do_lookup_nm(9)

💅 do_lookup_nm(9) — the kernel API manual, but make it make sense

okay so this is a page from the Kernel API Manual (yes, section 9, the kernel-y one) and honestly? it's a whole vibe. we're talking about do_lookup_nm today bestie, so grab a strawberry drink 🍓 and let's get into it.

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✨ NAME ✨

do_lookup_nm — look up a "hashed" node. that's it, that's the tweet. 👑

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🌸 SYNOPSIS 🌸

int do_lookup_nm (struct ubifs_info *c , const union ubifs_key *key ,
void *node , const struct fscrypt_name *nm );

like, four things go in, an int comes out. main character signature fr fr.

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🎀 ARGUMENTS 🎀

• c — the UBIFS file-system description object. the whole file system's little ID card, basically 🪪
• key — the node key we're looking up. this is the search term, the vibe check, the ~what are we even here for~ 🔍
• node — the node gets returned here. it's an out-param bestie, you bring the bucket, the function fills it 🪣
• nm — the node name. the name-name, not the hashed-ish name 💌

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🦋 DESCRIPTION 🦋

so the way that this function works is — it looks up and reads a node that contains the name hash in the key. periodt. 💅

but here's the thing: because the hash can have collisions 😭 there may be many nodes sharing the exact same key. so no, we can't just grab the first one and call it a day (not me being lazy). we have to sequentially look at all of them until the needed one is found. one by one. icon behavior, honestly 🧚

as for what it returns:

• 0 if it's a success — slay ✨
• -ENOENT if the node was not found — it's giving ghosted 💀
• a negative error code if something failed — rough, but we move 🙈

ngl, that collision part is the whole plot. don't skip it. the hash matching key does not guarantee you found the right node, so the scan is not optional. 🔥

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🌈 SEE ALSO 🌈

all the siblings, cousins, and adjacent characters in the family group chat — every single one of them, no cap:

kernel file ./fs/ubifs/tnc.c and then, breathe, here we go:

insert_old_idx(9), insert_old_idx_znode(9), ins_clr_old_idx_znode(9), destroy_old_idx(9), copy_znode(9), add_idx_dirt(9), replace_znode(9), dirty_cow_znode(9), lnc_add(9), lnc_free(9), tnc_read_hashed_node(9), try_read_node(9), fallible_read_node(9), matches_name(9), get_znode(9), tnc_next(9), tnc_prev(9), resolve_collision(9), fallible_matches_name(9), fallible_resolve_collision(9), matches_position(9), resolve_collision_directly(9), dirty_cow_bottom_up(9), ubifs_lookup_level0(9), lookup_level0_dirty(9), maybe_leb_gced(9), ubifs_tnc_locate(9), ubifs_tnc_get_bu_keys(9), read_wbuf(9), validate_data_node(9), ubifs_tnc_bulk_read(9), ubifs_tnc_lookup_nm(9), ubifs_tnc_lookup_dh(9), correct_parent_keys(9), insert_zbranch(9), tnc_insert(9), ubifs_tnc_add(9), ubifs_tnc_replace(9), ubifs_tnc_add_nm(9), tnc_delete(9), ubifs_tnc_remove(9), ubifs_tnc_remove_nm(9), ubifs_tnc_remove_dh(9), key_in_range(9), ubifs_tnc_remove_range(9), ubifs_tnc_remove_ino(9), ubifs_tnc_next_ent(9), tnc_destroy_cnext(9), ubifs_tnc_close(9), left_znode(9), right_znode(9), lookup_znode(9), is_idx_node_in_tnc(9), is_leaf_node_in_tnc(9), ubifs_tnc_has_node(9), ubifs_dirty_idx_node(9), dbg_check_inode_size(9).

like, that's the entire friend group. say hi to all of them or it's weird. 🫶

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and that's the page! 🎀 it comes to you courtesy of the source ./fs/ubifs, dated October 2026 — so mark your calendar bestie, this manual page is a Scorpio (or maybe a Libra, don't quote me) and it said see you then. mwah 💖