mapped_fsgid(9)

📦 version 7.3.1, in nixpkgs unstable

💅 mapped_fsgid — kernel API manual (section 9, bestie) 🎀

okay so welcome to the mapped_fsgid page, section 9 of the Kernel API Manual, and honestly? she's a little icon. let's get into it ✨

🌸 NAME 🌸

mapped_fsgid — returns the caller's fsgid, but mapped according to an idmapping. that's it, that's the whole vibe 🫶

✨ SYNOPSIS ✨

kgid_t mapped_fsgid (struct mnt_idmap *idmap , struct user_namespace
*fs_userns );

like yes, she takes two things and hands you back a kgid_t. no cap 💅

🦋 ARGUMENTS 🦋

  • idmap — the mount's idmapping. literally the map for the mount, bestie 🗺️
  • fs_userns — the filesystem's idmapping. yep, the fs gets its own map too 👑

🔥 DESCRIPTION 🔥

so here's the tea: use this helper to initialize a new vfs or filesystem object based on the caller's fsgid 🍓

the common example — and it's giving main character energy — is initializing the i_gid field of a newly allocated inode, triggered by a creation event such as mkdir or O_CREAT. iconic behavior honestly 👑

other examples include the allocation of quotas for a specific user. see? versatile. multi-talented. she contains multitudes 🌈

💖 RETURN 💖

the caller's current fsgid, mapped up according to idmap ⭐

🧚 SEE ALSO 🧚

kernel file ./include/linux/mnt_idmapping.h — go read her, she's the whole source of truth 📖

the whole friend group, fr fr 🫶

ngl this one is short and sweet and does exactly one thing. no drama, no undefined behavior, no deprecated warnings. we love a low-maintenance queen 💀✨

and that's the page!! brought to you by ./include/linux — the source/version line — dated October 2026 📅💜 mwah, go initialize some inodes responsibly bestie 🎀

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