STRUCT LOOP_CONFIG(9)

💅 struct loop_config(9) — like, the whole vibe of a loop device config, in one struct

okay so bestie, we're in the Kernel API Manual today and the main character is struct loop_config. yes it's a struct, yes it's lowkey iconic, and yes it's gonna make your loop device setup so much cleaner. let's get into it 🫶

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✨ NAME ✨

struct loop_config — the complete configuration for a loop device. like, everything it needs to know about itself, all in one place. no cap. 💖

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🌸 SYNOPSIS 🌸

struct loop_config {
    __u32 fd;
    __u32 block_size;
    struct loop_info64      info;
    __u64 __reserved[8];
 };

look at her. so neat. so organized. we stan a well-structured struct ✨

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🎀 Members 🎀

• fd — the fd of the file that's gonna be the backing file for the loop device. that's the whole point of the thing, fr fr.
• block_size — the block size to use. that said… she's ignored if it's 0, so don't come crying to me if you set it to zero and nothing happens 🙈
• info — the struct loop_info64 you're configuring the loop device with. yes, all of it. she contains multitudes 💅

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🦋 Description 🦋

so this structure is the one you use with the LOOP_CONFIGURE ioctl, and here's the slay: you can use it to atomically set up and configure all the loop device parameters at once. all at once!! no doing it one by one like some kind of peasant. atomic setup is the moment, it's giving efficiency, it's giving main character energy 👑

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🌈 SEE ALSO 🌈

• Kernel file ./include/uapi/linux/loop.h — go read her, she's the source of truth 💜

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lowkey reminder bestie: __reserved[8] is there for a reason, so don't go poking at it, ok? she's reserved. respect her space 🧚

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and that's the page!! mwah 💋 this lil writeup lives in ./include/uapi/linux and it's dated October 2026 — so yeah, mark your calendars, screenshot it, send it to the group chat, struct loop_config(9) ate and left no crumbs 🍓⭐