for_each_fr...ange_reverse(9)

💅 for_each_fr...ange_reverse(9) 💅

okay so welcome to the Kernel API Manual, bestie — the for_each_fr...ange_reverse(9) page and yes the name is literally abbreviated with dots in the header, that's not a typo, that's just how the man page title renders. we move. 🦋

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✨ NAME ✨

for_each_free_mem_range_reverse — rev-iterate through free memblock areas 💖

like, you go through them backwards, it's giving reverse chronological but for memory regions.

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🌸 SYNOPSIS 🌸

for_each_free_mem_range_reverse (i , nid , flags , p_start , p_end ,
p_nid );

that's the whole call, keep the spacing exactly like that, no cap. ✨

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🎀 ARGUMENTS 🎀

• i — u64 used as loop variable. it's the little counter guy that just chugs along, being a loop variable, main character energy honestly. 🫶
• nid — node selector, and NUMA_NO_NODE means all nodes. so if you want everything everywhere, that's your girl. 👑
• flags — pick from blocks based on memory attributes. you're choosing which blocks qualify, based on their attributes, okurrr. 🌈
• p_start — ptr to phys_addr_t for start address of the range, and yes it can be NULL. no pressure. 🙈
• p_end — ptr to phys_addr_t for end address of the range, also can be NULL. equally chill. 🙈
• p_nid — ptr to int for nid of the range, and yep, can be NULL too. three for three, slay. 💜

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🦋 DESCRIPTION 🦋

so what it does: it walks over free areas of memblock — and "free" here means literally memory && !reserved, iykyk, not reserved, just memory — and it does that walk in reverse order. back it up, back it up. 🔥

and the cute part? it's available as soon as memblock is initialized. no waiting around, it's ready early, lowkey iconic. ⭐

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💀 SEE ALSO 💀

Kernel file ./include/linux/memblock.h, plus the whole friend group:

• enum memblock_flags(9)
• struct memblock_region(9)
• struct memblock_type(9)
• struct memblock(9)
• for_each_physmem_range(9)
• __for_each_mem_range(9)
• __for_each_mem_range_rev(9)
• for_each_mem_range(9)
• for_each_mem_range_rev(9)
• for_each_reserved_mem_range(9)
• for_each_mem_pfn_range(9)
• for_each_free_mem_range(9)
• memblock_set_current_limit(9)
• memblock_region_memory_base_pfn(9)
• memblock_region_memory_end_pfn(9)
• memblock_region_reserved_base_pfn(9)
• memblock_region_reserved_end_pfn(9)
• for_each_mem_region(9)
• for_each_reserved_mem_region(9)

that's a lot of friends and honestly? obsessed. 💅

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💖 cute little sign-off: this page lives at ./include/linux and it's dated October 2026, so yeah, timestamped and everything. go forth and rev-iterate, bestie. 🧚✨