[PATCH v4 09/10] libsas: pre-clean commands that won the eh vs completion race

Dan Williams
2012-01-17T05:11:48Z

When scrolling forward through the eh list (in a clear_q scenario) it is
possible to encounter commands that won the completion vs eh race. Rather
than sprinkle more "if (!task)" throughout the handler just make a pass
through the list and delete the race winners before handling the rest.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
drivers/scsi/libsas/sas_scsi_host.c | 25 ++++++++++++++++---------
1 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/libsas/sas_scsi_host.c b/drivers/scsi/libsas/sas_scsi_host.c
index 94ef763..731c892 100644
--- a/drivers/scsi/libsas/sas_scsi_host.c
+++ b/drivers/scsi/libsas/sas_scsi_host.c
@@ -249,8 +249,8 @@ out_done:

static void sas_eh_finish_cmd(struct scsi_cmnd *cmd)
{
- struct sas_task *task = TO_SAS_TASK(cmd);
struct sas_ha_struct *sas_ha = SHOST_TO_SAS_HA(cmd->device->host);
+ struct sas_task *task = TO_SAS_TASK(cmd);

/* At this point, we only get called following an actual abort
* of the task, so we should be guaranteed not to be racing with
@@ -267,9 +267,9 @@ static void sas_eh_finish_cmd(struct scsi_cmnd *cmd)

static void sas_eh_defer_cmd(struct scsi_cmnd *cmd)
{
- struct sas_task *task = TO_SAS_TASK(cmd);
- struct domain_device *dev = task->dev;
+ struct domain_device *dev = cmd_to_domain_dev(cmd);
struct sas_ha_struct *ha = dev->port->ha;
+ struct sas_task *task = TO_SAS_TASK(cmd);

if (!dev_is_sata(dev)) {
sas_eh_finish_cmd(cmd);
@@ -530,8 +530,9 @@ static int sas_eh_handle_sas_errors(struct Scsi_Host *shost,
struct sas_internal *i = to_sas_internal(shost->transportt);
unsigned long flags;
struct sas_ha_struct *ha = SHOST_TO_SAS_HA(shost);
+ LIST_HEAD(done);

-Again:
+ /* clean out any commands that won the completion vs eh race */
list_for_each_entry_safe(cmd, n, work_q, eh_entry) {
struct domain_device *dev = cmd_to_domain_dev(cmd);
struct sas_task *task;
@@ -545,7 +546,12 @@ Again:
spin_unlock_irqrestore(&dev->done_lock, flags);

if (!task)
- continue;
+ list_move_tail(&cmd->eh_entry, &done);
+ }
+
+ Again:
+ list_for_each_entry_safe(cmd, n, work_q, eh_entry) {
+ struct sas_task *task = TO_SAS_TASK(cmd);

list_del_init(&cmd->eh_entry);

@@ -649,15 +655,16 @@ Again:
goto clear_q;
}
}
+ out:
+ list_splice_tail(&done, work_q);
list_splice_tail_init(&ha->eh_ata_q, work_q);
return list_empty(work_q);
-clear_q:
+
+ clear_q:
SAS_DPRINTK("--- Exit %s -- clear_q\n", __func__);
list_for_each_entry_safe(cmd, n, work_q, eh_entry)
sas_eh_finish_cmd(cmd);
-
- list_splice_tail_init(&ha->eh_ata_q, work_q);
- return list_empty(work_q);
+ goto out;
}

void sas_scsi_recover_host(struct Scsi_Host *shost)