mapping_seek_hole_data(9)

📦 version 7.3.1, in nixpkgs unstable

🎀 NAME 🎀

okay so this is the Kernel API Manual entry for mapping_seek_hole_data(9), and it is lowkey iconic. 💅

  • mapping_seek_hole_data — seek for SEEK_DATA / SEEK_HOLE in the page cache. bestie, that's the whole vibe. ✨

🌸 SYNOPSIS 🌸

the signature is giving main character energy, fr fr:

loff_t mapping_seek_hole_data (struct address_space *mapping , loff_t
start , loff_t end , int whence );

🦋 ARGUMENTS 🦋

  • mapping — the address space to search. that's the zone you're snooping around in. 🔍
  • start — first byte to consider. the starting line, no cap.
  • end — limit of search, and yes it's exclusive. do not forget, bestie. 🙈
  • whence — either SEEK_HOLE or SEEK_DATA. pick your fighter. ⚔️

💖 DESCRIPTION 💖

so if the page cache knows which blocks contain holes and which blocks contain data, your filesystem can use this function to implement SEEK_HOLE and SEEK_DATA. that's the whole point, and it ate. 🔥

this is useful for filesystems that are entirely memory-based — such as tmpfs — and for filesystems that support unwritten extents. yep, both of those girlies get to use it. 🫶

⭐ RETURN ⭐

on success you get the requested offset back. slay. ✨

but if whence specifies SEEK_DATA and there is no data after start, you get -ENXIO. that's the "no data here, bestie" signal. 💀

also, there is an implicit hole after end - 1, so SEEK_HOLE returns end if all the bytes between start and end contain data. literally important, don't skip it. 👑

🌈 SEE ALSO 🌈

Kernel file ./mm/filemap.c is the homebase, and the whole SEE ALSO crew is right here — go say hi:

that's the page, bestie — source/version ./mm, dated October 2026, and yes she ate. mwah 💋🎀

📦 where this page comes from