On 03/14/2017 06:33 PM, Benjamin Block wrote:
> Hello Hannes,
>
> On Wed, Mar 01, 2017 at 10:15:20AM +0100, Hannes Reinecke wrote:
>> There hasn't been any reports for HBAs where asynchronous abort
>> would not work, so we should make it mandatory and remove
>> the fallback.
>>
>> Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
>> Reviewed-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
>> Reviewed-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
>> ---
>> Documentation/scsi/scsi_eh.txt | 18 ++++------
>> drivers/scsi/scsi_error.c | 81 ++++--------------------------------------
>> drivers/scsi/scsi_lib.c | 2 +-
>> drivers/scsi/scsi_priv.h | 3 +-
>> include/scsi/scsi_host.h | 5 ---
>> 5 files changed, 15 insertions(+), 94 deletions(-)
>>
>> diff --git a/Documentation/scsi/scsi_eh.txt b/Documentation/scsi/scsi_eh.txt
>> index 4edb9c1c..11e447b 100644
>> --- a/Documentation/scsi/scsi_eh.txt
>> +++ b/Documentation/scsi/scsi_eh.txt
>> @@ -70,7 +70,7 @@ with the command.
>> scmd is requeued to blk queue.
>>
>> - otherwise
>> - scsi_eh_scmd_add(scmd, 0) is invoked for the command. See
>> + scsi_eh_scmd_add(scmd) is invoked for the command. See
>> [1-3] for details of this function.
>>
>>
>> @@ -103,9 +103,7 @@ function
>> eh_timed_out() callback did not handle the command.
>> Step #2 is taken.
>>
>> - 2. If the host supports asynchronous completion (as indicated by the
>> - no_async_abort setting in the host template) scsi_abort_command()
>> - is invoked to schedule an asynchrous abort.
>> + 2. scsi_abort_command() is invoked to schedule an asynchrous abort.
>> Asynchronous abort are not invoked for commands which the
>> SCSI_EH_ABORT_SCHEDULED flag is set (this indicates that the command
>> already had been aborted once, and this is a retry which failed),
>> @@ -127,16 +125,13 @@ function
>>
>> scmds enter EH via scsi_eh_scmd_add(), which does the following.
>>
>> - 1. Turns on scmd->eh_eflags as requested. It's 0 for error
>> - completions and SCSI_EH_CANCEL_CMD for timeouts.
>> + 1. Links scmd->eh_entry to shost->eh_cmd_q
>>
>> - 2. Links scmd->eh_entry to shost->eh_cmd_q
>> + 2. Sets SHOST_RECOVERY bit in shost->shost_state
>>
>> - 3. Sets SHOST_RECOVERY bit in shost->shost_state
>> + 3. Increments shost->host_failed
>>
>> - 4. Increments shost->host_failed
>> -
>> - 5. Wakes up SCSI EH thread if shost->host_busy == shost->host_failed
>> + 4. Wakes up SCSI EH thread if shost->host_busy == shost->host_failed
>>
>> As can be seen above, once any scmd is added to shost->eh_cmd_q,
>> SHOST_RECOVERY shost_state bit is turned on. This prevents any new
>> @@ -252,7 +247,6 @@ scmd->allowed.
>>
>> 1. Error completion / time out
>> ACTION: scsi_eh_scmd_add() is invoked for scmd
>> - - set scmd->eh_eflags
>> - add scmd to shost->eh_cmd_q
>> - set SHOST_RECOVERY
>> - shost->host_failed++
>> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
>> index 802a081..7b70ee9 100644
>> --- a/drivers/scsi/scsi_error.c
>> +++ b/drivers/scsi/scsi_error.c
>> @@ -163,7 +163,7 @@ static int scsi_host_eh_past_deadline(struct Scsi_Host *shost)
>> }
>> }
>>
>> - scsi_eh_scmd_add(scmd, 0);
>> + scsi_eh_scmd_add(scmd);
>> }
>>
>> /**
>> @@ -217,9 +217,8 @@ static int scsi_host_eh_past_deadline(struct Scsi_Host *shost)
>> /**
>> * scsi_eh_scmd_add - add scsi cmd to error handling.
>> * @scmd: scmd to run eh on.
>> - * @eh_flag: optional SCSI_EH flag.
