vm_page_wire_mapped: explain why failure does not affect correctness
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Authored by kib on Oct 30 2019, 4:10 PM.

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alc
markj

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rS354194: vm_page_wire_mapped: explain why failure does not affect correctness.

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rS FreeBSD src repository - subversion

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kib created this revision.Oct 30 2019, 4:10 PM

Herald added a subscriber: imp. · View Herald TranscriptOct 30 2019, 4:10 PM

Harbormaster completed remote builds in B27281: Diff 63801.Oct 30 2019, 4:10 PM

Was there some specific problem that motivated the change?

Note that the pmap_extract_and_hold() caller may not fall back to the slow path in some cases, e.g., if VM_PROT_QUICK_NOFAULT is specified.

sys/vm/vm_page.c
3766 ↗	(On Diff #63801)	I think the first comma is unnecessary.

This revision is now accepted and ready to land.Oct 30 2019, 4:36 PM

In D22196#485037, @markj wrote:

Was there some specific problem that motivated the change?

Only that I re-read some code and had to trace the path to convince myself once again that it is fine.

Note that the pmap_extract_and_hold() caller may not fall back to the slow path in some cases, e.g., if VM_PROT_QUICK_NOFAULT is specified.

I do not agree. VM_PROT_QUICK_NOFAULT only makes vm_fault_quick...() to not ignore TDP_NOFAULTING. In this case, the code that set TDP_NOFAULTING typically has to handle EFAULT by some means, which is to call vm_fault() explicitly. This is how vn_io_fault() works.

Closed by commit rS354194: vm_page_wire_mapped: explain why failure does not affect correctness. (authored by kib). · Explain WhyOct 30 2019, 5:33 PM

This revision was automatically updated to reflect the committed changes.

kib added a commit: rS354194: vm_page_wire_mapped: explain why failure does not affect correctness..