lookup_one_p...ive_unlocked(9)

💅 lookup_one_p...ive_unlocked — a Kernel API Manual moment

okay bestie, welcome to the Kernel API Manual, where today's main character is lookup_one_p...ive_unlocked(9) 🎀 (yes the header truncates it, we don't gatekeep, the full name is lookup_one_positive_unlocked). this one's a little lookup helper and it's honestly kind of iconic for knowing what it wants. let's get into it ✨

🌸 NAME 🌸

lookup_one_positive_unlocked — lookup single pathname component. one component. just one. it's giving "i do one thing and i do it well" 💅

🦋 SYNOPSIS 🦋

struct dentry * lookup_one_positive_unlocked (struct mnt_idmap *idmap ,
struct qstr *name , struct dentry *base );

✨ ARGUMENTS ✨

• idmap — the idmap of the mount that the lookup is performed from 🫶
• name — the qstr holding the pathname component you want looked up
• base — the base directory to lookup from, your starting point, your home base 💖

💜 DESCRIPTION 💜

okay so here's the vibe: this helper will yield ERR_PTR(-ENOENT) on negatives. like, if it's a no, it's a whole error pointer no, not a weird maybe. and the helper returns either a known positive or ERR_PTR. no gray area, no "it's complicated" situationship. that's literally what most of the users want 😌

⚠️ now for the careful part, bestie — a pinned negative with an unlocked parent can become positive at any time, so callers of lookup_one_unlocked need to be very careful. meanwhile pinned positives have >d_inode stable, so this one avoids such problems. it's giving stable queen energy 👑

this can be used for in-kernel filesystem clients such as file servers. lowkey its whole purpose 🍓

and the helper should be called without i_rwsem held. no cap. don't hold it. 🙈

🔥 RETURN 🔥

a positive dentry, or:

• ERR_PTR(-ENOENT) if the name could not be found, or
• the same errors as lookup_one_unlocked.

periodt. that's the return contract 💀

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🌈 SEE ALSO 🌈

the kernel file ./fs/namei.c and honestly the entire friend group — here's everybody, no one left out of the group chat 💖

• check_acl(9), acl_permission_check(9), generic_permission(9), do_inode_permission(9), sb_permission(9), inode_permission(9), path_get(9), path_put(9)
• path_connected(9), try_to_unlazy(9), try_to_unlazy_next(9), complete_walk(9), may_follow_link(9), safe_hardlink_source(9), may_linkat(9), may_create_in_sticky(9)
• lookup_fast(9), start_dirop(9), end_dirop(9), kern_path_parent(9), vfs_path_parent_lookup(9), vfs_path_lookup(9), try_lookup_noperm(9), lookup_noperm(9)
• lookup_one(9), lookup_one_unlocked(9), lookup_one_positive_killable(9), lookup_noperm_unlocked(9), start_creating(9), start_removing(9), start_creating_killable(9), start_removing_killable(9)
• start_creating_noperm(9), start_removing_noperm(9), start_creating_dentry(9), start_removing_dentry(9), __start_renaming(9), start_renaming(9)
• start_renaming_dentry(9), start_renaming_two_dentries(9), vfs_prepare_mode(9), vfs_create(9), atomic_open(9), vfs_lookup_open(9), vfs_tmpfile(9)
• kernel_tmpfile_open(9), end_creating_path(9), dentry_create(9), vfs_mknod(9), vfs_mkdir(9), vfs_rmdir(9), vfs_unlink(9), vfs_symlink(9)
• vfs_link(9), vfs_rename(9), vfs_readlink(9), vfs_get_link(9), page_get_link(9), page_put_link(9)

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okay that's the whole page, mwah 💋 this was brought to you by the source ./fs, version date October 2026, and the page lookup_one_p...ive_unlocked(9) — stay positive (dentry-wise), stay unlocked (parent-wise), and don't hold i_rwsem 💅🧚💜