[PATCH 6.1 187/219] scsi: core: Move scsi_host_busy() out of host lock for waking up EH handler

Greg Kroah-Hartman
2024-02-03T04:10:52Z

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 4373534a9850627a2695317944898eb1283a2db0 ]

Inside scsi_eh_wakeup(), scsi_host_busy() is called & checked with host
lock every time for deciding if error handler kthread needs to be waken up.

This can be too heavy in case of recovery, such as:

- N hardware queues

- queue depth is M for each hardware queue

- each scsi_host_busy() iterates over (N * M) tag/requests

If recovery is triggered in case that all requests are in-flight, each
scsi_eh_wakeup() is strictly serialized, when scsi_eh_wakeup() is called
for the last in-flight request, scsi_host_busy() has been run for (N * M -
1) times, and request has been iterated for (N*M - 1) * (N * M) times.

If both N and M are big enough, hard lockup can be triggered on acquiring
host lock, and it is observed on mpi3mr(128 hw queues, queue depth 8169).

Fix the issue by calling scsi_host_busy() outside the host lock. We don't
need the host lock for getting busy count because host the lock never
covers that.

[mkp: Drop unnecessary 'busy' variables pointed out by Bart]

Cc: Ewan Milne <emilne@redhat.com>
Fixes: 6eb045e092ef ("scsi: core: avoid host-wide host_busy counter for scsi_mq")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20240112070000.4161982-1-ming.lei@redhat.com
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Reviewed-by: Sathya Prakash Veerichetty <safhya.prakash@broadcom.com>
Tested-by: Sathya Prakash Veerichetty <safhya.prakash@broadcom.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/scsi/scsi_error.c | 8 ++++----
drivers/scsi/scsi_lib.c | 2 +-
drivers/scsi/scsi_priv.h | 2 +-
3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 9a289d6f2e5e..66290961c47c 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -61,11 +61,11 @@ static int scsi_eh_try_stu(struct scsi_cmnd *scmd);
static enum scsi_disposition scsi_try_to_abort_cmd(struct scsi_host_template *,
struct scsi_cmnd *);

-void scsi_eh_wakeup(struct Scsi_Host *shost)
+void scsi_eh_wakeup(struct Scsi_Host *shost, unsigned int busy)
{
lockdep_assert_held(shost->host_lock);

- if (scsi_host_busy(shost) == shost->host_failed) {
+ if (busy == shost->host_failed) {
trace_scsi_eh_wakeup(shost);
wake_up_process(shost->ehandler);
SCSI_LOG_ERROR_RECOVERY(5, shost_printk(KERN_INFO, shost,
@@ -88,7 +88,7 @@ void scsi_schedule_eh(struct Scsi_Host *shost)
if (scsi_host_set_state(shost, SHOST_RECOVERY) == 0 ||
scsi_host_set_state(shost, SHOST_CANCEL_RECOVERY) == 0) {
shost->host_eh_scheduled++;
- scsi_eh_wakeup(shost);
+ scsi_eh_wakeup(shost, scsi_host_busy(shost));
}

spin_unlock_irqrestore(shost->host_lock, flags);
@@ -281,7 +281,7 @@ static void scsi_eh_inc_host_failed(struct rcu_head *head)

spin_lock_irqsave(shost->host_lock, flags);
shost->host_failed++;
- scsi_eh_wakeup(shost);
+ scsi_eh_wakeup(shost, scsi_host_busy(shost));
spin_unlock_irqrestore(shost->host_lock, flags);
}

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index d25e1c247253..0e7e9f1e5a02 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -282,7 +282,7 @@ static void scsi_dec_host_busy(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
if (unlikely(scsi_host_in_recovery(shost))) {
spin_lock_irqsave(shost->host_lock, flags);
if (shost->host_failed || shost->host_eh_scheduled)
- scsi_eh_wakeup(shost);
+ scsi_eh_wakeup(shost, scsi_host_busy(shost));
spin_unlock_irqrestore(shost->host_lock, flags);
}
rcu_read_unlock();
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index b14545acb40f..9b5fb30e684b 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -86,7 +86,7 @@ extern void scmd_eh_abort_handler(struct work_struct *work);
extern enum blk_eh_timer_return scsi_timeout(struct request *req);
extern int scsi_error_handler(void *host);
extern enum scsi_disposition scsi_decide_disposition(struct scsi_cmnd *cmd);
-extern void scsi_eh_wakeup(struct Scsi_Host *shost);
+extern void scsi_eh_wakeup(struct Scsi_Host *shost, unsigned int busy);
extern void scsi_eh_scmd_add(struct scsi_cmnd *);
void scsi_eh_ready_devs(struct Scsi_Host *shost,
struct list_head *work_q,
--
2.43.0