This patch adds rate limits to SCSI sense code uevets. Currently,
the rate limit is hard-coded to 64 events per second per Scsi_Host.
The code tracks nano second time of latest 64 events in a circular
buffer. When a new event arrives, the time is compared against the
latest time in the buffer. If the difference is smaller than one
second, the new event is dropped.
Signed-off-by: Song Liu <songliubrav...@fb.com>
---
drivers/scsi/hosts.c | 4 ++++
drivers/scsi/scsi_error.c | 16 ++++++++++++++++
include/scsi/scsi_host.h | 13 +++++++++++++
3 files changed, 33 insertions(+)
diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 831a1c8..219481b 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -408,6 +408,10 @@ struct Scsi_Host *scsi_host_alloc(struct
scsi_host_template *sht, int privsize)
init_waitqueue_head(&shost->host_wait);
mutex_init(&shost->scan_mutex);
+#ifdef CONFIG_SCSI_SENSE_UEVENT
+ spin_lock_init(&shost->latest_event_lock);
+#endif
+
index = ida_simple_get(&host_index_ida, 0, 0, GFP_KERNEL);
if (index < 0)
goto fail_kfree;
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index b8ef869..a0f5aab 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -436,10 +436,26 @@ static void scsi_send_sense_uevent(struct scsi_device
*sdev,
#ifdef CONFIG_SCSI_SENSE_UEVENT
struct scsi_event *evt;
unsigned char sb_len;
+ struct Scsi_Host *shost = sdev->host;
+ unsigned long flags;
+ u64 time_ns;
if (!test_bit(sshdr->sense_key & 0xf,
&sdev->sense_event_filter))
return;
+
+ time_ns = ktime_to_ns(ktime_get());
+ spin_lock_irqsave(&shost->latest_event_lock, flags);
+ if (time_ns - shost->latest_event_times[shost->latest_event_idx] <
+ NSEC_PER_SEC) {
+ spin_unlock_irqrestore(&shost->latest_event_lock, flags);
+ return;
+ }
+ shost->latest_event_times[shost->latest_event_idx] = time_ns;
+ shost->latest_event_idx = (shost->latest_event_idx + 1) %
+ MAX_SENSE_EVENT_PER_SECOND;
+ spin_unlock_irqrestore(&shost->latest_event_lock, flags);
+
evt = sdev_evt_alloc(SDEV_EVT_SCSI_SENSE, GFP_ATOMIC);
if (!evt)
return;
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index afb0481..8aacb15 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -731,6 +731,19 @@ struct Scsi_Host {
*/
struct device *dma_dev;
+#ifdef CONFIG_SCSI_SENSE_UEVENT
+#define MAX_SENSE_EVENT_PER_SECOND 64
+ /*
+ * To rate limit uevents to MAX_SENSE_EVENT_PER_SECOND, we track
+ * nano second time of MAX_SENSE_EVENT_PER_SECOND most recent
+ * events. If there are already MAX_SENSE_EVENT_PER_SECOND in the
+ * past seconds, new event is dropped.
+ */
+ u64 latest_event_times[MAX_SENSE_EVENT_PER_SECOND];
+ int latest_event_idx;
+ spinlock_t latest_event_lock;
+#endif
+
/*
* We should ensure that this is aligned, both for better performance
* and also because some compilers (m68k) don't automatically force
--
2.9.3
