3/3 vfs: refactor vputx and add more comments
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Authored by mjg on Feb 6 2020, 12:20 AM.

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kib
jeff

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rS357812: vfs: refactor vputx and add more comment

Summary

the vnode interlock relocking for vchr in vrele may seem problematic, but it almost never happens in practice. I take it for readability.

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rS FreeBSD src repository - subversion

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Buildable 29199

mjg retitled this revision from vfs: refactor vputx and add more comments to 3/3 vfs: refactor vputx and add more comments.Feb 6 2020, 12:20 AM

mjg edited the summary of this revision. (Show Details)

tested by pho

sys/kern/vfs_subr.c
3200	Can we rename this vput_final or vput_last or something. At first glance it was confusing to me for historical reasons.
3327	It's not clear to me why all of the release routines don't have this VCHR code.

sys/kern/vfs_subr.c
2802–2804	The caller is required to hold the interlock when transitioning a VCHR usecount to zero. This prevents a race with devfs_reclaim_vchr() that would leak a si_usecount reference. The vnode lock will also prevent this race if it is held while dropping the last ref.
2810	vrele() decr v_usecount
2812	v_usecount == 0, does not decrement si_usecount v_rdev = NULL
2817	v_decr_devcount() v_dev == NULL, does not decrement si_usecount