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author | Dan Williams <dan.j.williams@intel.com> | 2014-04-10 15:30:35 -0700 |
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committer | Dan Williams <dan.j.williams@intel.com> | 2014-04-10 15:30:35 -0700 |
commit | 3c31b52f96f7b559d950b16113c0f68c72a1985e (patch) | |
tree | 2ae13004870a1fed2e6f9fee49111fa947cb5d06 /fs | |
parent | 455c6fdbd219161bd09b1165f11699d6d73de11c (diff) | |
download | linux-stable-3c31b52f96f7b559d950b16113c0f68c72a1985e.tar.gz linux-stable-3c31b52f96f7b559d950b16113c0f68c72a1985e.tar.bz2 linux-stable-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 'fs')
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