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[RFC,v3,2/2] scsi: add rate limit to scsi sense code uevent

Message ID 20170712223535.2609814-3-songliubraving@fb.com (mailing list archive)
State Changes Requested, archived
Headers show

Commit Message

Song Liu July 12, 2017, 10:35 p.m. UTC 
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 <songliubraving@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 mbox

Patch

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