold the two types in a union to save space. The
> presence of varlen_cdb_len and cmd_len==0 signals a varlen_cdb
> mode.
> - Please use added rq_{set,get}_varlen_cdb() to set every thing
> up in a way that will not confuse drivers that do not support
> varlen_cdb's.
> - Note that this patch does not add any size to struct request
> since the unsigned cmd_len is split here to 2 ushorts, which
> is more then enough.
My first observation is that the block stuff all looks a bit
misnamed ... it's not about variable length commands it's about getting
block to accept packet commands larger than BLK_MAX_CDB, be they SCSI
OSD commands or ATA taskfiles.
> Signed-off-by: Boaz Harrosh <bharrosh@xxxxxxxxxxx>
> ---
> block/blk-core.c | 2 ++
> include/linux/blkdev.h | 27 +++++++++++++++++++++++++--
> 2 files changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 2a438a9..70d32f7 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -141,6 +141,8 @@ void rq_init(struct request_queue *q, struct request *rq)
> rq->end_io = NULL;
> rq->end_io_data = NULL;
> rq->next_rq = NULL;
> + rq->varlen_cdb_len = 0;
> + rq->varlen_cdb = NULL;
possibly s/varlen/large/
> }
>
> static void req_bio_endio(struct request *rq, struct bio *bio,
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 6f79d40..f829571 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -213,8 +213,15 @@ 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 short varlen_cdb_len; /* length of varlen_cdb buffer */
> + union {
> + unsigned char cmd[BLK_MAX_CDB];
> + unsigned char *varlen_cdb;/* an optional variable-length cdb.
> + * points to a user buffer that must
> + * be valid until end of request
> + */
again s/varlen/large/
> + };
>
> unsigned int data_len;
> unsigned int extra_len; /* length of alignment and padding */
> @@ -484,6 +491,22 @@ enum {
> #define rq_is_sync(rq) (rq_data_dir((rq)) == READ || (rq)->cmd_flags & REQ_RW_SYNC)
> #define rq_is_meta(rq) ((rq)->cmd_flags & REQ_RW_META)
>
> +static inline void rq_set_varlen_cdb(struct request *rq, u8 *cdb, short cdb_len)
> +{
> + rq->cmd_len = 0; /* Make sure legacy drivers don't get confused */
> + rq->varlen_cdb_len = cdb_len;
> + rq->varlen_cdb = cdb;
> +}
> +
> +/* If ! a varlen_cdb than return NULL */
> +static inline u8 *rq_get_varlen_cdb(struct request *rq)
> +{
> + if (!rq->cmd_len && rq->varlen_cdb_len)
> + return rq->varlen_cdb;
> + else
> + return NULL;
> +}
These accessors look wrong ... I think what we want is rq_get_cdb and
rq_set_cdb that handles both <= BLK_MAX_CDB by simply a memcpy and >
BLK_MAX_CDB by setting up the large_cdb pointer. That way we can
accessorize the whole lot and the drivers don't have to care about what
BLK_MAX_CDB is set to (it simply becomes an internal convenience of
block ... and possibly allows us to eliminate the request carries
command data entirely).
> static inline int blk_queue_full(struct request_queue *q, int rw)
> {
> if (rw == READ)
James
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