cgroup_writeback_umount(9)

Hey bestie 💖 welcome to cgroup_writeback_umount(9) from the Kernel API Manual — this one is lowkey a “wait for the workers to finish” situation, and it’s giving very patient-main-character energy 🎀

✨ NAME ✨

cgroup_writeback_umount — wait for in-flight inode wb switches on @sb 🦋

🌸 SYNOPSIS 🌸

void cgroup_writeback_umount (struct super_block *sb );

💅 ARGUMENTS 💅

• sb — target super_block 👑

🔥 DESCRIPTION 🔥

Okay so this function waits until every inode wb switch that already passed the SB_ACTIVE check on this superblock has been completed by the worker. No cap, that’s the whole vibe: let the already-started switches finish 🫶

Since SB_ACTIVE is cleared before this is called, no new switches can start for sb, so s_isw_nr_in_flight will monotonically drop to zero. It’s literally a one-way trip down to zero, and we love that for it 📉

🌈 SEE ALSO 🌈

Kernel file ./fs/fs-writeback.c — go check out these iconic neighbors 👀✨

• inode_io_list_move_locked(9)
• wb_wait_for_completion(9)
• inode_cgwb_move_to_attached(9)
• locked_inode_to_wb_and_lock_list(9)
• inode_to_wb_and_lock_list(9)
• inode_switch_wbs(9)
• cleanup_offline_cgwb(9)
• wbc_attach_and_unlock_inode(9)
• wbc_attach_fdatawrite_inode(9)
• wbc_detach_inode(9)
• wbc_account_cgroup_owner(9)
• wb_split_bdi_pages(9)
• bdi_split_work_to_wbs(9)
• cgroup_writeback_by_id(9)
• wb_start_background_writeback(9)
• filemap_dontcache_kick_writeback(9)
• __mark_inode_dirty(9)
• writeback_inodes_sb_nr(9)
• writeback_inodes_sb(9)
• try_to_writeback_inodes_sb(9)
• sync_inodes_sb(9)
• write_inode_now(9)
• sync_inode_metadata(9)

mwah 💋 — source/version ./fs, date October 2026.