mapped_fsuid(9)

okay so, bestie, welcome to mapped_fsuid(9) — the Kernel API Manual page that's about to make idmapping make sense, fr fr. 💖

🌸 NAME 🌸

mapped_fsuid — return caller's fsuid mapped according to an idmapping.

✨ SYNOPSIS ✨

kuid_t mapped_fsuid (struct mnt_idmap *idmap , struct user_namespace
       *fs_userns );

🎀 ARGUMENTS 🎀

• idmap — the mount's idmapping. yes, the mount's 💅
• fs_userns — the filesystem's idmapping. the filesystem's, periodt 🦋

🦋 DESCRIPTION 🦋

Use this helper to initialize a new vfs or filesystem object based on the caller's fsuid. it's giving "set up the new thing with the right identity" ✨

A common example is initializing the i_uid field of a newly allocated inode triggered by a creation event such as mkdir or O_CREAT. like when a new inode is born and needs its i_uid set 🎀

Other examples include the allocation of quotas for a specific user. quota allocation for one specific user, iykyk 💜

👑 RETURN 👑

The caller's current fsuid mapped up according to idmap. that's the return value, bestie 👑

🌈 SEE ALSO 🌈

Kernel file ./include/linux/mnt_idmapping.h — and the whole squad is:

• vfsuid_eq_kuid(9)
• vfsgid_eq_kgid(9)
• vfsuid_has_fsmapping(9)
• vfsuid_into_kuid(9)
• vfsgid_has_fsmapping(9)
• vfsgid_into_kgid(9)
• mapped_fsgid(9)

kisses and kernel hugs 🫶 — this mapped_fsuid(9) page comes from ./include/linux, and it's dated October 2026, periodt. 💅