Commit 3c31b52f authored by Dan Williams's avatar Dan Williams
Browse files

scsi: async sd resume

async_schedule() sd resume work to allow disks and other devices to
resume in parallel.

This moves the entirety of scsi_device resume to an async context to
ensure that scsi_device_resume() remains ordered with respect to the
completion of the start/stop command.  For the duration of the resume,
new command submissions (that do not originate from the scsi-core) will
be deferred (BLKPREP_DEFER).

It adds a new ASYNC_DOMAIN_EXCLUSIVE(scsi_sd_pm_domain) as a container
of these operations.  Like scsi_sd_probe_domain it is flushed at
sd_remove() time to ensure async ops do not continue past the
end-of-life of the sdev.  The implementation explicitly refrains from
reusing scsi_sd_probe_domain directly for this purpose as it is flushed
at the end of dpm_resume(), potentially defeating some of the benefit.
Given sdevs are quiesced it is permissible for these resume operations
to bleed past the async_synchronize_full() calls made by the driver
core.

We defer the resolution of which pm callback to call until
scsi_dev_type_{suspend|resume} time and guarantee that the callback
parameter is never NULL.  With this in place the type of resume
operation is encoded in the async function identifier.

There is a concern that async resume could trigger PSU overload.  In the
enterprise, storage enclosures enforce staggered spin-up regardless of
what the kernel does making async scanning safe by default.  Outside of
that context a user can disable asynchronous scanning via a kernel
command line or CONFIG_SCSI_SCAN_ASYNC.  Honor that setting when
deciding whether to do resume asynchronously.

Inspired by Todd's analysis and initial proposal [2]:
https://01.org/suspendresume/blogs/tebrandt/2013/hard-disk-resume-optimization-simpler-approach



