Note: in addition to the block layer tag changes, you also need the patch sent
to this list separately under
[PATCH 2.5.17] Making SCSI not copy the request structure
To make all this work.
The essential features of this are:
Extra functions to:
- Find a tag given the Scsi_Device
- find a scsi device given the host, pun and lun
Should process generic tags correctly in the requests.
Adds a use_blk_tcq flag in the host structure to turn on using the generic tcq
functions.
comments welcome.
James Bottomley
PS I have this up and running on my build system and it seems stable.
However, there were a lot of subtle (and data eating) errors getting to this
stage so use at your own risk.
# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
# ChangeSet 1.583 -> 1.585
# drivers/scsi/hosts.c 1.8 -> 1.9
# drivers/scsi/scsi.h 1.13 -> 1.15
# drivers/scsi/hosts.h 1.8 -> 1.10
# drivers/scsi/scsi_lib.c 1.23 -> 1.25
# drivers/scsi/scsi.c 1.29 -> 1.30
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/06/02 jejb@mulgrave.(none) 1.584
# Initial support (mid-layer) for generic TCQ
# --------------------------------------------
# 02/06/09 jejb@mulgrave.(none) 1.369.88.2
# [SCSI 53c700] bux fix in tag starvation, cosmetic cleanup of set_depth
# --------------------------------------------
# 02/06/09 jejb@mulgrave.(none) 1.369.88.3
# [SCSI 53c700] update version to 2.8
# --------------------------------------------
# 02/06/10 jejb@mulgrave.(none) 1.585
# [SCSI mid-layer]
#
# Add support for generic blk layer TCQ (needs blk_queue_find_tag
# function)
# --------------------------------------------
#
diff -Nru a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
--- a/drivers/scsi/hosts.c Mon Jun 10 22:51:46 2002
+++ b/drivers/scsi/hosts.c Mon Jun 10 22:51:46 2002
@@ -230,6 +230,7 @@
retval->select_queue_depths = tpnt->select_queue_depths;
retval->max_sectors = tpnt->max_sectors;
+ retval->use_blk_tcq = tpnt->use_blk_tcq;
if(!scsi_hostlist)
scsi_hostlist = retval;
diff -Nru a/drivers/scsi/hosts.h b/drivers/scsi/hosts.h
--- a/drivers/scsi/hosts.h Mon Jun 10 22:51:46 2002
+++ b/drivers/scsi/hosts.h Mon Jun 10 22:51:46 2002
@@ -286,6 +286,12 @@
unsigned highmem_io:1;
+ /*
+ * True if the driver wishes to use the generic block layer
+ * tag queueing functions
+ */
+ unsigned use_blk_tcq:1;
+
/*
* Name of proc directory
*/
@@ -386,6 +392,7 @@
unsigned unchecked_isa_dma:1;
unsigned use_clustering:1;
unsigned highmem_io:1;
+ unsigned use_blk_tcq:1;
/*
* Host has rejected a command because it was busy.
@@ -555,6 +562,26 @@
#define SD_EXTRA_DEVS CONFIG_SD_EXTRA_DEVS
#define SR_EXTRA_DEVS CONFIG_SR_EXTRA_DEVS
+
+/**
+ * scsi_find_device - find a device given the host
+ * @channel: SCSI channel (zero if only one channel)
+ * @pun: SCSI target number (physical unit number)
+ * @lun: SCSI Logical Unit Number
+ **/
+static inline Scsi_Device *scsi_find_device(struct Scsi_Host *host,
+ int channel, int pun, int lun) {
+ Scsi_Device *SDpnt;
+
+ for(SDpnt = host->host_queue;
+ SDpnt != NULL;
+ SDpnt = SDpnt->next)
+ if(SDpnt->channel == channel && SDpnt->id == pun
+ && SDpnt->lun ==lun)
+ break;
+ return SDpnt;
+}
+
#endif
/*
* Overrides for Emacs so that we follow Linus's tabbing style.
diff -Nru a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
--- a/drivers/scsi/scsi.c Mon Jun 10 22:51:46 2002
+++ b/drivers/scsi/scsi.c Mon Jun 10 22:51:46 2002
@@ -254,10 +254,19 @@
static void scsi_wait_done(Scsi_Cmnd * SCpnt)
{
- struct request *req;
+ struct request *req = SCpnt->request;
+ struct request_queue *q = &SCpnt->device->request_queue;
+ unsigned long flags;
- req = SCpnt->request;
+ ASSERT_LOCK(q->queue_lock, 0);
req->rq_status = RQ_SCSI_DONE; /* Busy, but indicate request done */
+
+ spin_lock_irqsave(q->queue_lock, flags);
+
+ if(blk_rq_tagged(req))
+ blk_queue_end_tag(q, req);
+
+ spin_unlock_irqrestore(q->queue_lock, flags);
if (req->waiting)
complete(req->waiting);
diff -Nru a/drivers/scsi/scsi.h b/drivers/scsi/scsi.h
--- a/drivers/scsi/scsi.h Mon Jun 10 22:51:46 2002
+++ b/drivers/scsi/scsi.h Mon Jun 10 22:51:46 2002
@@ -560,6 +560,7 @@
atomic_t device_active; /* commands checked out for device */
volatile unsigned short device_busy; /* commands actually active on low-level */
Scsi_Cmnd *device_queue; /* queue of SCSI Command structures */
+ Scsi_Cmnd *current_cmnd; /* currently active command */
unsigned int id, lun, channel;
@@ -849,6 +850,89 @@
#define SCSI_TRY_RESET_HOST 3
extern int scsi_reset_provider(Scsi_Device *, int);
+
+/**
+ * scsi_activate_tcq - turn on tag command queueing
+ * @SDpnt: device to turn on TCQ for
+ * @depth: queue depth
+ *
+ * Notes:
+ * Eventually, I hope depth would be the maximum depth
+ * the device could cope with and the real queue depth
+ * would be adjustable from 0 to depth.
