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linux/drivers/scsi/scsi_pm.c
Bart Van Assche 21e6ba3f0e 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 domains 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 ef0ff68351 ("driver core: Probe devices
asynchronously instead of the driver") that went upstream in kernel version
v5.1-rc1.

Cc: Lee Duncan <lduncan@suse.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
2019-03-27 21:03:58 -04:00

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/*
* scsi_pm.c Copyright (C) 2010 Alan Stern
*
* SCSI dynamic Power Management
* Initial version: Alan Stern <stern@rowland.harvard.edu>
*/
#include <linux/pm_runtime.h>
#include <linux/export.h>
#include <linux/async.h>
#include <linux/blk-pm.h>
#include <scsi/scsi.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_driver.h>
#include <scsi/scsi_host.h>
#include "scsi_priv.h"
#ifdef CONFIG_PM_SLEEP
static int do_scsi_suspend(struct device *dev, const struct dev_pm_ops *pm)
{
return pm && pm->suspend ? pm->suspend(dev) : 0;
}
static int do_scsi_freeze(struct device *dev, const struct dev_pm_ops *pm)
{
return pm && pm->freeze ? pm->freeze(dev) : 0;
}
static int do_scsi_poweroff(struct device *dev, const struct dev_pm_ops *pm)
{
return pm && pm->poweroff ? pm->poweroff(dev) : 0;
}
static int do_scsi_resume(struct device *dev, const struct dev_pm_ops *pm)
{
return pm && pm->resume ? pm->resume(dev) : 0;
}
static int do_scsi_thaw(struct device *dev, const struct dev_pm_ops *pm)
{
return pm && pm->thaw ? pm->thaw(dev) : 0;
}
static int do_scsi_restore(struct device *dev, const struct dev_pm_ops *pm)
{
return pm && pm->restore ? pm->restore(dev) : 0;
}
static int scsi_dev_type_suspend(struct device *dev,
int (*cb)(struct device *, const struct dev_pm_ops *))
{
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
int err;
err = scsi_device_quiesce(to_scsi_device(dev));
if (err == 0) {
err = cb(dev, pm);
if (err)
scsi_device_resume(to_scsi_device(dev));
}
dev_dbg(dev, "scsi suspend: %d\n", err);
return err;
}
static int scsi_dev_type_resume(struct device *dev,
int (*cb)(struct device *, const struct dev_pm_ops *))
{
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
int err = 0;
err = cb(dev, pm);
scsi_device_resume(to_scsi_device(dev));
dev_dbg(dev, "scsi resume: %d\n", err);
if (err == 0) {
pm_runtime_disable(dev);
err = pm_runtime_set_active(dev);
pm_runtime_enable(dev);
/*
* Forcibly set runtime PM status of request queue to "active"
* to make sure we can again get requests from the queue
* (see also blk_pm_peek_request()).
*
* The resume hook will correct runtime PM status of the disk.
*/
if (!err && scsi_is_sdev_device(dev)) {
struct scsi_device *sdev = to_scsi_device(dev);
if (sdev->request_queue->dev)
blk_set_runtime_active(sdev->request_queue);
}
}
return err;
}
static int
scsi_bus_suspend_common(struct device *dev,
int (*cb)(struct device *, const struct dev_pm_ops *))
{
int err = 0;
if (scsi_is_sdev_device(dev)) {
/*
* All the high-level SCSI drivers that implement runtime
* PM treat runtime suspend, system suspend, and system
* hibernate nearly identically. In all cases the requirements
* for runtime suspension are stricter.
