Differential D59982

lockf: Do not block in vfs_busy()
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Authored by markj on Thu, Sep 24, 1:51 PM.

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	F173261312: D59982.id187598.diff
	Thu, Sep 24, 7:14 PM

	F173254215: D59982.diff
	Thu, Sep 24, 5:57 PM

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rGdd16a5f53b0b: lockf: Do not block in vfs_busy()

Summary

I believe a race is possible otherwise: vfs_busy() may return after an
unmounted filesystem has been removed from the global mount list.
That is, vfs_busy() will block until vfs_mount_destroy() sets
MNTK_REFEXPIRE, and at that point the mountpoint has been removed from
the mountlist, so TAILQ_FOREACH can return an invalid value.

Simply do not block if the mountpoint is being unmounted.

Fixes: eca39864f702 ("Add sysctl KERN_LOCKF")

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rG FreeBSD src repository

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Event Timeline

markj created this revision.Thu, Sep 24, 1:51 PM

Herald added subscribers: olce, imp. · View Herald TranscriptThu, Sep 24, 1:51 PM

markj requested review of this revision.Thu, Sep 24, 1:51 PM

Harbormaster completed remote builds in B77272: Diff 187598.Thu, Sep 24, 1:51 PM

kib accepted this revision.Thu, Sep 24, 4:13 PM

This revision is now accepted and ready to land.Thu, Sep 24, 4:13 PM

Closed by commit rGdd16a5f53b0b: lockf: Do not block in vfs_busy() (authored by markj). · Explain WhyThu, Sep 24, 4:20 PM

This revision was automatically updated to reflect the committed changes.

markj added a commit: rGdd16a5f53b0b: lockf: Do not block in vfs_busy().

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sys/

kern/

2 lines

Diff 187616

sys/kern/kern_lockf.c

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