folio_wait_writeback(9)

💾 folio_wait_writeback(9) — bestie edition

Okay so this is from the Kernel API Manual, and the function is folio_wait_writeback(9). Strap in, it's a short one but it's lowkey doing Important Work. 🫶

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✨ NAME ✨

folio_wait_writeback — literally just sit there and wait for a folio to finish its writeback era. 💅

🌸 SYNOPSIS 🌸

void folio_wait_writeback (struct folio *folio );

🎀 ARGUMENTS 🎀

• folio — the folio you're waiting on, aka the main character of this whole situation. 🦋

💖 DESCRIPTION 💖

So if the folio is currently in its "being written back to storage" phase, you wait for that I/O to complete. That's it. That's the whole vibe check. No cap, it's that simple. ✨

😴 CONTEXT 😴

Okay bestie, read this part carefully because it's giving important:

• It sleeps. Yes, fr fr, this one actually blocks. 😴
• It must be called in process context, and with no spinlocks held. Not negotiable, don't try it. 💀
• The caller should hold a reference on the folio. Hold onto your girl. 🫶
• And here's the little plot twist: if the folio is not locked, writeback may start again after writeback has finished. Like it said "I'm done" and then immediately got back in the group chat. 🙈 So lock it if you care about that.

🔥 SEE ALSO 🔥

Kernel file ./mm/page-writeback.c, plus this whole friend group of functions — go say hi to all of them, every single one, no skipping:

• node_dirtyable_memory(9)
• global_dirtyable_memory(9)
• domain_dirty_limits(9)
• global_dirty_limits(9)
• node_dirty_limit(9)
• node_dirty_ok(9)
• __wb_calc_thresh(9)
• balance_dirty_pages_ratelimited_flags(9)
• balance_dirty_pages_ratelimited(9)
• wb_over_bg_thresh(9)
• tag_pages_for_writeback(9)
• writeback_iter(9)
• filemap_dirty_folio(9)
• folio_redirty_for_writepage(9)
• folio_mark_dirty(9)
• folio_wait_writeback_killable(9)
• folio_wait_stable(9)

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Also: if you wanted the version of this that can be interrupted by a signal, that's folio_wait_writeback_killable(9) up there — she's built different. 👑

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And that's the whole page, bestie! 🧚 This icon of a manpage comes straight out of ./mm, dated October 2026 — slay, mark your calendars. 💜 Mwah, go wait on that writeback. 🌈⭐