On 6/29/20 2:48 PM, John Garry wrote:
On 29/06/2020 08:20, Hannes Reinecke wrote:
Add helper functions to allow LLDDs to allocate and free
internal commands.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
drivers/scsi/scsi_lib.c | 44
++++++++++++++++++++++++++++++++++++++++++++
include/scsi/scsi_device.h | 4 ++++
2 files changed, 48 insertions(+)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0ba7a65e7c8d..c2277eff4e06 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1903,6 +1903,50 @@ void scsi_mq_destroy_tags(struct Scsi_Host *shost)
blk_mq_free_tag_set(&shost->tag_set);
}
+/**
+ * scsi_get_internal_cmd - allocate an internal SCSI command
+ * @sdev: SCSI device from which to allocate the command
+ * @data_direction: Data direction for the allocated command
+ * @op_flags: request allocation flags
+ *
+ * Allocates a SCSI command for internal LLDD use.
+ */
+struct scsi_cmnd *scsi_get_internal_cmd(struct scsi_device *sdev,
+ enum dma_data_direction data_direction, int op_flags)
+{
+ struct request *rq;
+ struct scsi_cmnd *scmd;
+ blk_mq_req_flags_t flags = 0;
+ unsigned int op = REQ_INTERNAL | op_flags;
+
+ op |= (data_direction == DMA_TO_DEVICE) ?
+ REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN;
As an aside, REQ_OP_SCSI_OUT seems to have same effect as
REQ_OP_SCSI_IN, as we only ever check if either is set, here:
bool blk_op_is_scsi(unsigned int op)
{
return op == REQ_OP_SCSI_OUT || op == REQ_OP_SCSI_IN;
}
but maybe I missed something.
Indeed you do :-)
That's one of the best-kept secrets in the block layer:
op_is_write()
The assumption is that every request with a REQ_OP which has the lowest
bit set is a write.
And quite a lot of accounting the the block layer revolves around that.
So we'll need to keep it.
... and we probably should document it somewhere.
+ rq = blk_mq_alloc_request(sdev->request_queue, op, flags);
+ if (IS_ERR(rq))
+ return NULL;
+ scmd = blk_mq_rq_to_pdu(rq);
+ scmd->request = rq;
+ scmd->device = sdev;
+ return scmd;
+}
+EXPORT_SYMBOL_GPL(scsi_get_internal_cmd);
+
+/**
+ * scsi_put_internal_cmd - free an internal SCSI command
+ * @scmd: SCSI command to be freed
+ *
+ * Check if @scmd is an internal command, and call
+ * blk_mq_free_request() if true.
+ */
+void scsi_put_internal_cmd(struct scsi_cmnd *scmd)
+{
+ struct request *rq = blk_mq_rq_from_pdu(scmd);
+
+ if (blk_rq_is_internal(rq))
+ blk_mq_free_request(rq);
I haven't gone through all users in the series, but is it worth warning
when we're passed a scmd which isn't an internal command? Doing so seems
a programming error which we should yell about.
Will be part of the next round; others have complained, too.
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
