drbd_bitmap_io(9)

💅 drbd_bitmap_io(9) — the Kernel API Manual page you didn't know you needed ✨

okay so bestie, sit down, grab a strawberry 🍓, because we're about to talk about drbd_bitmap_io(9) — yes it's a kernel function, yes it's from the Kernel API Manual, and yes it's kind of iconic in a "does one very specific job" way 👑

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🌸 NAME 🌸

drbd_bitmap_io — does an IO operation on the whole bitmap. that's it, that's the vibe. whole bitmap, one IO op, no cap 💅

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🦋 SYNOPSIS 🦋

int drbd_bitmap_io (struct drbd_device *device , int (*io_fn)(struct
drbd_device *, struct drbd_peer_device *) , char *why , enum bm_flag
flags , struct drbd_peer_device *peer_device );

like look at this signature, it's so extra and we love that for it 💖

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🎀 ARGUMENTS 🎀

• device — the DRBD device. your main character ✨
• io_fn — the IO callback, the little function that gets called when bitmap IO is actually possible. it's giving "waiting for its moment" 🧚
• why — descriptive text explaining the reason for doing the IO. literally just the receipts of why we're here 📝
• flags — bitmap flags. 🚩
• peer_device — the peer DRBD device. the plus-one to device 🫶

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🔥 DESCRIPTION 🔥

so what it does: it freezes application IO while the actual IO operations run. yes, freezes. like hitting pause on a Netflix binge 😭

⚠️ okay this is the important part, bestie — this function MAY NOT be called from worker context. not optional, not "probably fine", not "just this once". periodt. 💀

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🌈 SEE ALSO 🌈

the whole friend group, in the kernel file ./drivers/block/drbd/drbd_main.c:

• tl_release(9)
• _tl_restart(9)
• tl_clear(9)
• tl_abort_disk_io(9)
• drbd_thread_current_set_cpu(9)
• drbd_send_current_state(9)
• drbd_send_state(9)
• _drbd_send_ack(9)
• drbd_send_ack(9)
• drbd_md_sync(9)
• drbd_md_read(9)
• drbd_md_mark_dirty(9)
• drbd_uuid_new_current(9)
• drbd_bmio_set_n_write(9)
• drbd_bmio_clear_n_write(9)
• drbd_queue_bitmap_io(9)
• drbd_wait_misc(9)

go read them, iykyk 📚💜

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⭐ the cute sign-off ⭐

this little icon lives in ./drivers/block/drbd, dated October 2026, and it's titled drbd_bitmap_io(9) — so yeah, that's the whole page. slay, stay hydrated, and don't call it from worker context bestie 💖✨🎀