Remove some lingering page lock usages.
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Authored by markj on Jan 20 2020, 1:32 PM.

Details

Reviewers

alc
kib
dougm
jeff

Commits

rS357374: Remove a couple of lingering usages of the page lock.

Summary

I neglected to remove vm_page_change_lock(), which still had a couple of
consumers in the contig reclaim code.

Fix object locking. The page lock no longer protects the page's
<object, pindex> tuple as of r352110. Instead we must unconditionally
acquire the object lock and validate the page's object pointer.

Remove an unnecessary second check for page wirings in
vm_page_scan_contig(). Both checks are racy so it doesn't really make
sense to repeat them. Races are handled properly in
vm_page_reclaim_run().

Test Plan

Peter tested the patch.

Diff Detail

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Unit

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Build Status

Buildable 28786
Build 26795: arc lint + arc unit

Event Timeline

markj created this revision.Jan 20 2020, 1:32 PM

Harbormaster completed remote builds in B28786: Diff 67045.Jan 20 2020, 1:32 PM

markj edited the test plan for this revision. (Show Details)Jan 20 2020, 1:32 PM

markj added reviewers: alc, kib, dougm, jeff.

kib accepted this revision.Jan 20 2020, 4:00 PM

kib added inline comments.

sys/vm/vm_page.c
2544	Why don't you relock the right object, instead of giving up ?

This revision is now accepted and ready to land.Jan 20 2020, 4:00 PM

jeff accepted this revision.Jan 21 2020, 6:28 PM

Retry in vm_page_scan_contig() if the object pointer changed.

This revision now requires review to proceed.Jan 23 2020, 5:11 PM

Harbormaster completed remote builds in B28879: Diff 67216.Jan 23 2020, 5:11 PM

jeff added inline comments.Jan 24 2020, 1:55 AM

sys/vm/vm_page.c
2559	I didn't notice this before. What happened to the wired check?
2676	If you trybusy first you can be sure the object is either identical or NULL. I am likely to make this change eventually.

markj added inline comments.Jan 24 2020, 3:35 PM

sys/vm/vm_page.c
2559	There were two wired checks in this function, I removed one. There is no purpose to having two checks, since there's nothing preventing a wiring from appearing after this function returns and before the reclamation begins. vm_page_reclaim_contig() handles such races.