pfn_valid(9)

✨ pfn_valid ✨

okay so bestie, this is a kernel API manual page and we're about to get so into it 💅

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🌸 NAME 🌸

pfn_valid — check if there is a valid memory map entry for a PFN

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🦋 SYNOPSIS 🦋

int pfn_valid (unsigned long pfn );

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🎀 ARGUMENTS 🎀

• pfn — the page frame number to check, like the scrunchie you're looking for in your bag 🔍

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💖 DESCRIPTION 💖

So basically, this function checks if there is a valid memory map entry — aka a struct page — for the pfn. it's giving "do you have a valid ID" energy at the kernel club 🪪✨

⚠️ but bestie, listen: just because the memory map entry exists does not mean there's actual usable memory at that pfn. the struct page might be representing a hole or an unusable page frame. so like… it's valid but it's not valid valid, y'know? no cap, this is important 💀

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🔥 RETURN 🔥

1 for PFNs that have memory map entries, and 0 otherwise. periodt. 💯

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🌈 SEE ALSO 🌈

The kernel file ./include/linux/mmzone.h is the main character here, and the squad includes:

• is_highmem(9)
• for_each_online_pgdat(9)
• for_each_zone(9)
• next_zones_zonelist(9)
• first_zones_zonelist(9)
• for_each_zone_zonelist_nodemask(9)
• for_each_zone_zonelist(9)

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okay that's the whole vibe bestie, hope you slayed this and understood it fr fr 💜✨

catch you in the ./include/linux directory, October 2026 edition, version pfn_valid(9) 🫶🎀