*/
if (pm_runtime_suspended(dev))
return 0;
err = scsi_dev_type_suspend(dev, cb);
}
return err;
}
static void async_sdev_resume(void *dev, async_cookie_t cookie)
{
scsi_dev_type_resume(dev, do_scsi_resume);
}
static void async_sdev_thaw(void *dev, async_cookie_t cookie)
{
scsi_dev_type_resume(dev, do_scsi_thaw);
}
static void async_sdev_restore(void *dev, async_cookie_t cookie)
{
scsi_dev_type_resume(dev, do_scsi_restore);
}
static int scsi_bus_resume_common(struct device *dev,
int (*cb)(struct device *, const struct dev_pm_ops *))
{
async_func_t fn;
if (!scsi_is_sdev_device(dev))
fn = NULL;
else if (cb == do_scsi_resume)
fn = async_sdev_resume;
else if (cb == do_scsi_thaw)
fn = async_sdev_thaw;
else if (cb == do_scsi_restore)
fn = async_sdev_restore;
else
fn = NULL;
if (!fn) {
pm_runtime_disable(dev);
pm_runtime_set_active(dev);
pm_runtime_enable(dev);
}
return 0;
}
static int scsi_bus_prepare(struct device *dev)
{
if (scsi_is_host_device(dev)) {
/* Wait until async scanning is finished */
scsi_complete_async_scans();
}
return 0;
}
static int scsi_bus_suspend(struct device *dev)
{
return scsi_bus_suspend_common(dev, do_scsi_suspend);
}
static int scsi_bus_resume(struct device *dev)
{
return scsi_bus_resume_common(dev, do_scsi_resume);
}
static int scsi_bus_freeze(struct device *dev)
{
return scsi_bus_suspend_common(dev, do_scsi_freeze);
}
static int scsi_bus_thaw(struct device *dev)
{
return scsi_bus_resume_common(dev, do_scsi_thaw);
}
static int scsi_bus_poweroff(struct device *dev)
{
return scsi_bus_suspend_common(dev, do_scsi_poweroff);
}
static int scsi_bus_restore(struct device *dev)
{
return scsi_bus_resume_common(dev, do_scsi_restore);
}
#else /* CONFIG_PM_SLEEP */
#define scsi_bus_prepare NULL
#define scsi_bus_suspend NULL
#define scsi_bus_resume NULL
#define scsi_bus_freeze NULL
#define scsi_bus_thaw NULL
#define scsi_bus_poweroff NULL
#define scsi_bus_restore NULL
#endif /* CONFIG_PM_SLEEP */
static int sdev_runtime_suspend(struct device *dev)
{
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
struct scsi_device *sdev = to_scsi_device(dev);
int err = 0;
err = blk_pre_runtime_suspend(sdev->request_queue);
if (err)
return err;
if (pm && pm->runtime_suspend)
err = pm->runtime_suspend(dev);
blk_post_runtime_suspend(sdev->request_queue, err);
return err;
}
static int scsi_runtime_suspend(struct device *dev)
{
int err = 0;
dev_dbg(dev, "scsi_runtime_suspend\n");
if (scsi_is_sdev_device(dev))
err = sdev_runtime_suspend(dev);
/* Insert hooks here for targets, hosts, and transport classes */
return err;
}
static int sdev_runtime_resume(struct device *dev)
{
struct scsi_device *sdev = to_scsi_device(dev);
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
int err = 0;
blk_pre_runtime_resume(sdev->request_queue);
if (pm && pm->runtime_resume)
err = pm->runtime_resume(dev);
blk_post_runtime_resume(sdev->request_queue, err);
return err;
}
static int scsi_runtime_resume(struct device *dev)
{
int err = 0;
dev_dbg(dev, "scsi_runtime_resume\n");
if (scsi_is_sdev_device(dev))
err = sdev_runtime_resume(dev);
/* Insert hooks here for targets, hosts, and transport classes */
return err;
}
static int scsi_runtime_idle(struct device *dev)
{
dev_dbg(dev, "scsi_runtime_idle\n");
/* Insert hooks here for targets, hosts, and transport classes */
if (scsi_is_sdev_device(dev)) {
pm_runtime_mark_last_busy(dev);
pm_runtime_autosuspend(dev);
return -EBUSY;
}
return 0;
}
int scsi_autopm_get_device(struct scsi_device *sdev)
{
int err;
err = pm_runtime_get_sync(&sdev->sdev_gendev);
if (err < 0 && err !=-EACCES)
pm_runtime_put_sync(&sdev->sdev_gendev);
else
err = 0;
return err;
}
EXPORT_SYMBOL_GPL(scsi_autopm_get_device);
void scsi_autopm_put_device(struct scsi_device *sdev)
{
pm_runtime_put_sync(&sdev->sdev_gendev);
}
EXPORT_SYMBOL_GPL(scsi_autopm_put_device);
void scsi_autopm_get_target(struct scsi_target *starget)
{
pm_runtime_get_sync(&starget->dev);
}
void scsi_autopm_put_target(struct scsi_target *starget)
{
pm_runtime_put_sync(&starget->dev);
}
int scsi_autopm_get_host(struct Scsi_Host *shost)
{
int err;
err = pm_runtime_get_sync(&shost->shost_gendev);
if (err < 0 && err !=-EACCES)
pm_runtime_put_sync(&shost->shost_gendev);
else
err = 0;
return err;
}
void scsi_autopm_put_host(struct Scsi_Host *shost)
{
pm_runtime_put_sync(&shost->shost_gendev);
}
const struct dev_pm_ops scsi_bus_pm_ops = {
.prepare = scsi_bus_prepare,
.suspend = scsi_bus_suspend,
.resume = scsi_bus_resume,
.freeze = scsi_bus_freeze,
.thaw = scsi_bus_thaw,
.poweroff = scsi_bus_poweroff,
.restore = scsi_bus_restore,
.runtime_suspend = scsi_runtime_suspend,
.runtime_resume = scsi_runtime_resume,
.runtime_idle = scsi_runtime_idle,
};
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