Following discussions which resulted from the:
[RFC] target code updates to support scanned targets
http://marc.theaimsgroup.com/?l=linux-scsi&m=110850749515984&w=2
thread, the overall consensus seems to be that transport-classes
should support a 'true-hotplug' mechanism of device discovery and
removal (this involves both registration and lun-scanning). In order
to facilitate this ability and to not constrain the LLDD from the
typical restrictions of the storage scanning process:
* must be done from process context -- depending on transport type,
discovery can occur from a non-process context
* potentially _long_ scan times -- even if discovery is done from a
'sleeping' capable context, halting a LLDD for discovery purposes
is typically undesirable.
I'd like to propose the addition of a per-Scsi_Host work-queue to
manage these scanning as well as any other (relevant)
lower-level-driver differed requests.
The attached patch adds:
1) a new scsi-host template member 'create_work_queue' which when set
will create a single-threaded (the per-CPU option seemed too
heavyweight) work-queue.
2) an exported helper function scsi_queue_work() to queue the work to
the scsi-host work-queue.
the interface was kept flexible -- queuing of a work_struct object
rather than adding small wrapper functions to perform distinct
operations (i.e. scsi_scan_target_deferred(...), etc) so that any
'deferred' action could be requested by a transport-class or LLDD.
Example usage:
scsi_transport_fc.h:
struct fc_rport {
...
struct work_struct scan_work;
} __attribute__((aligned(sizeof(unsigned long))));
scsi_transport_fc.c:
...
static void fc_scan_rport_work(void *data)
{
struct fc_rport *rport = (struct fc_rport *)data;
scsi_scan_target(&rport->dev, rport->channel,
rport->scsi_target_id, SCAN_WILD_CARD, 0);
}
struct fc_rport *
fc_create_rport(struct Scsi_Host *shost, int channel,
struct fc_rport_identifiers *ids)
{
...
INIT_WORK(&rport->scan_work,
fc_scan_rport_work, rport);
...
void
fc_remote_port_unblock(struct fc_rport *rport)
{
struct Scsi_Host *shost = rport_to_shost(rport);
...
if (rport->port_state == FC_PORTSTATE_OFFLINE)
/* Initiate a full rescan, as all
* scsi_target objects have been previously
* torn-down. */
scsi_queue_work(shost, &rport->scan_work);
else
scsi_target_unblock(&rport->dev);
Anyway, comments?
--
Andrew Vasquez
===== drivers/scsi/hosts.c 1.107 vs edited =====
--- 1.107/drivers/scsi/hosts.c 2005-01-18 11:15:06 -08:00
+++ edited/drivers/scsi/hosts.c 2005-02-21 15:10:38 -08:00
@@ -160,6 +160,9 @@ static void scsi_host_dev_release(struct
shost->eh_notify = NULL;
}
+ if (shost->create_work_queue)
+ destroy_workqueue(shost->work_q);
+
scsi_proc_hostdir_rm(shost->hostt);
scsi_destroy_command_freelist(shost);
kfree(shost->shost_data);
@@ -247,6 +250,7 @@ struct Scsi_Host *scsi_host_alloc(struct
shost->cmd_per_lun = sht->cmd_per_lun;
shost->unchecked_isa_dma = sht->unchecked_isa_dma;
shost->use_clustering = sht->use_clustering;
+ shost->create_work_queue = sht->create_work_queue;
if (sht->max_host_blocked)
shost->max_host_blocked = sht->max_host_blocked;
@@ -285,16 +289,27 @@ struct Scsi_Host *scsi_host_alloc(struct
snprintf(shost->shost_classdev.class_id, BUS_ID_SIZE, "host%d",
shost->host_no);
+ if (shost->create_work_queue) {
+ snprintf(shost->work_q_name, KOBJ_NAME_LEN, "scsi_wq_%d",
+ shost->host_no);
+ shost->work_q = create_singlethread_workqueue(
+ shost->work_q_name);
+ if (!shost->work_q)
+ goto fail_destroy_freelist;
+ }
+
shost->eh_notify = &complete;
rval = kernel_thread(scsi_error_handler, shost, 0);
if (rval < 0)
- goto fail_destroy_freelist;
+ goto fail_destroy_workqueue;
wait_for_completion(&complete);
shost->eh_notify = NULL;
scsi_proc_hostdir_add(shost->hostt);
return shost;
+ fail_destroy_workqueue:
+ destroy_workqueue(shost->work_q);
fail_destroy_freelist:
scsi_destroy_command_freelist(shost);
fail_kfree:
@@ -392,3 +407,26 @@ int scsi_is_host_device(const struct dev
return dev->release == scsi_host_dev_release;
}
EXPORT_SYMBOL(scsi_is_host_device);
+
+/**
+ * scsi_queue_work - Queue work to the Scsi_Host workqueue.
+ * @shost: Pointer to Scsi_Host.
+ * @work: Work to queue for execution.
+ *
+ * Return value:
+ * 0 on success / != 0 for error
+ **/
+int scsi_queue_work(struct Scsi_Host *shost, struct work_struct *work)
+{
+ if (unlikely(!shost->create_work_queue)) {
+ printk(KERN_ERR
+ "ERROR: Scsi host '%s' attempted to queue scsi-work, "
+ "when no workqueue created.\n", shost->hostt->name);
+ dump_stack();
+
+ return -EINVAL;
+ }
+
+ return queue_work(shost->work_q, work);
+}
+EXPORT_SYMBOL_GPL(scsi_queue_work);
===== include/scsi/scsi_host.h 1.26 vs edited =====
--- 1.26/include/scsi/scsi_host.h 2005-01-19 08:01:21 -08:00
+++ edited/include/scsi/scsi_host.h 2005-02-21 12:13:32 -08:00
@@ -4,6 +4,7 @@
#include <linux/device.h>
#include <linux/list.h>
#include <linux/types.h>
+#include <linux/workqueue.h>
struct block_device;
struct module;
@@ -363,6 +364,11 @@ struct scsi_host_template {
unsigned skip_settle_delay:1;
/*
+ * True if a work-queue should be created for shost processing.
+ */
+ unsigned create_work_queue:1;
+
+ /*
* Countdown for host blocking with no commands outstanding
*/
unsigned int max_host_blocked;
@@ -501,6 +507,11 @@ struct Scsi_Host {
*/
unsigned reverse_ordering:1;
+ unsigned create_work_queue:1;
+
+ char work_q_name[KOBJ_NAME_LEN];
+ struct workqueue_struct *work_q;
+
/*
* Host has rejected a command because it was busy.
*/
@@ -598,6 +609,7 @@ extern void scsi_free_host_dev(struct sc
extern struct scsi_device *scsi_get_host_dev(struct Scsi_Host *);
int scsi_is_host_device(const struct device *);
+extern int scsi_queue_work(struct Scsi_Host *, struct work_struct *);
/* legacy interfaces */
extern struct Scsi_Host *scsi_register(struct scsi_host_template *, int);
-
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