From: Hannes Reinecke <hare@xxxxxxx>
As we already know the index of the requested target in
scsi_alloc_target() we can try to fetch it first before trying
to allocate a new one. This will save us a pointless memory
allocation in case the target is already present and uncontended.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
drivers/scsi/scsi_scan.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 8afb71c036d5..41818111808e 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -387,7 +387,7 @@ static void scsi_target_reap_ref_put(struct scsi_target *starget)
* is responsible for both reaping and doing a last put
*/
static struct scsi_target *scsi_alloc_target(struct device *parent,
- int channel, uint id)
+ u16 channel, u16 id)
{
struct Scsi_Host *shost = dev_to_shost(parent);
struct device *dev = NULL;
@@ -397,7 +397,23 @@ static struct scsi_target *scsi_alloc_target(struct device *parent,
struct scsi_target *starget;
struct scsi_target *found_target;
int error, ref_got;
- unsigned long tid;
+ unsigned long tid = (channel << 16) | id;
+
+ /*
+ * Try if the target is already present, and save us
+ * a pointless memory allocation if so.
+ */
+ spin_lock_irqsave(shost->host_lock, flags);
+ found_target = xa_load(&shost->__targets, tid);
+ if (found_target) {
+ get_device(&found_target->dev);
+ if (kref_get_unless_zero(&found_target->reap_ref)) {
+ spin_unlock_irqrestore(shost->host_lock, flags);
+ return found_target;
+ }
+ put_device(&found_target->dev);
+ }
+ spin_unlock_irqrestore(shost->host_lock, flags);
starget = kzalloc(size, GFP_KERNEL);
if (!starget) {
@@ -418,7 +434,6 @@ static struct scsi_target *scsi_alloc_target(struct device *parent,
starget->state = STARGET_CREATED;
starget->scsi_level = SCSI_2;
starget->max_target_blocked = SCSI_DEFAULT_TARGET_BLOCKED;
- tid = scsi_target_index(starget);
retry:
spin_lock_irqsave(shost->host_lock, flags);
found_target = xa_load(&shost->__targets, tid);
--
2.25.1
