balance_dir...imited_flags(9)

💅 balance_dirty_pages_ratelimited_flags — a Kernel API Manual moment ✨

okay so before we even start, bestie, this is a page from the Kernel API Manual, section 9, and the star of the show is balance_dirty_pages_ratelimited_flags — yes the name is a whole entire mouthful, we love her anyway 🎀

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✨ NAME ✨

balance_dirty_pages_ratelimited_flags — literally just Balance dirty memory state. that's it, that's the elevator pitch 🫶

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🌸 SYNOPSIS 🌸

int balance_dirty_pages_ratelimited_flags (struct address_space *mapping
, unsigned int flags );

like, she takes a mapping and some flags and hands you back an int. iconic signature ngl 💅

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🦋 ARGUMENTS 🦋

• mapping — the address_space which was dirtied. that's the vibe, that's the thing you got messy 🍓
• flags — BDP flags. yes they're just called BDP flags, no further notes, we move 😭

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💖 DESCRIPTION 💖

so here's the tea. any process that's dirtying memory should call in here once for each page which was newly dirtied. one call, one freshly-dirtied page, that's the deal fr fr.

and then? the function will periodically check the system's dirty state and will initiate writeback if needed. she's like a little roomba for your dirty pages, checking in on a schedule, kicking off writeback when things get too messy ✨

also, heads up bestie — the manpage says to see balance_dirty_pages_ratelimited for details, so if you want the full lore, that's where it's at 👑

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🌈 RETURN 🌈

okay so this is where it actually matters, pay attention 💀

• if flags contains BDP_ASYNC, she may return -EAGAIN — which is the code for "memory is out of balance and the caller must wait for I/O to complete". so like, you gotta go wait, no cutting the line 🙈
• otherwise, she returns 0 — and that 0 means either memory was already in balance, or she was able to sleep until the amount of dirty memory returned to balance. either way, balanced, slay, we love a clean exit 🎀

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⭐ SEE ALSO ⭐

she lives in the kernel file ./mm/page-writeback.c and she has a whole friend group, look at this roster 🔥

• 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(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(9)
• folio_wait_writeback_killable(9)
• folio_wait_stable(9)

all of them are (9) girls, we stan a consistent section number 💜

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💀 tiny reminder that this is all coming at you from ./mm, dated October 2026, so go read the source if you need more, bestie.

mwah, go balance some dirty pages, ily, bye 🧚💖