When a device is deleted through sysfs handle "delete", the code
locks shost->scan_mutex. If multiple devices are deleted at the
same time, these deletes will be handled in series.
On the other hand, sd_shutdown() sometimes issues long latency
commands: sync cache and start_stop. It is not necessary for these
commands to run in series.
To reduce latency of parallel "delete" requests, this patch unlock
shost->scan_mutex before long latency commands and relock the mutex
after the command.
Fixed bug from previous version.
Reported-by: kernel test robot <fengguang.wu@xxxxxxxxx>
Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
drivers/scsi/sd.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 9e0783b..14c5815 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -3304,6 +3304,9 @@ static int sd_start_stop_device(struct scsi_disk *sdkp, int start)
static void sd_shutdown(struct device *dev)
{
struct scsi_disk *sdkp = dev_get_drvdata(dev);
+ struct scsi_device *sdev;
+ struct Scsi_Host *shost;
+ int try_lock_scan_mutex;
if (!sdkp)
return; /* this can happen */
@@ -3311,15 +3314,26 @@ static void sd_shutdown(struct device *dev)
if (pm_runtime_suspended(dev))
return;
+ sdev = sdkp->device;
+ shost = sdev->host;
+ try_lock_scan_mutex = mutex_trylock(&shost->scan_mutex);
+
if (sdkp->WCE && sdkp->media_present) {
+ mutex_unlock(&shost->scan_mutex);
sd_printk(KERN_NOTICE, sdkp, "Synchronizing SCSI cache\n");
sd_sync_cache(sdkp);
+ mutex_lock(&shost->scan_mutex);
}
if (system_state != SYSTEM_RESTART && sdkp->device->manage_start_stop) {
+ mutex_unlock(&shost->scan_mutex);
sd_printk(KERN_NOTICE, sdkp, "Stopping disk\n");
sd_start_stop_device(sdkp, 0);
+ mutex_lock(&shost->scan_mutex);
}
+
+ if (try_lock_scan_mutex)
+ mutex_unlock(&shost->scan_mutex);
}
static int sd_suspend_common(struct device *dev, bool ignore_stop_errors)
--
2.9.3
