On 5/24/20 5:58 PM, Douglas Gilbert wrote:
When the __scsi_device_lookup() function is given a "ctl" (i.e. the
latter part of "hctl" tuple), improve the loop to find a matching
device (LU) in the given host. Rather than loop over all LUs in the
host, first loop over all targets to find a match on "ct" then, if
found, loop over all LUs in that target for a match on "l". These
nested loops are better since they don't visit LUs belonging to
non-matching targets. This improvement flows through to the locked
version of this function, namely scsi_device_lookup().
Remove a 21 year old comment by the author that no longer seem
relevant.
Signed-off-by: Douglas Gilbert <dgilbert@xxxxxxxxxxxx>
---
drivers/scsi/scsi.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 0fb650aebcfb..9e7658aebdb7 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -35,7 +35,6 @@
*
* Jiffies wrap fixes (host->resetting), 3 Dec 1998 Andrea Arcangeli
*
- * out_of_space hacks, D. Gilbert (dpg) 990608
*/
#include <linux/module.h>
@@ -789,16 +788,31 @@ EXPORT_SYMBOL(scsi_device_lookup_by_target);
struct scsi_device *__scsi_device_lookup(struct Scsi_Host *shost,
uint channel, uint id, u64 lun)
{
- unsigned long l_idx;
+ unsigned long l_idx, m_idx;
+ struct scsi_target *starg;
struct scsi_device *sdev;
- xa_for_each_marked(&shost->__devices, l_idx, sdev,
+ if (xa_empty(&shost->__devices))
+ return NULL;
+ if (xa_empty(&shost->__targets))
+ goto inconsistent;
+ xa_for_each(&shost->__targets, l_idx, starg) {
+ if (!(starg->id == id && starg->channel == channel))
+ continue;
+ xa_for_each_marked(&starg->devices, m_idx, sdev,
+ SCSI_XA_NON_SDEV_DEL) {
+ if (sdev->lun == lun)
+ return sdev;
+ }
+ }
+ return NULL;
+inconsistent:
+ xa_for_each_marked(&shost->__devices, m_idx, sdev,
SCSI_XA_NON_SDEV_DEL) {
- if (sdev->channel == channel && sdev->id == id &&
- sdev->lun ==lun)
+ if (sdev->id == id && sdev->channel == channel &&
+ sdev->lun == lun)
return sdev;
}
-
return NULL;
}
EXPORT_SYMBOL(__scsi_device_lookup);
... and if we had been using the LUN as an index we could have using
'xa_load()' directly without needing any loop ...
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
