__free_contig_range(9)

💖 __free_contig_range — Kernel API Manual ✨

Okay bestie, so this page is __free_contig_range(9) — like, the kernel API manual entry, and it's genuinely iconic once you get the vibe. Buckle up 🎀

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🌸 NAME 🌸

__free_contig_range — frees a contiguous range of order-0 pages. That's it, that's the whole girl. 💅

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✨ SYNOPSIS ✨

void __free_contig_range (unsigned long pfn , unsigned long nr_pages );

Like, no return value, it just goes in and does the thing 🫶

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🦋 ARGUMENTS 🦋

• pfn — the page frame number of the first page in the range. Like the starting address of the whole little squad, lowkey 🐾
• nr_pages — how many pages you're freeing. Count 'em. ✨

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💜 DESCRIPTION 💜

So for each order-0 struct page in that physically contiguous range, it puts a reference. And then — and this is the part — it frees any page whose reference count falls to zero. 💀 Love that for them.

And ngl the implementation is functionally equivalent to calling __free_page for each struct page in a loop, except it's significantly faster. Like, same result, way better performance. It ate, honestly. 🔥

Memory that was allocated with alloc_pages(order>=1) and then subsequently split to order-0 with split_page — that's the textbook example of appropriate contiguous pages you can free with this API. iykyk 💅

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⭐ CONTEXT ⭐

Okay so main character energy, but read the room:

• ✅ You may call it in interrupt context.
• ✅ You may call it while holding a normal spinlock.
• ❌ You may NOT call it in NMI context.
• ❌ You may NOT call it while holding a raw spinlock.

🚨 Bestie. Read the no-list again. NMI context and raw spinlocks are a hard no, fr fr. Do not test this. 🙈

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🎀 SEE ALSO 🎀

The kernel file lives at ./mm/page_alloc.c, and here's the whole friend group 🌈:

• __get_pfnblock_flags_mask(9)
• get_pfnblock_bit(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)
• 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)

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Sources and version check: this one comes out of ./mm, dated October 2026, and it's __free_contig_range(9) all the way down. Slay. 💖✨🦋