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| author | Dan Williams <dan.j.williams@intel.com> | 2014-04-11 00:30:35 +0200 |
|---|---|---|
| committer | Dan Williams <dan.j.williams@intel.com> | 2014-04-11 00:30:35 +0200 |
| commit | 3c31b52f96f7b559d950b16113c0f68c72a1985e (patch) | |
| tree | 2ae13004870a1fed2e6f9fee49111fa947cb5d06 /drivers/scsi/scsi_priv.h | |
| parent | Linux 3.14 (diff) | |
| download | linux-3c31b52f96f7b559d950b16113c0f68c72a1985e.tar.xz linux-3c31b52f96f7b559d950b16113c0f68c72a1985e.zip | |
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: Alan Stern <stern@rowland.harvard.edu>
Suggested-by: Todd Brandt <todd.e.brandt@linux.intel.com>
[djbw: kick all resume work to the async queue]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/scsi/scsi_priv.h')
| -rw-r--r-- | drivers/scsi/scsi_priv.h | 2 |
1 files changed, 2 insertions, 0 deletions
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; /* |