>> */
>> -void scsi_eh_scmd_add(struct scsi_cmnd *scmd, int eh_flag)
>> +void scsi_eh_scmd_add(struct scsi_cmnd *scmd)
>> {
>> struct Scsi_Host *shost = scmd->device->host;
>> unsigned long flags;
>> @@ -235,9 +234,6 @@ void scsi_eh_scmd_add(struct scsi_cmnd *scmd, int eh_flag)
>> if (shost->eh_deadline != -1 && !shost->last_reset)
>> shost->last_reset = jiffies;
>>
>> - if (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED)
>> - eh_flag &= ~SCSI_EH_CANCEL_CMD;
>> - scmd->eh_eflags |= eh_flag;
>> scsi_eh_reset(scmd);
>> list_add_tail(&scmd->eh_entry, &shost->eh_cmd_q);
>> shost->host_failed++;
>> @@ -271,10 +267,9 @@ enum blk_eh_timer_return scsi_times_out(struct request *req)
>> rtn = host->hostt->eh_timed_out(scmd);
>>
>> if (rtn == BLK_EH_NOT_HANDLED) {
>> - if (host->hostt->no_async_abort ||
>> - scsi_abort_command(scmd) != SUCCESS) {
>> + if (scsi_abort_command(scmd) != SUCCESS) {
>> set_host_byte(scmd, DID_TIME_OUT);
>> - scsi_eh_scmd_add(scmd, SCSI_EH_CANCEL_CMD);
>> + scsi_eh_scmd_add(scmd);
>> }
>> }
>>
>> @@ -327,7 +322,7 @@ static inline void scsi_eh_prt_fail_stats(struct Scsi_Host *shost,
>> list_for_each_entry(scmd, work_q, eh_entry) {
>> if (scmd->device == sdev) {
>> ++total_failures;
>> - if (scmd->eh_eflags & SCSI_EH_CANCEL_CMD)
>> + if (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED)
>> ++cmd_cancel;
>> else
>> ++cmd_failed;
>> @@ -1153,8 +1148,7 @@ int scsi_eh_get_sense(struct list_head *work_q,
>> * should not get sense.
>> */
>> list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
>> - if ((scmd->eh_eflags & SCSI_EH_CANCEL_CMD) ||
>> - (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED) ||
>> + if ((scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED) ||
>> SCSI_SENSE_VALID(scmd))
>> continue;
>>
>> @@ -1294,61 +1288,6 @@ static int scsi_eh_test_devices(struct list_head *cmd_list,
>> return list_empty(work_q);
>> }
>>
>> -
>> -/**
>> - * scsi_eh_abort_cmds - abort pending commands.
>> - * @work_q: &list_head for pending commands.
>> - * @done_q: &list_head for processed commands.
>> - *
>> - * Decription:
>> - * Try and see whether or not it makes sense to try and abort the
>> - * running command. This only works out to be the case if we have one
>> - * command that has timed out. If the command simply failed, it makes
>> - * no sense to try and abort the command, since as far as the shost
>> - * adapter is concerned, it isn't running.
>> - */
>> -static int scsi_eh_abort_cmds(struct list_head *work_q,
>> - struct list_head *done_q)
>> -{
>> - struct scsi_cmnd *scmd, *next;
>> - LIST_HEAD(check_list);
>> - int rtn;
>> - struct Scsi_Host *shost;
>> -
>> - list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
>> - if (!(scmd->eh_eflags & SCSI_EH_CANCEL_CMD))
>> - continue;
>> - shost = scmd->device->host;
>> - if (scsi_host_eh_past_deadline(shost)) {
>> - list_splice_init(&check_list, work_q);
>> - SCSI_LOG_ERROR_RECOVERY(3,
>> - scmd_printk(KERN_INFO, scmd,
>> - "%s: skip aborting cmd, past eh deadline\n",
>> - current->comm));
>> - return list_empty(work_q);
>> - }
>> - SCSI_LOG_ERROR_RECOVERY(3,
>> - scmd_printk(KERN_INFO, scmd,
>> - "%s: aborting cmd\n", current->comm));
>> - rtn = scsi_try_to_abort_cmd(shost->hostt, scmd);
>> - if (rtn == FAILED) {
>> - SCSI_LOG_ERROR_RECOVERY(3,
>> - scmd_printk(KERN_INFO, scmd,
>> - "%s: aborting cmd failed\n",
>> - current->comm));
>> - list_splice_init(&check_list, work_q);
>> - return list_empty(work_q);
>> - }
>> - scmd->eh_eflags &= ~SCSI_EH_CANCEL_CMD;
>> - if (rtn == FAST_IO_FAIL)
>> - scsi_eh_finish_cmd(scmd, done_q);
>> - else
>> - list_move_tail(&scmd->eh_entry, &check_list);
>> - }
>> -
>> - return scsi_eh_test_devices(&check_list, work_q, done_q, 0);
>> -}
>> -
>> /**
>> * scsi_eh_try_stu - Send START_UNIT to device.
