make_kprojid(9)

💅 make_kprojid — Kernel API Manual, bestie edition 💅

okay so we're deep in the kernel API manual rn and today's main character is make_kprojid, from the make_kprojid(9) page. no cap, this one's short but it's giving "tiny function, big responsibility" energy 🎀

✨ NAME ✨

make_kprojid — maps a user-namespace projid pair into a kprojid. that's it, that's the whole vibe 🦋

✨ SYNOPSIS ✨

kprojid_t make_kprojid (struct user_namespace *ns , projid_t projid );

literally copy that exactly, don't be cute with the spacing, the kernel does not find it funny 😭

✨ ARGUMENTS ✨

• ns — the user namespace that the projid is chillin' in 🏠
• projid — the project identifier itself, the little guy we're mapping 💖

✨ DESCRIPTION ✨

so what it does: it maps a user-namespace uid pair into a kernel internal kuid, and returns that kuid. yes, that is genuinely what the page says, word for word — we are not editorialising, we are simply reporting the tea ☕✨

and here's the part you actually need to remember, bestie 👑: when there is no mapping defined for the user-namespace projid pair, INVALID_PROJID is returned.

⚠️ callers are expected to test for and handle INVALID_PROJID being returned. like, this is not optional, this is not a "later" task, this is a "do it or your code is a mess" task 💀

also very slay of the kernel: INVALID_PROJID may be tested for using projid_valid. use the helper, it's there for you, it loves you 🫶

✨ SEE ALSO ✨

• kernel file ./kernel/user_namespace.c — the source, the origin story, the lore 🌈
• make_kuid(9)
• from_kuid(9)
• from_kuid_munged(9)
• make_kgid(9)
• from_kgid(9)
• from_kgid_munged(9)
• from_kprojid(9)
• from_kprojid_munged(9)
• verify_root_map(9)

and that's the page!! from the ./kernel source, dated October 2026, under the name make_kprojid(9) — go forth, validate your projids, and slay 💅🌸🦋