get_pfnblock_bit(9)

🌸 get_pfnblock_bit(9) — kernel API manual, but make it make sense 🌸

okay bestie, so this one is from the kernel API manual (get_pfnblock_bit(9), section 9, we stan a numbered manual section) and it's genuinely one of the smaller little guys in ./mm, so let's get into it 💅

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✨ NAME ✨

get_pfnblock_bit — the "is this one single standalone bit of a pageblock actually set?" check 🔍

🦋 SYNOPSIS 🦋

bool get_pfnblock_bit (const struct page *page , unsigned long pfn ,
enum pageblock_bits pb_bit );

like, yes, that's the whole signature, keep it exactly as-is, no notes 🫶

🎀 ARGUMENTS 🎀

• page — const struct page * — the page that lives inside the block you care about, iykyk 🏠
• pfn — unsigned long — the target page frame number, aka the exact frame you're pointing at 🎯
• pb_bit — enum pageblock_bits — which pageblock bit you wanna check 👀

⭐ RETURN ⭐

• true if the bit is set 💖
• otherwise false 💀

that's it. that's the whole return contract. no cap.

🌈 SEE ALSO 🌈

so this function does NOT live alone, it has a whole friend group, and the kernel file it hangs out in is ./mm/page_alloc.c — here's everyone 👑

• __get_pfnblock_flags_mask(9)
• get_pfnblock_migratetype(9)
• __set_pfnblock_flags_mask(9)
• set_pfnblock_bit(9)
• clear_pfnblock_bit(9)
• set_pageblock_migratetype(9)
• __move_freepages_block_isolate(9)
• __putback_isolated_page(9)
• __free_pages(9)
• free_pages(9)
• alloc_pages_exact(9)
• alloc_pages_exact_nid(9)
• free_pages_exact(9)
• nr_free_zone_pages(9)
• nr_free_buffer_pages(9)
• find_next_best_node(9)
• free_reserved_pages(9)
• setup_per_zone_wmarks(9)
• __free_contig_range(9)
• alloc_contig_frozen_range(9)
• alloc_contig_range(9)
• alloc_contig_frozen_pages(9)
• alloc_contig_pages(9)
• free_contig_frozen_range(9)
• free_contig_range(9)
• alloc_pages_nolock(9)

bestie reminder: every one of those is literally spelled the same in the real page, so don't go "fixing" the underscores, the double underscores mean something 🙈

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and that's the whole vibe check 💜 this page came from ./mm and it's dated October 2026, so go off, read the source, slay, periodt ✨🎀🦋