must_set_pos(9)

💖 must_set_pos(9) — check whether f_pos has to be updated 💖

okay so welcome to the Kernel API Manual, bestie. This is the must_set_pos(9) page, and it's giving “very specific seek-check energy.” No cap, the whole point is checking whether f_pos has to be updated — and if you're here, you probably need the tea. ✨

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🌸 NAME 🌸

must_set_pos — check whether f_pos has to be updated. That's the name, that's the vibe, that's the whole assignment. 🎀

✨ SYNOPSIS ✨

here's the exact signature, copied with love and zero typos:

int must_set_pos (struct file *file , loff_t *offset , int whence ,
       loff_t eof );

It returns an int and takes struct file *file, loff_t *offset, int whence, and loff_t eof. The whole cast showed up. 🌈

💅 ARGUMENTS 💅

Four args, four little besties — let's meet them:

• file — file to seek on
• offset — offset to use
• whence — type of seek operation
• eof — end of file

🦋 DESCRIPTION 🦋

Check whether f_pos needs to be updated and update offset according to whence.

That's literally the whole description, bestie. It's a vibe check on f_pos, plus the offset update according to whence. 😭💅

🎀 RETURN 🎀

The return-value tea:

• 0 if f_pos doesn't need to be updated
• 1 if f_pos has to be updated
• negative error code on failure

So yeah: 0 = no update needed, 1 = update time, negative = something went wrong. Slay. ✨

🔥 SEE ALSO 🔥

Kernel file ./fs/read_write.c is the homebase, and these are the icons to go peek at:

• vfs_setpos_cookie(9)
• vfs_setpos(9)
• generic_file_llseek_size(9)
• generic_llseek_cookie(9)
• generic_file_llseek(9)
• fixed_size_llseek(9)
• no_seek_end_llseek(9)
• no_seek_end_llseek_size(9)
• noop_llseek(9)

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xoxo, source/version: ./fs, date: October 2026 — must_set_pos(9) out 💅