VREF(9)

💅 VREF(9) — like, the vnode reference counter manual, bestie

okay so this is a page from the Kernel Developer's Manual (that's the manual name, iykyk 🎀) and honestly it's short but it matters, so let's get into it ✨

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✨ NAME ✨

vref, vrefl — increment the use count for a vnode

like literally that's the whole job. bumping the counter. no cap. 💅

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🌸 SYNOPSIS 🌸

#include <sys/param.h>
#include <sys/vnode.h>

void
vref(struct vnode *vp);

void
vrefl(struct vnode *vp);

two functions, both void, both take a struct vnode *vp, both return nothing because they're too busy slaying 🦋

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💖 DESCRIPTION 💖

So bestie, the tea is: these functions increment the v_usecount field of a vnode. That's it. That's the whole vibe check. ✨

• vp — the vnode to increment 🫶

okay but why do we care, right? because every single vnode keeps a reference count of how many parts of the system are using it. think of it as a little tally of everyone who's currently obsessed with that vnode 💀 and the whole point is that this lets the system detect when a vnode is no longer being used — and once nobody's using it, it can be safely recycled for a different file. so it's giving responsible resource management, main character energy for the kernel 🔥

the rule, fr fr: any code in the system which is using a vnode (like, during the operation of some algorithm, or to store in a data structure) should call vref() or vrefl(). no excuses, no skipping, periodt 👑

and here's the difference between the two, pay attention because this is the part people mess up 🙈

• vref() locks the vnode interlock while it does its thing
• vrefl() expects the interlock to already be held — so like, it's on you, you better already have it 😭

so if you call vrefl() without already holding the interlock, that's a you problem, not a vrefl() problem. pick the right one, bestie 💅

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🦋 SEE ALSO 🦋

• vget(9)
• vnode(9)
• vput(9)
• vrefcnt(9)
• vrele(9)

the whole vnode friend group, go read them too, they all ate 🌈

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👑 AUTHORS 👑

This manual page was written by Doug Rabson. iconic behaviour honestly, thank you Doug 🫶

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and that's the page!! this version came to you from Debian, dated January 18, 2016, filed under VREF(9) — mwah, go increment some counters responsibly bestie 💜✨