From f049cf1a7b6737c75884247c3f6383ef104d255a Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 30 Apr 2019 14:39:18 -0700 Subject: scsi: sd: Rely on the driver core for asynchronous probing As explained during the 2018 LSF/MM session about increasing SCSI disk probing concurrency, the problems with the current probing approach are as follows: - The driver core is unaware of asynchronous SCSI LUN probing. wait_for_device_probe() waits for all asynchronous probes except asynchronous SCSI disk probes. - There is unnecessary serialization between sd_probe() and sd_remove(). This can lead to a deadlock. Hence this patch that modifies the sd driver such that it uses the driver core framework for asynchronous probing. The async domain and get_device()/put_device() pairs that became superfluous due to this change are removed. This patch does not affect the time needed for loading the scsi_debug kernel module with parameters delay=0 and max_luns=256. This patch depends on commit ef0ff68351be ("driver core: Probe devices asynchronously instead of the driver") that went upstream in kernel version v5.1-rc1. Cc: Lee Duncan Cc: Hannes Reinecke Cc: Luis Chamberlain Cc: Johannes Thumshirn Cc: Christoph Hellwig Cc: Pavel Machek Cc: Dan Williams Signed-off-by: Bart Van Assche Reviewed-by: Hannes Reinecke Signed-off-by: Martin K. Petersen --- drivers/scsi/sd.c | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-) (limited to 'drivers/scsi/sd.c') diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index f3564e406160..2ba7eef4105a 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -568,6 +568,7 @@ static struct scsi_driver sd_template = { .name = "sd", .owner = THIS_MODULE, .probe = sd_probe, + .probe_type = PROBE_PREFER_ASYNCHRONOUS, .remove = sd_remove, .shutdown = sd_shutdown, .pm = &sd_pm_ops, @@ -3253,12 +3254,8 @@ static int sd_format_disk_name(char *prefix, int index, char *buf, int buflen) return 0; } -/* - * The asynchronous part of sd_probe - */ -static void sd_probe_async(void *data, async_cookie_t cookie) +static void sd_probe_part2(struct scsi_disk *sdkp) { - struct scsi_disk *sdkp = data; struct scsi_device *sdp; struct gendisk *gd; u32 index; @@ -3313,7 +3310,6 @@ static void sd_probe_async(void *data, async_cookie_t cookie) sd_printk(KERN_NOTICE, sdkp, "Attached SCSI %sdisk\n", sdp->removable ? "removable " : ""); scsi_autopm_put_device(sdp); - put_device(&sdkp->dev); } /** @@ -3405,8 +3401,7 @@ static int sd_probe(struct device *dev) get_device(dev); dev_set_drvdata(dev, sdkp); - get_device(&sdkp->dev); /* prevent release before async_schedule */ - async_schedule_domain(sd_probe_async, sdkp, &scsi_sd_probe_domain); + sd_probe_part2(sdkp); return 0; @@ -3442,7 +3437,6 @@ static int sd_remove(struct device *dev) scsi_autopm_get_device(sdkp->device); async_synchronize_full_domain(&scsi_sd_pm_domain); - async_synchronize_full_domain(&scsi_sd_probe_domain); device_del(&sdkp->dev); del_gendisk(sdkp->disk); sd_shutdown(dev); -- cgit v1.2.3