btree_get_prev(9)

🦋 btree_get_prev — the "wait, go back one" function, bestie

Ok so real talk, this page is from the Kernel API Manual, section 9, and it's about btree_get_prev. Yes it's a kernel thing. Yes you're gonna get it. Let's go 💅

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✨ SYNOPSIS ✨

void * btree_get_prev (struct btree_head *head , struct btree_geo *geo ,
unsigned long *key );

That's the whole signature, no cap. Returns a void *, takes three things. Slay.

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🎀 ARGUMENTS 🎀

• head — the btree head. Like, the actual btree you're digging around in. 🌸
• geo — the btree geometry. It's the shape/layout info, lowkey important.
• key — a pointer to the key. Yeah, a pointer, not the key itself. Pay attention bestie 👀

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💖 DESCRIPTION 💖

So here's the vibe: this function returns the next item right before the value pointed to by key. And it doesn't just hand you the item — it updates key with its key too. Two-for-one, iconic. 🫶

And if there's no entry whose key is smaller than the one you gave it? You get NULL back. That's it, that's the whole story. No entry smaller = no entry, periodt. 💀

Ngl, remember it's "previous" in key order, and it's doing a little mutation on your key on the way out. That's not me adding lore, that's literally what the man page says.

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🌈 SEE ALSO 🌈

Kernel file ./include/linux/btree.h — and honestly the whole btree friend group, go say hi:

• B+Tree basics(9)
• struct btree_head(9)
• btree_alloc(9)
• btree_free(9)
• btree_init_mempool(9)
• btree_init(9)
• btree_destroy(9)
• btree_lookup(9)
• btree_insert(9)
• btree_update(9)
• btree_remove(9)
• btree_merge(9)
• btree_last(9)

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K bye bestie, this page lives in ./include/linux and it's dated October 2026 — go get that previous entry, you've got this 💜✨