STRUCT FUSE_INODE(9)

💅 struct fuse_inode(9) — like, the FUSE inode page, bestie

okay so this is the kernel API manual page for struct fuse_inode(9), and no cap, it's literally the whole blueprint of a FUSE inode. every field, every lock, every little #ifdef — we're going through ALL of it. grab a snack 🍓

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✨ NAME ✨

struct fuse_inode — FUSE inode. that's the vibe. that's the whole name. iconic.

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🦋 SYNOPSIS 🦋

here's the struct in all its glory, copied exactly so you can trust me fr fr:

struct fuse_inode {
    struct inode inode;
    u64 nodeid;
    u64 nlookup;
    struct fuse_forget_link *forget;
    u64 i_time;
    u32 inval_mask;
    umode_t orig_i_mode;
    struct timespec64 i_btime;
    u64 orig_ino;
    u64 attr_version;
    union {
      struct {
        struct list_head write_files;
        struct list_head queued_writes;
        int writectr;
        int iocachectr;
        wait_queue_head_t page_waitq;
        wait_queue_head_t direct_io_waitq;
      };
      struct {
        bool cached;
        loff_t size;
        loff_t pos;
        u64 version;
        struct timespec64 mtime;
        int epoch;
        u64 iversion;
        spinlock_t lock;
      } rdc;
    };
    unsigned long state;
    struct mutex mutex;
    spinlock_t lock;
  #ifdef CONFIG_FUSE_DAX;
    struct fuse_inode_dax *dax;
  #endif;
    struct fuse_submount_lookup *submount_lookup;
  #ifdef CONFIG_FUSE_PASSTHROUGH;
    struct fuse_backing *fb;
  #endif;
    u8 cached_i_blkbits;
 };

look at that union. look at those #ifdefs. it's giving ✨structured✨

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🎀 Members 🎀

time for the field-by-field tour, bestie. every single one, no skipping 💖

• inode — the inode data itself. the main character, honestly 👑
• nodeid — a unique ID that identifies the inode between userspace and kernel. it's the inode's little passport 🛂
• nlookup — number of lookups on this inode. yes we're counting. we love accountability 💅
• forget — the request used for sending the FORGET message
• i_time — time in jiffies until the file attributes are valid ⏳
• inval_mask — which attributes are invalid
• orig_i_mode — the sticky bit in inode->i_mode may have been removed, so this preserves the original mode. preservation era 🫶
• i_btime — cache birthtime. it's giving birthday 🎂
• orig_ino — 64-bit inode number
• attr_version — version of last attribute change
• {unnamed_union} — anonymous. mysterious. lowkey main character energy 🙈
• {unnamed_struct} — anonymous again. the anonymity is the point ✨
• write_files — files usable in writepage. protected by fi->lock 🔒
• queued_writes — writepages pending on truncate or fsync
• writectr — number of sent writes; a negative bias (FUSE_NOWRITE) means more writes are blocked ⚠️
• iocachectr — number of files/maps using page cache
• page_waitq — waitq for writepage completion
• direct_io_waitq — waitq for direct-io completion
• rdc — readdir cache (directory only). directory girlies only 📁
• state — miscellaneous bits describing inode state
• mutex — lock for serializing lookup and readdir for back compatibility
• lock — lock to protect write-related fields
• dax — Dax specific inode data
• submount_lookup — submount specific lookup tracking
• fb — reference to backing file in passthrough mode
• cached_i_blkbits — the underlying inode->i_blkbits value will not be modified, so this preserves the blocksize specified by the server 🧚

ngl the lock situation here is a whole personality trait. mutex for lookup/readdir back compat, lock for write stuff, and write_files is protected by fi->lock. keep them straight, bestie 💀

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🌈 SEE ALSO 🌈

go read these next, iykwyk:

• Kernel file ./fs/fuse/fuse_i.h
• struct fuse_submount_lookup(9)
• struct fuse_file(9)
• struct fuse_conn(9)
• fuse_fill_super_common(9)
• fuse_mount_remove(9)
• fuse_ctl_add_conn(9)
• fuse_ctl_remove_conn(9)

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and that's the page!! 🫶 this whole thing lives over in ./fs/fuse, and it's dated October 2026, so like… future vibes ⭐ anyway bestie go forth and struct fuse_inode responsibly 💜🧚