alloc_contig_frozen_range(9)

✨ alloc_contig_frozen_range ✨

okay so bestie, welcome to the alloc_contig_frozen_range page from the Kernel API Manual 💅 this is a level-9 manpage (9), so it's kernel-internal energy, not your cute little userland command. stay with me, it's gonna slay.

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🌸 NAME 🌸

alloc_contig_frozen_range — literally tries to allocate a given range of frozen pages 🧊✨

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🎀 SYNOPSIS 🎀

int alloc_contig_frozen_range (unsigned long start , unsigned long end ,
       acr_flags_t alloc_flags , gfp_t gfp_mask );

that's the whole signature, no cap. four args, one int coming back at you 🫶

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🦋 ARGUMENTS 🦋

• start — the start PFN you wanna allocate 👑
• end — the one-past-the-last PFN to allocate, so it's exclusive, iykyk 🎯
• alloc_flags — the allocation information, aka the vibes you're passing in 🌈
• gfp_mask — the GFP mask. important bestie: Node/zone/placement hints are ignored here. Only some action and reclaim modifiers are supported. And those reclaim modifiers? They control allocation behavior during compaction/migration/reclaim. periodt. 💀

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💖 DESCRIPTION 💖

okay so first thing's first: the PFN range does not have to be pageblock aligned, which is honestly so chill of it. but — and this is the vibe check — the PFN range must belong to a single zone. one zone. no mixing. 🙅‍♀️

the very first thing this routine does is attempt to MIGRATE_ISOLATE all pageblocks in the range. once they're isolated, the pageblocks should not be modified by others, like hello, they're in their alone era 🧚✨

then all the frozen pages which PFN is in [start, end) are allocated for the caller 💖 and they could be freed with free_contig_frozen_range — and free_frozen_pages also could be used to free compound frozen pages directly. two options, both iconic 🎀

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⭐ RETURN ⭐

zero on success 🎉 or a negative error code 😭

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👑 SEE ALSO 👑

the kernel file ./mm/page_alloc.c and honestly a whole friend group of functions:

• __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)
• __free_contig_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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💅 reminder bestie: the PFN range must belong to a single zone. that's not a suggestion, that's the rule.

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and that's the page!! huge shoutout to the ./mm directory for hosting this whole situation, and this edition is dated October 2026 🗓️✨ mwah, go allocate something iconic 🫶💖🌈