netfs_file_read_iter(9)

okay so bestie, welcome to the manual page for netfs_file_read_iter(9) from the Kernel API Manual — the Generic filesystem read routine — and the vibe is very “kernel filesystem girlie who knows her page cache” 💅✨

🎀 NAME 🎀

netfs_file_read_iter — generic filesystem read routine.

Like, that’s the whole name, no cap.

✨ SYNOPSIS ✨

ssize_t netfs_file_read_iter (struct kiocb *iocb , struct iov_iter *iter
);

🦋 ARGUMENTS 🦋

• iocb — kernel I/O control block 🧠
• iter — destination for the data read 🎯

that’s the whole cast, periodt.

💖 DESCRIPTION 💖

so like, this is the ->read_iter routine for all filesystems that can use the page cache directly. not some of them — all of the ones in that club. slay.

now the flag lore, bestie, because this is where the details live:

• The IOCB_NOWAIT flag in iocb->ki_flags says that -EAGAIN shall be returned when no data can be read without waiting for I/O requests to complete. It does not prevent readahead. no cap.
• The IOCB_NOIO flag in iocb->ki_flags says that no new I/O requests shall be made for the read or for readahead. When no data can be read, -EAGAIN shall be returned. When readahead would be triggered, a partial, possibly empty read shall be returned. it’s giving “do not start new I/O, but handle what you can” energy 🙈

👑 RETURN 👑

what comes back? glad you asked:

• number of bytes copied, even for partial reads 📦
• negative error code (or 0 if IOCB_NOIO) if nothing was read 💀

🫶 SEE ALSO 🫶

Kernel file ./fs/netfs/buffered_read.c — plus these icon functions: netfs_readahead(9), netfs_read_folio(9), netfs_write_begin(9), netfs_buffered_read_iter(9). go read them, iykyk 🌈⭐

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mwah 💋 — page source is ./fs/netfs, dated October 2026, and it belongs to netfs_file_read_iter(9). bye bestie, go read some bytes 🎀✨🫶