Differential D25577

(lookup 2) vfs: add the infrastructure for lockless lookup
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Authored by mjg on Jul 6 2020, 7:29 PM.

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kib
jeff
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rS363518: vfs: add the infrastructure for lockless lookup

Summary

Assorted changes split out from the complete diff. Some have value on their own, but for the most part are only there for the new lookup.

Diff Detail

Repository

rS FreeBSD src repository - subversion

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Event Timeline

mjg created this revision.Jul 6 2020, 7:29 PM

Herald added a subscriber: imp. · View Herald TranscriptJul 6 2020, 7:29 PM

mjg requested review of this revision.Jul 6 2020, 7:29 PM

Harbormaster completed remote builds in B32163: Diff 74129.Jul 6 2020, 7:29 PM

mckusick mentioned this in D25579: (lookup 4) ufs: add support for lockless lookup.Jul 6 2020, 11:02 PM

missing break

kib added inline comments.Jul 11 2020, 11:02 AM

sys/kern/kern_descrip.c
3354 ↗	(On Diff #74149)	I am still surprised with such loops. Don't you need yield sometimes ?
sys/kern/vfs_subr.c
3083 ↗	(On Diff #74149)	Why not extract this block from there and vget_finish() into a common function ?

mjg added inline comments.Jul 11 2020, 12:12 PM

sys/kern/kern_descrip.c
3354 ↗	(On Diff #74149)	If worrying about excessive looping, I think the right solution is to do the above once and in case of failure take the lock.
sys/kern/vfs_subr.c
3083 ↗	(On Diff #74149)	ok, will update later

kib added inline comments.Jul 11 2020, 12:47 PM

sys/kern/kern_descrip.c
3354 ↗	(On Diff #74149)	My concern that if we are on UP and mutator is preempted by this loop at the unlucky moment, system can be livelocked.

rebase

does not address vref_smr yet

Harbormaster completed remote builds in B32269: Diff 74348.Jul 12 2020, 9:25 AM

mjg added inline comments.Jul 12 2020, 9:32 AM

sys/kern/vfs_subr.c
3083 ↗	(On Diff #74149)	So I don't know how to name this. In the patchset I introduce vget_finish_ref later to facilitate WANTPARENT/!LOCKLEAF lookups, but I'm not going to call something like that from vref.

kib added inline comments.Jul 12 2020, 7:02 PM

sys/kern/vfs_subr.c
3083 ↗	(On Diff #74149)	I would call it vref_hold() or vget_ref_hold(). This name describes the action of the code.

add vfs_smr_entered_load
vget_finish_ref

sys/kern/vfs_subr.c
3083 ↗	(On Diff #74149)	I reworked the only consumer of vref_smr to use vget direclty instead, thus getting rid of the problem for the time being.

add vn_load_data_smr

kib accepted this revision.Jul 13 2020, 6:24 PM

This revision is now accepted and ready to land.Jul 13 2020, 6:24 PM

Closed by commit rS363518: vfs: add the infrastructure for lockless lookup (authored by mjg). · Explain WhyJul 25 2020, 10:33 AM

This revision was automatically updated to reflect the committed changes.

mjg added a commit: rS363518: vfs: add the infrastructure for lockless lookup.

Revision Contents
Changeset List

Path

Size

head/

sys/

kern/

29 lines

103 lines

11 lines

security/

mac/

mac_framework.h

3 lines

sys/

1 line

1 line

16 lines

Diff 74908

head/sys/kern/kern_descrip.c

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head/sys/kern/vfs_subr.c

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head/sys/kern/vnode_if.src

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head/sys/security/mac/mac_framework.h

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head/sys/sys/filedesc.h

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head/sys/sys/mount.h

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head/sys/sys/vnode.h

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