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 <lduncan@xxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Cc: Johannes Thumshirn <jthumshirn@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Pavel Machek <pavel@xxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
drivers/scsi/scsi.c | 12 +++---------
drivers/scsi/scsi_pm.c | 6 +-----
drivers/scsi/scsi_priv.h | 1 -
drivers/scsi/sd.c | 12 +++---------
4 files changed, 7 insertions(+), 24 deletions(-)
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 99a7b9f520ae..f5cd632606cf 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -85,15 +85,10 @@ unsigned int scsi_logging_level;
EXPORT_SYMBOL(scsi_logging_level);
#endif
-/* sd, scsi core and power management need to coordinate flushing async actions */
-ASYNC_DOMAIN(scsi_sd_probe_domain);
-EXPORT_SYMBOL(scsi_sd_probe_domain);
-
/*
- * Separate domain (from scsi_sd_probe_domain) to maximize the benefit of
- * asynchronous system resume operations. It is marked 'exclusive' to avoid
- * being included in the async_synchronize_full() that is invoked by
- * dpm_resume()
+ * Domain for asynchronous system resume operations. It is marked 'exclusive'
+ * to avoid being included in the async_synchronize_full() that is invoked by
+ * dpm_resume().
*/
ASYNC_DOMAIN_EXCLUSIVE(scsi_sd_pm_domain);
EXPORT_SYMBOL(scsi_sd_pm_domain);
@@ -820,7 +815,6 @@ static void __exit exit_scsi(void)
scsi_exit_devinfo();
scsi_exit_procfs();
scsi_exit_queue();
- async_unregister_domain(&scsi_sd_probe_domain);
}
subsys_initcall(init_scsi);
diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
index 7639df91b110..bc8c72a6356d 100644
--- a/drivers/scsi/scsi_pm.c
+++ b/drivers/scsi/scsi_pm.c
@@ -175,11 +175,7 @@ static int scsi_bus_resume_common(struct device *dev,
static int scsi_bus_prepare(struct device *dev)
{
- if (scsi_is_sdev_device(dev)) {
- /* sd probing uses async_schedule. Wait until it finishes. */
- async_synchronize_full_domain(&scsi_sd_probe_domain);
-
- } else if (scsi_is_host_device(dev)) {
+ if (scsi_is_host_device(dev)) {
/* Wait until async scanning is finished */
scsi_complete_async_scans();
}
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index 5f21547b2ad2..cc2859d76d81 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -175,7 +175,6 @@ static inline void scsi_autopm_put_host(struct Scsi_Host *h) {}
#endif /* CONFIG_PM */
extern struct async_domain scsi_sd_pm_domain;
-extern struct async_domain scsi_sd_probe_domain;
/* scsi_dh.c */
#ifdef CONFIG_SCSI_DH
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 2b2bc4b49d78..ae6634885afe 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -567,6 +567,7 @@ 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,
@@ -3284,12 +3285,8 @@ 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;
@@ -3343,7 +3340,6 @@ 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);
}
/**
@@ -3435,8 +3431,7 @@ 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;
@@ -3472,7 +3467,6 @@ 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);
--
2.21.0.196.g041f5ea1cf98
