Fix interaction between largepages and seals/writes.
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Authored by kib on Sep 10 2020, 4:48 PM.

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Reviewers

kevans
markj

Commits

rS365613: Fix interaction between largepages and seals/writes.

Summary

On write with SHM_GROW_ON_WRITE, use proper truncate.
Do not allow to grow largepage shm if F_SEAL_GROW is set. Note that shrinks are not supported at all due to unmanaged mappings.
Call to vm_pager_update_writecount() is only valid for swap objects, skip it for unmanaged largepages.
Largepages cannot support write sealing.
Do not writecnt largepage mappings.

Reported by: kevans

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Repository

rS FreeBSD src repository - subversion

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Event Timeline

kib created this revision.Sep 10 2020, 4:48 PM

Herald added a subscriber: imp. · View Herald TranscriptSep 10 2020, 4:48 PM

kib requested review of this revision.Sep 10 2020, 4:48 PM

Harbormaster completed remote builds in B33492: Diff 76888.Sep 10 2020, 4:48 PM

markj added inline comments.Sep 10 2020, 4:52 PM

sys/kern/uipc_shm.c
1611 ↗	(On Diff #76888)	Doesn't this need to move too?

kib marked an inline comment as done.Sep 10 2020, 5:29 PM

kib added inline comments.

sys/kern/uipc_shm.c
1611 ↗	(On Diff #76888)	I think a better fix is to reset writecount to false for largepage. And not pass writecnt to shm_mmap_large at all, there is no reason to set MAP_ENTRY_WRITECNT although it is safe as nop for now.