i_gid_update(9)

💅 i_gid_update(9)

okay so bestie, welcome to the Kernel API Manual — yes, the whole manual, and today's main character is i_gid_update. it lives in section 9, which is the "kernel developer lore" section, iykyk. 🫶

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✨ NAME ✨

i_gid_update — updates @inode's i_gid field. that's it. that's the whole vibe check. 🎀

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🌸 SYNOPSIS 🌸

void i_gid_update (struct mnt_idmap *idmap , const struct iattr *attr ,
struct inode *inode );

literally three args, no return value, no drama. well. some drama, see below. 💀

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🦋 ARGUMENTS 🦋

• idmap — the idmap of the mount this inode was found from. like, which mount's identity-mapping situation are we living in rn 💫
• attr — the new attributes of the inode. the fresh fit it's about to put on ✨
• inode — the inode we're updating. the one getting the glow-up, obviously 👑

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💜 DESCRIPTION 💜

so what does it actually do? it safely updates the inode's i_gid field, and the whole point — the reason this function exists and you shouldn't just poke the field yourself, bestie, i'm begging — is that it translates the vfsgid of any idmapped mount into the filesystem's kgid. 🔥

lowkey that translation is the entire personality of this function. mount-side id vs filesystem-side id, and this is the lil fairy 🧚 that carries the value across the bridge. no cap.

don't skip the "safely" part of the description. the safety is the feature. 🙈

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👀 SEE ALSO 👀

like, the entire friend group, fr fr. all of these are kernel-file ./include/linux/fs.h besties:

• enum positive_aop_returns(9)
• struct address_space(9)
• struct file_ra_state(9)
• struct file(9)
• i_uid_into_vfsuid(9)
• i_uid_needs_update(9)
• i_uid_update(9)
• i_gid_into_vfsgid(9)
• i_gid_needs_update(9)
• inode_fsuid_set(9)
• inode_fsgid_set(9)
• fsuidgid_has_mapping(9)
• inode_set_ctime(9)
• file_write_started(9)
• file_write_not_started(9)
• struct renamedata(9)
• is_mgtime(9)
• iput_if_not_last(9)
• is_idmapped_mnt(9)
• file_start_write(9)
• file_end_write(9)
• kiocb_start_write(9)
• kiocb_end_write(9)
• name_is_dot_dotdot(9)
• name_contains_dotdot(9)
• inode_dio_begin(9)
• inode_dio_end(9)
• generic_ci_validate_strict_name(9)

like i said. the whole group chat. 💅

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and that's the page!! 🍓 this gem ships from source path ./include/linux, dated October 2026, and it goes out to every i_gid_update(9) stan. slay, stay safe, and always translate your vfsgid 💖🌈