write_head(9)

✨ write_head(9) — Kernel API Manual ✨

okay bestie, we're in the Kernel API Manual and this page is literally all about write_head. Buckle up, it's giving "tiny function, very specific UBIFS job." 💅

🌸 NAME 🌸

write_head — write data to a journal head. That's it, that's the whole name section, and it ate. 🫶

🦋 SYNOPSIS 🦋

the signature is right here, copy it exactly, no improv:

int write_head (struct ubifs_info *c , int jhead , void *buf , int len ,
       int *lnum , int *offs , int sync );

🎀 ARGUMENTS 🎀

• c — UBIFS file-system description object. the context bestie, the main-character struct. 💖
• jhead — journal head. the head we're writing into. 👑
• buf — buffer to write. the actual data vibe. 🍓
• len — length to write. how much of the buffer is coming with us. ✨
• lnum — LEB number written is returned here. yes, this is where that output goes. 🔥
• offs — offset written is returned here. the offset output lives here too. 🌈
• sync — non-zero if the write-buffer has to by synchronized. (that wording is literally from the page, bestie 😭) 💀

💜 DESCRIPTION 💜

okay so write_head writes data to the reserved space of journal head jhead. It returns zero in case of success — slay — and a negative error code in case of failure — not slay, but important. 💅

no cap, that's the behavior: zero on success, negative error code on failure. periodt. 🎀

🧚 SEE ALSO 🧚

the Kernel file ./fs/ubifs/journal.c is in the group chat, along with this whole friend list:

• zero_ino_node_unused(9)
• zero_dent_node_unused(9)
• zero_trun_node_unused(9)
• reserve_space(9)
• __queue_and_wait(9)
• wait_for_reservation(9)
• wake_up_reservation(9)
• add_or_start_queue(9)
• make_reservation(9)
• release_head(9)
• finish_reservation(9)
• get_dent_type(9)
• pack_inode(9)
• mark_inode_clean(9)
• ubifs_jnl_update(9)
• ubifs_jnl_write_data(9)
• ubifs_jnl_write_inode(9)
• ubifs_jnl_delete_inode(9)
• ubifs_jnl_xrename(9)
• ubifs_jnl_rename(9)
• truncate_data_node(9)
• ubifs_jnl_truncate(9)
• ubifs_jnl_delete_xattr(9)
• ubifs_jnl_change_xattr(9)

💌 cute sign-off: source/version is ./fs/ubifs, the date is October 2026, and the page is write_head(9). mwah, bestie, go write some journal-head data responsibly 🫶💖