VOP_CLOSE(): MNTK_EXTENDED_SHARED filesystems do not need excl lock
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Authored by kib on Apr 24 2023, 10:50 PM.

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Reviewers

jhb
markj

Commits

rG37e6036b26cd: VOP_CLOSE(): MNTK_EXTENDED_SHARED filesystems do not need excl lock

Summary

All in-tree implementations of VOP_CLOSE() for filesystems proclaiming
MNTK_EXTENDED_SHARED, are fine with the shared lock for the closed
vnode.  I checked the following implementations:
        ffs
        ext2
        ufs
        null
        tmpfs
        devfs
        fdescfs
        cd9660
        zfs
It seems that initial addition of FWRITE check was due to necessity of
handling the VV_TEXT vnode vflag.  Since VOP_ADD_WRITECOUNT() only
requires shared lock, we can relax the locking requirement there.

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rG FreeBSD src repository

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Event Timeline

kib created this revision.Apr 24 2023, 10:50 PM

Herald added a subscriber: imp. · View Herald TranscriptApr 24 2023, 10:50 PM

kib requested review of this revision.Apr 24 2023, 10:50 PM

kib added reviewers: jhb, markj.

kib added a subscriber: olce.

markj accepted this revision.Apr 25 2023, 1:16 PM

This revision is now accepted and ready to land.Apr 25 2023, 1:16 PM

FWIW, I've checked these filesystems as well and I concur. I've also tested the patch with a parallel buildkernel and several find processes repeatedly cating files in /usr/obj without problems.