>> * @scmd: &scsi_cmnd to send START_UNIT
>> @@ -1691,11 +1630,6 @@ static void scsi_eh_offline_sdevs(struct list_head *work_q,
>> sdev_printk(KERN_INFO, scmd->device, "Device offlined - "
>> "not ready after error recovery\n");
>> scsi_device_set_state(scmd->device, SDEV_OFFLINE);
>> - if (scmd->eh_eflags & SCSI_EH_CANCEL_CMD) {
>> - /*
>> - * FIXME: Handle lost cmds.
>> - */
>> - }
>> scsi_eh_finish_cmd(scmd, done_q);
>> }
>> return;
>> @@ -2139,8 +2073,7 @@ static void scsi_unjam_host(struct Scsi_Host *shost)
>> SCSI_LOG_ERROR_RECOVERY(1, scsi_eh_prt_fail_stats(shost, &eh_work_q));
>>
>> if (!scsi_eh_get_sense(&eh_work_q, &eh_done_q))
>> - if (!scsi_eh_abort_cmds(&eh_work_q, &eh_done_q))
>> - scsi_eh_ready_devs(shost, &eh_work_q, &eh_done_q);
>> + scsi_eh_ready_devs(shost, &eh_work_q, &eh_done_q);
>>
>> spin_lock_irqsave(shost->host_lock, flags);
>> if (shost->eh_deadline != -1)
>> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
>> index 0735a46..98b2df8 100644
>> --- a/drivers/scsi/scsi_lib.c
>> +++ b/drivers/scsi/scsi_lib.c
>> @@ -1593,7 +1593,7 @@ static void scsi_softirq_done(struct request *rq)
>> scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
>> break;
>> default:
>> - scsi_eh_scmd_add(cmd, 0);
>> + scsi_eh_scmd_add(cmd);
>> break;
>> }
>> }
>> diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
>> index 5be6cbf6..e20ab10 100644
>> --- a/drivers/scsi/scsi_priv.h
>> +++ b/drivers/scsi/scsi_priv.h
>> @@ -18,7 +18,6 @@
>> /*
>> * Scsi Error Handler Flags
>> */
>> -#define SCSI_EH_CANCEL_CMD 0x0001 /* Cancel this cmd */
>> #define SCSI_EH_ABORT_SCHEDULED 0x0002 /* Abort has been scheduled */
>>
>> #define SCSI_SENSE_VALID(scmd) \
>> @@ -72,7 +71,7 @@ extern int scsi_dev_info_list_add_keyed(int compatible, char *vendor,
>> extern int scsi_error_handler(void *host);
>> extern int scsi_decide_disposition(struct scsi_cmnd *cmd);
>> extern void scsi_eh_wakeup(struct Scsi_Host *shost);
>> -extern void scsi_eh_scmd_add(struct scsi_cmnd *, int);
>> +extern void scsi_eh_scmd_add(struct scsi_cmnd *);
>> void scsi_eh_ready_devs(struct Scsi_Host *shost,
>> struct list_head *work_q,
>> struct list_head *done_q);
>> diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
>> index 3cd8c3b..afb0481 100644
>> --- a/include/scsi/scsi_host.h
>> +++ b/include/scsi/scsi_host.h
>> @@ -452,11 +452,6 @@ struct scsi_host_template {
>> unsigned no_write_same:1;
>>
>> /*
>> - * True if asynchronous aborts are not supported
>> - */
>> - unsigned no_async_abort:1;
>> -
>> - /*
>> * Countdown for host blocking with no commands outstanding.
>> */
>> unsigned int max_host_blocked;
>> --
>> 1.8.5.6
>>
>
> Hmm so, I guess we compromise in terms of how granular we want to
> recover?
>
> When say an abort for command A on LUN 1 behind Port α fails for some
> reason, then we also skip all possible aborts for command B on LUN 2
> behind Port α and command C on LUN 1 behind Port β? (The host might
> already be in recovery by the time command B and C fail)
>
No.
Recovery will only be started once all commands have been completed or
aborted.
Hence will be be aborting all commands before entering SCSI EH.
> I mean, in the end, all traffic holds on that host anyway, as long as we
> get into EH - which is true as soon as one abort fails. Might as well
> skip the wait time till we get there.
>
There still is a benefit to be had from sending individual aborts; after
all, the commands are supposed to be independently, and sending an abort
serves as a pointer to the LLDD to remove any reference to it.
> I would like it, if we could document that fact a bit more direct.
> Otherwise I think that's good. The code also looks good.
>
>
> Reviewed-by: Benjamin Block <bblock@xxxxxxxxxxxxxxxxxx>
>
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@xxxxxxx +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
