misc_cg_max_write(9)

💅 misc_cg_max_write(9) — the cgroup glow-up manual (Kernel API Manual)

okay so bestie, you found misc_cg_max_write(9), and honestly? it's giving "small function, big responsibility" ✨ this is the kernel API manual version, and we're gonna walk through it together, no cap 🫶

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🌸 NAME 🌸

misc_cg_max_write — updates the maximum limit of the cgroup. that's it, that's the whole job. iconic, honestly 👑

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✨ SYNOPSIS ✨

ssize_t misc_cg_max_write (struct kernfs_open_file *of , char *buf ,
       size_t nbytes , loff_t off );

look at that signature. four args, one ssize_t coming back at you. slay 💅

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🎀 ARGUMENTS 🎀

• of — handler for the file. your little passport to the kernfs file, basically 🦋
• buf — the data from the user. and listen, it has to be either "max", or 0, or a positive integer. no vibes-based input allowed, the vibe check is strict 🙈
• nbytes — number of bytes of the data. yes, somebody's counting 📏
• off — offset in the file. where you are in the file, lowkey 🗺️

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💖 DESCRIPTION 💖

so the user can pass data like:

echo sev 23 > misc.max

OR

echo sev max > misc.max

both are valid, both are welcome, we love options 🍓

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🧚 CONTEXT 🧚

Any context. literally any. no restrictions, no dress code, come as you are 🌈

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🔥 RETURN 🔥

• >= 0 — number of bytes processed in the input. good vibes, successful run ✅
• -EINVAL — if buf is not valid. you gave it something it can't work with, and it's telling you 💀
• -ERANGE — if number is bigger than the u64 capacity. too much!! overflowing!! the number ate too much and now it's out of range 😭

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👑 SEE ALSO 👑

Kernel file ./kernel/cgroup/misc.c, plus the whole friend group:

parent_misc(9), valid_type(9), misc_cg_set_capacity(9), misc_cg_cancel_charge(9), misc_cg_try_charge(9), misc_cg_uncharge(9), misc_cg_max_show(9), misc_cg_current_show(9), misc_cg_peak_show(9), misc_cg_capacity_show(9), misc_cg_alloc(9), misc_cg_free(9)

like, the whole squad showed up for this one 🫶✨

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and that's the page, bestie 💜 it lives in ./kernel/cgroup, dated October 2026, and it's misc_cg_max_write(9) forever and always. periodt 🌸🎀