Cc: Len Brown <len.brown@intel.com>
Cc: Phillip Susi <psusi@ubuntu.com>
[alan: bug fix and clean up suggestion]
Acked-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Suggested-by: default avatarTodd Brandt <todd.e.brandt@linux.intel.com>
[djbw: kick all resume work to the async queue]
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 455c6fdb
......@@ -263,6 +263,9 @@ config SCSI_SCAN_ASYNC
You can override this choice by specifying "scsi_mod.scan=sync"
or async on the kernel's command line.
Note that this setting also affects whether resuming from
system suspend will be performed asynchronously.
menu "SCSI Transports"
depends on SCSI
......
......@@ -91,6 +91,15 @@ EXPORT_SYMBOL(scsi_logging_level);
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()
*/
ASYNC_DOMAIN_EXCLUSIVE(scsi_sd_pm_domain);
EXPORT_SYMBOL(scsi_sd_pm_domain);
/* NB: These are exposed through /proc/scsi/scsi and form part of the ABI.
* You may not alter any existing entry (although adding new ones is
* encouraged once assigned by ANSI/INCITS T10
......
......@@ -18,35 +18,77 @@
#ifdef CONFIG_PM_SLEEP
static int scsi_dev_type_suspend(struct device *dev, int (*cb)(struct device *))
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;
/* flush pending in-flight resume operations, suspend is synchronous */
async_synchronize_full_domain(&scsi_sd_pm_domain);
err = scsi_device_quiesce(to_scsi_device(dev));
if (err == 0) {
if (cb) {
err = cb(dev);
if (err)
scsi_device_resume(to_scsi_device(dev));
}
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 *))
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;
if (cb)
err = cb(dev);
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);
pm_runtime_set_active(dev);
pm_runtime_enable(dev);
}
return err;
}
static int
scsi_bus_suspend_common(struct device *dev, int (*cb)(struct device *))
scsi_bus_suspend_common(struct device *dev,
int (*cb)(struct device *, const struct dev_pm_ops *))
{
int err = 0;
......@@ -66,20 +108,54 @@ scsi_bus_suspend_common(struct device *dev, int (*cb)(struct device *))
return err;
}
static int
scsi_bus_resume_common(struct device *dev, int (*cb)(struct device *))
static void async_sdev_resume(void *dev, async_cookie_t cookie)
{
int err = 0;
scsi_dev_type_resume(dev, do_scsi_resume);
}
if (scsi_is_sdev_device(dev))
err = scsi_dev_type_resume(dev, cb);
static void async_sdev_thaw(void *dev, async_cookie_t cookie)
{
scsi_dev_type_resume(dev, do_scsi_thaw);
}
if (err == 0) {
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) {
async_schedule_domain(fn, dev, &scsi_sd_pm_domain);
/*
* If a user has disabled async probing a likely reason
* is due to a storage enclosure that does not inject
* staggered spin-ups. For safety, make resume
* synchronous as well in that case.
*/
if (strncmp(scsi_scan_type, "async", 5) != 0)
async_synchronize_full_domain(&scsi_sd_pm_domain);
} else {
pm_runtime_disable(dev);
pm_runtime_set_active(dev);
pm_runtime_enable(dev);
}
return err;
return 0;
}
static int scsi_bus_prepare(struct device *dev)
......@@ -97,38 +173,32 @@ static int scsi_bus_prepare(struct device *dev)
static int scsi_bus_suspend(struct device *dev)
{
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
return scsi_bus_suspend_common(dev, pm ? pm->suspend : NULL);
return scsi_bus_suspend_common(dev, do_scsi_suspend);
}
static int scsi_bus_resume(struct device *dev)
{
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
return scsi_bus_resume_common(dev, pm ? pm->resume : NULL);
return scsi_bus_resume_common(dev, do_scsi_resume);
}
static int scsi_bus_freeze(struct device *dev)
{
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
return scsi_bus_suspend_common(dev, pm ? pm->freeze : NULL);
return scsi_bus_suspend_common(dev, do_scsi_freeze);
}
static int scsi_bus_thaw(struct device *dev)
{
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
return scsi_bus_resume_common(dev, pm ? pm->thaw : NULL);
return scsi_bus_resume_common(dev, do_scsi_thaw);
}
static int scsi_bus_poweroff(struct device *dev)
{
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
return scsi_bus_suspend_common(dev, pm ? pm->poweroff : NULL);
return scsi_bus_suspend_common(dev, do_scsi_poweroff);
}
static int scsi_bus_restore(struct device *dev)
{
const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
return scsi_bus_resume_common(dev, pm ? pm->restore : NULL);
return scsi_bus_resume_common(dev, do_scsi_restore);
}
#else /* CONFIG_PM_SLEEP */
......
......@@ -112,6 +112,7 @@ extern void scsi_exit_procfs(void);
#endif /* CONFIG_PROC_FS */
/* scsi_scan.c */
extern char scsi_scan_type[];
extern int scsi_complete_async_scans(void);
extern int scsi_scan_host_selected(struct Scsi_Host *, unsigned int,
unsigned int, unsigned int, int);
......@@ -166,6 +167,7 @@ static inline int scsi_autopm_get_host(struct Scsi_Host *h) { return 0; }
static inline void scsi_autopm_put_host(struct Scsi_Host *h) {}
#endif /* CONFIG_PM_RUNTIME */
extern struct async_domain scsi_sd_pm_domain;
extern struct async_domain scsi_sd_probe_domain;
/*
......
......@@ -97,7 +97,7 @@ MODULE_PARM_DESC(max_luns,
#define SCSI_SCAN_TYPE_DEFAULT "sync"
#endif
static char scsi_scan_type[6] = SCSI_SCAN_TYPE_DEFAULT;
char scsi_scan_type[6] = SCSI_SCAN_TYPE_DEFAULT;
module_param_string(scan, scsi_scan_type, sizeof(scsi_scan_type), S_IRUGO);
MODULE_PARM_DESC(scan, "sync, async or none");
......
......@@ -3020,6 +3020,7 @@ static int sd_remove(struct device *dev)
devt = disk_devt(sdkp->disk);
scsi_autopm_get_device(sdkp->device);
async_synchronize_full_domain(&scsi_sd_pm_domain);
async_synchronize_full_domain(&scsi_sd_probe_domain);
blk_queue_prep_rq(sdkp->device->request_queue, scsi_prep_fn);
blk_queue_unprep_rq(sdkp->device->request_queue, NULL);
......
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