On 08/26/2009 09:17 AM, Martin K. Petersen wrote:
> DIF Type 2 drives require 32-byte commands. Add a suitable flag to
> struct scsi_device that will cause scsi_setup_fs_cmnd() to allocate a
> bigger command buffer.
>
> Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
> ---
> drivers/scsi/scsi_lib.c | 36 +++++++++++++++++++++++++++++++++++-
> include/scsi/scsi.h | 1 +
> include/scsi/scsi_device.h | 1 +
> 3 files changed, 37 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 662024d..fc752b5 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -67,6 +67,9 @@ static struct scsi_host_sg_pool scsi_sg_pools[] = {
>
> struct kmem_cache *scsi_sdb_cache;
>
> +struct kmem_cache *cdb_cache;
> +mempool_t *cdb_pool;
> +
> static void scsi_run_queue(struct request_queue *q);
>
> /*
> @@ -642,6 +645,10 @@ static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
>
> if (scsi_prot_sg_count(cmd))
> scsi_free_sgtable(cmd->prot_sdb);
> +
> + if (cmd->cmd_len == SCSI_EXT_CDB_SIZE)
> + mempool_free(cmd->cmnd, cdb_pool);
> +
This will not work. The cmd->cmnd might happen to be form an upper
layer through bsg or blk_execute_xxx and might just be SCSI_EXT_CDB_SIZE.
We could say to maybe:
if (cmd->cmnd != cmd->req->cmd)
which means scsi allocated the buffer and not use the block supplied one
but that might be dangerous and will need a fat comment that states that
scsi drivers must use the scsi_cmnd pointer and not the request's.
Alternatively you could:
if ((cmd->cmd_len == SCSI_EXT_CDB_SIZE) && blk_fs_request(cmnd->req))
since variable length can only come BLOCK_PC currently. But this will need to change
again later when ULDs might want to issue other commands that are SCSI_EXT_CDB_SIZE
in the future, which again might be dangerous.
or use an extra flag. You could use the first "fat comment" option above, all the drivers
I know do only use the scsi_cmnd->cmnd pointer.
> }
>
> /*
> @@ -1109,7 +1116,18 @@ int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
> if (unlikely(!cmd))
> return BLKPREP_DEFER;
>
> - memset(cmd->cmnd, 0, BLK_MAX_CDB);
> + if (sdev->use_32_for_rw) {
> + req->cmd = mempool_alloc(cdb_pool, GFP_ATOMIC);
> +
James could we get that live-lock problem we had when not
atomically allocating the scsi_cmnd, (when sense was separated
out)
> + if (unlikely(!req->cmd))
> + return BLKPREP_DEFER;
> +
> + cmd->cmnd = req->cmd;
> + cmd->cmd_len = req->cmd_len = SCSI_EXT_CDB_SIZE;
> + memset(cmd->cmnd, 0, cmd->cmd_len);
> + } else
> + memset(cmd->cmnd, 0, BLK_MAX_CDB);
> +
> return scsi_init_io(cmd, GFP_ATOMIC);
> }
> EXPORT_SYMBOL(scsi_setup_fs_cmnd);
> @@ -1745,6 +1763,19 @@ int __init scsi_init_queue(void)
> }
> }
>
> + cdb_cache = kmem_cache_create("scsi_cdb_32", SCSI_EXT_CDB_SIZE,
> + 0, 0, NULL);
> + if (!cdb_cache) {
> + printk(KERN_ERR "SCSI: can't init scsi cdb cache\n");
> + goto cleanup_sdb;
> + }
> +
> + cdb_pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE, cdb_cache);
> + if (!cdb_pool) {
> + printk(KERN_ERR "SCSI: can't init scsi cdb pool\n");
> + goto cleanup_sdb;
> + }
> +
> return 0;
>
> cleanup_sdb:
> @@ -1771,6 +1802,9 @@ void scsi_exit_queue(void)
> mempool_destroy(sgp->pool);
> kmem_cache_destroy(sgp->slab);
> }
> +
> + mempool_destroy(cdb_pool);
> + kmem_cache_destroy(cdb_cache);
> }
>
> /**
> diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
> index 084478e..a7ae10a 100644
> --- a/include/scsi/scsi.h
> +++ b/include/scsi/scsi.h
> @@ -138,6 +138,7 @@ struct scsi_cmnd;
> * SCSI command lengths
> */
>
> +#define SCSI_EXT_CDB_SIZE 32
> #define SCSI_MAX_VARLEN_CDB_SIZE 260
>
> /* defined in T10 SCSI Primary Commands-2 (SPC2) */
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index 3f566af..de2966b 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -129,6 +129,7 @@ struct scsi_device {
> * this device */
> unsigned expecting_cc_ua:1; /* Expecting a CHECK_CONDITION/UNIT_ATTN
> * because we did a bus reset. */
> + unsigned use_32_for_rw:1; /* use 32-byte read / write (DIF Type 2) */
> unsigned use_10_for_rw:1; /* first try 10-byte read / write */
> unsigned use_10_for_ms:1; /* first try 10-byte mode sense/select */
> unsigned skip_ms_page_8:1; /* do not use MODE SENSE page 0x08 */
Boaz
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