netfs_buffer..._iter_locked(9)

netfs_buffer..._iter_locked(9) 💅

🌸 NAME 🌸

netfs_buffered_write_iter_locked — write data to a file. Bestie, this is from the Kernel API Manual and it's giving “the actual write-work function” energy ✨

✨ SYNOPSIS ✨

ssize_t netfs_buffered_write_iter_locked (struct kiocb *iocb , struct iov_iter *from , struct netfs_group *netfs_group );

💖 ARGUMENTS 💖

• iocb — IO state structure (file, offset, etc.) 🫶
• from — iov_iter with data to write
• netfs_group — grouping for dirty folios (eg. ceph snaps).

🎀 DESCRIPTION 🎀

Okay so this function literally does all the work needed for actually writing data to a file. It does all the basic checks, removes SUID from the file, updates modification times, and calls the proper subroutines depending on whether we do direct IO or a standard buffered write. Slay 💅

The caller must hold appropriate locks around this function and have called generic_write_checks already. The caller is also responsible for doing any necessary syncing afterwards. Important bestie note 🫶

This function does not take care of syncing data in case of O_SYNC write. A caller has to handle it. This is mainly due to the fact that we want to avoid syncing under i_rwsem. Periodt 💀

🫶 RETURN 🫶

• number of bytes written, even for truncated writes
• negative error code if no data has been written at all

👀 SEE ALSO 👀

Kernel file ./fs/netfs/buffered_write.c netfs_perform_write(9), netfs_file_write_iter(9).

later bestie — source/version: ./fs/netfs, date: October 2026 🦋💖