On Sun, 2014-03-16 at 11:21 -0700, James Bottomley wrote:
> On Sat, 2014-03-15 at 16:35 -0700, Dan Williams wrote:
> > On Sat, Mar 15, 2014 at 2:47 PM, James Bottomley
> > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > > On Fri, 2014-03-14 at 13:11 -0700, Dan Williams wrote:
> > >> On Mon, Mar 10, 2014 at 11:29 PM, James Bottomley
> > >> <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > >> >> > In the long game, though this whole debate is moot: setups with hard
> > >> >> > wired start times adhere to them regardless of what the system does, so
> > >> >> > they ignore start unit commands. Systems without hard wired start times
> > >> >> > can usually be started at once, so us introducing a delay is unnecessary
> > >> >> > in either case.
> > >> >>
> > >> >> Ok, then I'll let the patch stand as is.
> > >> >
> > >> > Sounds good.
> > >> >
> > >> > James
> > >> >
> > >> >
> > >>
> > >> Well, one more chirp about this. If the user has disabled async
> > >> scanning by CONFIG_SCSI_SCAN_ASYNC=n or scsi_mod.scan != "async" then
> > >> resume should follow suit. I'll include this in the next rev.
> > >
> > > Hm, OK, if this is tied at the hip to async scanning, why do you need
> > > another async domain for it? Why not just use the current async
> > > scanning domain ... it will actually probably resolve a few nasty (but
> > > wholly manufactured) races where scanning races with suspend.
> >
> > I considered that initially, but it ends up destroying most/all of the
> > benefit of doing it asynchronously. This is due to the fact that
> > scsi_sd_probe_domain is flushed by the async_synchronize_full()
> > performed in dpm_resume(). We want userspace to resume while the disk
> > may still be starting.
>
> OK, finally got it, the new domain doesn't participate in
> async_synchronize_full() but scsi_sd_probe_domain does (and has to
> because of the device and module operations). That might actually be
> worth a comment somewhere.
Fair enough, see the comment added to the declaration of
scsi_sd_pm_domain below.
BTW, these patches are independent. Patch 1 and 2 can go through
Tejun/libata and this one can go through you/scsi by itself.
8<----------
Subject: scsi: async sd resume
From: Dan Williams <dan.j.williams@xxxxxxxxx>
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@xxxxxxxxx>
Cc: Phillip Susi <psusi@xxxxxxxxxx>
[alan: bug fix and clean up suggestion]
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Suggested-by: Todd Brandt <todd.e.brandt@xxxxxxxxxxxxxxx>
[djbw: kick all resume work to the async queue]
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/scsi/Kconfig | 3 +
drivers/scsi/scsi.c | 9 +++
drivers/scsi/scsi_pm.c | 128 ++++++++++++++++++++++++++++++++++++----------
drivers/scsi/scsi_priv.h | 2 +
drivers/scsi/scsi_scan.c | 2 -
drivers/scsi/sd.c | 1
6 files changed, 115 insertions(+), 30 deletions(-)
diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index c8bd092fc945..02832d64d918 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -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
diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index d8afec8317cf..1b345bf41a91 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -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
diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
index 001e9ceda4c3..7454498c4091 100644
--- a/drivers/scsi/scsi_pm.c
+++ b/drivers/scsi/scsi_pm.c
@@ -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 */
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index f079a598bed4..48e5b657e79f 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -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;
/*
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 307a81137607..6b2f51f52af6 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -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");
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 470954aba728..700c595c603e 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -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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