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, some devices do long latency IO during deletion, for example, sd_shutdown() may do sync cache and/or start_stop. It is not necessary for these commands to run in series. To reduce latency of parallel "delete" requests, this patch reduces the protection of scan_mutex. The only function with Scsi_Host called in __scsi_remove_device() is the optional slave_destroy(). Therefore, the protection of scan_mutex is only necessary for this function. Signed-off-by: Song Liu <[email protected]> --- drivers/scsi/scsi_sysfs.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 82dfe07..e7a9e28 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -610,7 +610,7 @@ static int scsi_sdev_check_buf_bit(const char *buf) return 1; else if (buf[0] == '0') return 0; - else + else return -EINVAL; } else return -EINVAL; @@ -774,7 +774,7 @@ store_queue_type_field(struct device *dev, struct device_attribute *attr, if (!sdev->tagged_supported) return -EINVAL; - + sdev_printk(KERN_INFO, sdev, "ignoring write to deprecated queue_type attribute"); return count; @@ -1302,8 +1302,11 @@ void __scsi_remove_device(struct scsi_device *sdev) blk_cleanup_queue(sdev->request_queue); cancel_work_sync(&sdev->requeue_work); - if (sdev->host->hostt->slave_destroy) + if (sdev->host->hostt->slave_destroy) { + mutex_lock(&sdev->host->scan_mutex); sdev->host->hostt->slave_destroy(sdev); + mutex_unlock(&sdev->host->scan_mutex); + } transport_destroy_device(dev); /* @@ -1322,11 +1325,7 @@ void __scsi_remove_device(struct scsi_device *sdev) **/ void scsi_remove_device(struct scsi_device *sdev) { - struct Scsi_Host *shost = sdev->host; - - mutex_lock(&shost->scan_mutex); __scsi_remove_device(sdev); - mutex_unlock(&shost->scan_mutex); } EXPORT_SYMBOL(scsi_remove_device); -- 2.9.3
