STRUCT DEV_PAGEMAP(9)

👑 struct dev_pagemap(9) 👑

okay so this is a page out of the Kernel API Manual, and it's literally the blueprint for struct dev_pagemap — the metadata bestie for ZONE_DEVICE mappings. strap in 💖

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✨ NAME ✨

struct dev_pagemap — metadata for ZONE_DEVICE mappings. that's it, that's the vibe 🫶

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🌸 SYNOPSIS 🌸

here's the whole struct, character for character, no cap:

struct dev_pagemap {
    struct vmem_altmap altmap;
    struct percpu_ref ref;
    struct completion done;
    enum memory_type type;
    unsigned int flags;
    unsigned long vmemmap_shift;
    const struct dev_pagemap_ops *ops;
    void *owner;
    int nr_range;
    union {
      struct range range;
      struct range  ranges[];
    };
 };

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💅 Members 💅

every single field, explained, because we don't skip ✨

• altmap — pre-allocated/reserved memory for vmemmap allocations. it's the reserved little stash 🎀
• ref — reference count that pins the devm_memremap_pages mapping. keeps it alive, main character energy 🔥
• done — completion for ref. when ref is finished, this is how you know 👀
• type — memory type: see MEMORY_* above in memremap.h. iykyk 📖
• flags — PGMAP_* flags to specify defailed behavior. (their spelling, not mine bestie 💀)
• vmemmap_shift — structural definition of how the vmemmap page metadata is populated, specifically the metadata page order. a zero value (that's the default) uses base pages as the vmemmap metadata representation. a bigger value will set up compound struct pages of the requested order value. so like, order matters ⭐
• ops — method table. the whole friend group of functions 💜
• owner — an opaque pointer identifying the entity that manages this instance. used by various helpers to make sure that no foreign ZONE_DEVICE memory is accessed. protecting the group chat from randos 🙈
• nr_range — number of ranges to be mapped 🔢
• {unnamed_union} — anonymous. she has no name but she serves 👑
• range — range to be mapped when nr_range == 1 ☝️
• ranges — array of ranges to be mapped when nr_range > 1 🌈

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🦋 SEE ALSO 🦋

• Kernel file ./include/linux/memremap.h
• struct vmem_altmap(9)

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ngl, if you're poking at ZONE_DEVICE mappings without reading the members list first, that's a vibe check you will fail 😭 read them all, fr fr.

and that's the page, bestie 💖 this cutie came from ./include/linux, dated October 2026, straight out of the Kernel API Manual — struct dev_pagemap(9), periodt. 🎀✨