xa_alloc(9)

✨ xa_alloc(9) — Kernel API Manual 💅

okay so bestie, this is the XArray allocation moment where the kernel goes “find me an empty little spot for this entry” and the spot selection is literally the whole plot. 🎀

🌸 NAME 🌸

xa_alloc - Find somewhere to store this entry in the XArray.

🦋 SYNOPSIS 🦋

int xa_alloc (struct xarray *xa , u32 *id , void *entry , struct
       xa_limit limit , gfp_t gfp );

🎀 ARGUMENTS 🎀

• xa — XArray. the whole data structure bestie, no cap 💖
• id — Pointer to ID. this is where the chosen index gets written ✨
• entry — New entry. the thing you're storing 🫶
• limit — Range of ID to allocate. the allowed ID zone 🌈
• gfp — Memory allocation flags. the “can I nap while doing this?” flags 😴

💖 DESCRIPTION 💖

Okay so here's the tea: xa_alloc finds an empty entry in xa between limit.min and limit.max, stores the index into the id pointer, then stores the entry at that index. A concurrent lookup will not see an uninitialised id. periodt. 💅

Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set in xa_init_flags. no cap, that's mandatory — this is not a casual suggestion, bestie 🚨

🦋 CONTEXT 🦋

Any context. Takes and releases the xa_lock. May sleep if the gfp flags permit. so yes, it can catch a nap — but only if the flags say it's allowed 😭💤

⭐ RETURN ⭐

0 on success, -ENOMEM if memory could not be allocated or -EBUSY if there are no free entries in limit. That's the whole vibe check. 💀

🌈 SEE ALSO 🌈

Kernel file ./include/linux/xarray.h plus this entire iconic little squad:

• xa_mk_value(9), xa_to_value(9), xa_is_value(9), xa_tag_pointer(9), xa_untag_pointer(9), xa_pointer_tag(9), xa_is_zero(9), xa_is_err(9), xa_err(9), struct xa_limit(9), struct xarray(9), DEFINE_XARRAY_FLAGS(9), DEFINE_XARRAY(9), DEFINE_XARRAY_ALLOC(9), DEFINE_XARRAY_ALLOC1(9), xa_init_flags(9), xa_init(9), xa_empty(9), xa_marked(9), xa_for_each_range(9), xa_for_each_start(9), xa_for_each(9), xa_for_each_marked(9),
• xa_store_bh(9), xa_store_irq(9), xa_erase_bh(9), xa_erase_irq(9), xa_cmpxchg(9), xa_cmpxchg_bh(9), xa_cmpxchg_irq(9), xa_insert(9), xa_insert_bh(9), xa_insert_irq(9), xa_alloc_bh(9), xa_alloc_irq(9), xa_alloc_cyclic(9), xa_alloc_cyclic_bh(9), xa_alloc_cyclic_irq(9), xa_reserve(9), xa_reserve_bh(9), xa_reserve_irq(9), xa_release(9),
• xa_is_sibling(9), xa_is_retry(9), xa_is_advanced(9), xa_update_node_t(9), XA_STATE(9), XA_STATE_ORDER(9),
• xas_error(9), xas_set_err(9), xas_invalid(9), xas_valid(9), xas_is_node(9), xas_reset(9), xas_retry(9), xas_reload(9), xas_set(9), xas_advance(9), xas_set_order(9), xas_set_update(9), xas_next_entry(9), xas_next_marked(9), xas_for_each(9), xas_for_each_marked(9), xas_for_each_conflict(9), xas_prev(9), xas_next(9).

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Signed off from ./include/linux, October 2026 — this is xa_alloc(9), bestie. 🫶💖