filemap_splice_read(9)

📦 version 7.3.1, in nixpkgs unstable

💅 filemap_splice_read(9) — fresh from the Kernel API Manual ✨

okay bestie, gather round 🫶 this one is all about yeeting a file's pagecache data into a pipe, and honestly? iconic behavior. no cap.

🎀 NAME 🎀

filemap_splice_read — splice data from a file's pagecache into a pipe 💖

✨ SYNOPSIS ✨

ssize_t filemap_splice_read (struct file *in , loff_t *ppos , struct
pipe_inode_info *pipe , size_t len , unsigned int flags );

💖 ARGUMENTS 💖

  • in — the file you're reading from, bestie 🌸
  • ppos — pointer to the file position you're reading from, lowkey important 📍
  • pipe — the pipe getting spliced into 🎀
  • len — how much you wanna splice, literally the amount ✨
  • flags — the SPLICE_F_* flags, iykyk 🦋

🌸 DESCRIPTION 🌸

so this function grabs folios from a file's pagecache and splices them into the pipe 💅 readahead gets called as necessary to fill more folios, which is giving “we got more where that came from” energy. oh, and it may be used for blockdevs also — periodt. 🔥

🦋 RETURN 🦋

on success, the number of bytes read gets returned and *ppos will be updated if appropriate 🫶 0 gets returned if there's no more data to be read; -EAGAIN gets returned if the pipe had no space; and some other negative error code gets returned on error 😭 also a short read may occur if the pipe has insufficient space, we reach the end of the data, or we hit a hole — yeah, that's the vibe check 💀

👑 SEE ALSO 👑

the whole squad is here, bestie — Kernel file ./mm/filemap.c plus:

that's the whole page, babe 💌 brought to you by source/version ./mm, dated October 2026 — mwah, slay, and happy splicing 🫶✨

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