xa_extract(9)

💖 xa_extract(9) — the group-chat guide 💖

okay bestie, welcome to the Kernel API Manual, section 9, and today's main character is xa_extract. no cap, this one's genuinely a vibe. ✨

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🌸 NAME 🌸

xa_extract — literally copies the entries you picked out of the XArray and drops them into a normal array. that's it, that's the whole gig. 🎀

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🦋 SYNOPSIS 🦋

unsigned int xa_extract (struct xarray *xa , void **dst , unsigned long
start , unsigned long max , unsigned int n , xa_mark_t filter );

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⭐ ARGUMENTS ⭐

• xa — the source XArray you're copying from. your origin story, if you will. 💜
• dst — the buffer everything gets copied into. the destination, the glow-up location. 🫶
• start — the first index in the XArray that's even eligible to be selected. lower bound, bestie. 🍓
• max — the last index in the XArray eligible to be selected. upper bound, the cutoff. 🌸
• n — the maximum number of entries to copy. like a guest list with a capacity, respectfully. 🎀
• filter — the selection criterion. who gets in, who doesn't. the bouncer, basically. 💅

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✨ DESCRIPTION ✨

so here's the teaaa: it copies up to n entries that match filter from the XArray, and the copied entries will have indices between start and max, inclusive. inclusive is the key word there, don't forget it. 🌈

the filter can be an XArray mark value — in which case, entries that are marked with that mark get copied. it can also be XA_PRESENT, in which case all the entries that are not NULL get copied. simple as that. 💖

🫶 important vibe check: the entries returned may not represent a snapshot of the XArray at a moment in time. lowkey the most important sentence on this whole page, ngl.

like, for example: if another thread stores to index 5, then index 10, calling xa_extract may return the old contents of index 5 and the new contents of index 10. it's giving "mixed eras" 😭. the good news though — indices not modified while this function is running will not be skipped. so nothing gets ghosted. 💀

if you need stronger guarantees, holding the xa_lock across calls to this function will prevent concurrent modification. that's the secure-the-bag move. 👑

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🔥 CONTEXT 🔥

any context, queen. it takes and releases the RCU lock. that's it. 🌟

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👑 RETURN 👑

the number of entries copied. that's the whole return value, no plot twist. 🎀

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💫 SEE ALSO 💫

kernel file ./lib/xarray.c, plus the whole extended friend group:

xas_load(9), xas_nomem(9), xas_free_nodes(9), xas_create_range(9), xas_store(9), xas_get_mark(9), xas_set_mark(9), xas_clear_mark(9), xas_init_marks(9), xas_split_alloc(9), xas_split(9), xas_try_split_min_order(9), xas_try_split(9), xas_pause(9), xas_find(9), xas_find_marked(9), xas_find_conflict(9), xa_load(9), __xa_erase(9), xa_erase(9), __xa_store(9), xa_store(9), __xa_cmpxchg(9), __xa_insert(9), xa_store_range(9), xas_get_order(9), xa_get_order(9), __xa_alloc(9), __xa_alloc_cyclic(9), __xa_set_mark(9), __xa_clear_mark(9), xa_get_mark(9), xa_set_mark(9), xa_clear_mark(9), xa_find(9), xa_find_after(9), xa_delete_node(9), xa_destroy(9)

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k byeee, this page came from ./lib, dated October 2026 — mwah, slay, periodt 💅✨