+ **/
+static inline void scsi_activate_tcq(Scsi_Device *SDpnt, int depth) {
+ request_queue_t *q = &SDpnt->request_queue;
+
+ if(SDpnt->tagged_supported && !blk_queue_tagged(q)) {
+ blk_queue_init_tags(q, depth);
+ SDpnt->tagged_queue = 1;
+ }
+}
+
+/**
+ * scsi_deactivate_tcq - turn off tag command queueing
+ * @SDpnt: device to turn off TCQ for
+ **/
+static inline void scsi_deactivate_tcq(Scsi_Device *SDpnt) {
+ blk_queue_free_tags(&SDpnt->request_queue);
+ SDpnt->tagged_queue = 0;
+}
+#define MSG_SIMPLE_TAG 0x20
+#define MSG_HEAD_TAG 0x21
+#define MSG_ORDERED_TAG 0x22
+
+#define SCSI_NO_TAG (-1) /* identify no tag in use */
+
+/**
+ * scsi_populate_tag_msg - place a tag message in a buffer
+ * @SCpnt: pointer to the Scsi_Cmnd for the tag
+ * @msg: pointer to the area to place the tag
+ *
+ * Notes:
+ * designed to create the correct type of tag message for the
+ * particular request. Returns the size of the tag message.
+ * May return 0 if TCQ is disabled for this device.
+ **/
+static inline int scsi_populate_tag_msg(Scsi_Cmnd *SCpnt, char *msg) {
+ struct request *req = SCpnt->request;
+
+ if(!blk_rq_tagged(req))
+ return 0;
+
+ if(req->flags & REQ_BARRIER)
+ *msg++ = MSG_ORDERED_TAG;
+ else
+ *msg++ = MSG_SIMPLE_TAG;
+
+ *msg++ = SCpnt->request->tag;
+
+ return 2;
+}
+
+/**
+ * scsi_find_tag - find a tagged command by device
+ * @SDpnt: pointer to the ScSI device
+ * @tag: the tag number
+ *
+ * Notes:
+ * Only works with tags allocated by the generic blk layer.
+ **/
+static inline Scsi_Cmnd *scsi_find_tag(Scsi_Device *SDpnt, int tag) {
+
+ struct request *req;
+
+ if(tag == SCSI_NO_TAG)
+ /* single command, look in space */
+ return SDpnt->current_cmnd;
+
+ req = blk_queue_find_tag(&SDpnt->request_queue, tag);
+
+ if(req == NULL)
+ return NULL;
+
+ return (Scsi_Cmnd *)req->special;
+}
#endif
diff -Nru a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
--- a/drivers/scsi/scsi_lib.c Mon Jun 10 22:51:46 2002
+++ b/drivers/scsi/scsi_lib.c Mon Jun 10 22:51:46 2002
@@ -76,7 +76,8 @@
* must not attempt merges on this) and that it acts as a soft
* barrier
*/
- rq->flags = REQ_SPECIAL | REQ_BARRIER;
+ rq->flags &= REQ_QUEUED;
+ rq->flags |= REQ_SPECIAL | REQ_BARRIER;
rq->special = data;
@@ -87,6 +88,9 @@
* device, or a host that is unable to accept a particular command.
*/
spin_lock_irqsave(q->queue_lock, flags);
+ /* If command is tagged, release the tag */
+ if(blk_rq_tagged(rq))
+ blk_queue_end_tag(q, rq);
_elv_add_request(q, rq, !at_head, 0);
q->request_fn(q);
spin_unlock_irqrestore(q->queue_lock, flags);
@@ -378,6 +382,9 @@
add_blkdev_randomness(major(req->rq_dev));
+ if(blk_rq_tagged(req))
+ blk_queue_end_tag(q, req);
+
end_that_request_last(req);
spin_unlock_irqrestore(q->queue_lock, flags);
@@ -924,8 +931,13 @@
* reason to search the list, because all of the commands
* in this queue are for the same device.
*/
- blkdev_dequeue_request(req);
+ if(!(blk_queue_tagged(q) && (blk_queue_start_tag(q, req) == 0)))
+ blkdev_dequeue_request(req);
+ /* note the overloading of req->special. When the tag
+ * is active it always means SCpnt. If the tag goes
+ * back for re-queueing, it may be reset */
+ req->special = SCpnt;
SCpnt->request = req;
/*
