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Differential D18496

add a knob that disables detection of write protected disks
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Authored by avg on Dec 10 2018, 8:21 AM.
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imp
scottl
ken
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rS342169: add a knob that disables detection of write protected disks
Summary

It has been reported that on some systems (with real hardware passed
through to a virtual machine) the WP detection causes USB disk probing
failures.

Test Plan

Tested disk probing with WP detection on and off.

Diff Detail

Repository
rS FreeBSD src repository - subversion
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Build Status
Buildable 21471
Build 20789: arc lint + arc unit

Event Timeline

avg created this revision.Dec 10 2018, 8:21 AM
Harbormaster completed remote builds in B21471: Diff 51799.Dec 10 2018, 8:21 AM
avg added a comment.Dec 10 2018, 8:23 AM

While here, I also fixed setting of the next state in the case of malloc failure in DA_STATE_PROBE_WP.

avg updated this revision to Diff 51800.Dec 10 2018, 8:26 AM

correct description of the new sysctl

Harbormaster completed remote builds in B21472: Diff 51800.Dec 10 2018, 8:26 AM
imp added inline comments.Dec 10 2018, 5:50 PM
sys/cam/scsi/scsi_da.c
3342

wouldn't it be better to go directly to PROBE_RC* rather than have this useless trip through STATE_PROBE_WP?

avg marked 2 inline comments as done.Dec 15 2018, 1:59 PM
avg added inline comments.
sys/cam/scsi/scsi_da.c
3342

That's certainly another possibility to do it, but I am not sure if it's really better.
With respect to run-time execution the difference is negligible, in my opinion.
With respect to code organization da_disable_wp_detection would have to be checked in two places, daregister and dareprobe, instead of one. But that's a pretty minor difference as well.

So, I don't have a preference. I did it this way, but I can re-do it the other way.

3346

I wonder if there should be an inline function for choosing between DA_STATE_PROBE_RC16 and DA_STATE_PROBE_RC, given that the check is going to be repeated 3 or 4 times.

This revision was not accepted when it landed; it landed in state Needs Review.Dec 17 2018, 4:01 PM
Closed by commit rS342169: add a knob that disables detection of write protected disks (authored by avg). · Explain Why
This revision was automatically updated to reflect the committed changes.

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sys/
cam/
scsi/
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Diff 51799

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sys/cam/scsi/scsi_da.c

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