Data models

A condensed reference of the major in-kernel objects and how they relate. Use this page as a "where to look" rather than a definition. Each link below points at the header where the structure is declared.

Process / thread

graph LR
    TASK[task_struct] -->|"->mm"| MM[mm_struct]
    TASK -->|"->files"| FILES[files_struct]
    TASK -->|"->fs"| FS[fs_struct]
    TASK -->|"->signal, ->sighand"| SIG[signal_struct, sighand_struct]
    TASK -->|"->cred"| CRED[cred]
    TASK -->|"->se / ->dl / ->rt"| SCHED[sched_entity / sched_dl_entity / sched_rt_entity]
    TASK -->|"->nsproxy"| NS[nsproxy]
    NS -->|"net/uts/ipc/pid/mnt/cgroup/time"| NSITEMS[per-namespace structs]
    MM --> VMA[vm_area_struct *]
    MM -->|maple tree| MT[mt_root]
    FILES --> FDT[fdtable]
    FDT --> FILE[struct file *]

Object	Header	Notes
task_struct	include/linux/sched.h	Thread descriptor; one per kernel thread or user thread.
mm_struct	include/linux/mm_types.h	Address space. Shared between threads of one process.
vm_area_struct	include/linux/mm_types.h	A contiguous virtual range with one set of permissions.
cred	include/linux/cred.h	uid/gid/caps and security blob.
signal_struct, sighand_struct	include/linux/sched/signal.h	Per-thread-group and per-thread-handler signal state.
nsproxy	include/linux/nsproxy.h	Per-process namespace bundle.
files_struct, fdtable	include/linux/fdtable.h	The file-descriptor table.
pid, pid_namespace	include/linux/pid.h, include/linux/pid_namespace.h	Numeric pid in a hierarchical pid namespace.

Filesystems / VFS

Object	Header
super_block	include/linux/fs.h
inode	include/linux/fs.h
dentry	include/linux/dcache.h
file	include/linux/fs.h
address_space	include/linux/fs.h
folio	include/linux/mm_types.h
path	include/linux/path.h
vfsmount	include/linux/mount.h
file_system_type	include/linux/fs.h

Operations vtables: super_operations, inode_operations, dentry_operations, file_operations, address_space_operations (all in include/linux/fs.h).

Block

Object	Header
bio, bvec_iter	include/linux/blk_types.h
request, request_queue	include/linux/blkdev.h
gendisk, block_device	include/linux/blkdev.h
blk_mq_tag_set, blk_mq_hw_ctx	include/linux/blk-mq.h

Networking

Object	Header
net_device	include/linux/netdevice.h
sk_buff	include/linux/skbuff.h
sock, socket, proto, proto_ops	include/net/sock.h, include/linux/net.h
net (namespace)	include/net/net_namespace.h
fib_table, fib_rules	include/net/fib_rules.h
neighbour	include/net/neighbour.h
inet_sock, tcp_sock, udp_sock	include/net/inet_sock.h, tcp.h, udp.h

Device model

Object	Header
device, device_driver, bus_type, class	include/linux/device.h
kobject, kset, kref, kobj_type	include/linux/kobject.h
pci_dev, pci_driver	include/linux/pci.h
usb_device, usb_driver, usb_interface	include/linux/usb.h
platform_device, platform_driver	include/linux/platform_device.h

Synchronization

Primitive	Header
spinlock_t, rwlock_t	include/linux/spinlock.h
mutex	include/linux/mutex.h
rw_semaphore	include/linux/rwsem.h
seqlock_t, seqcount_t	include/linux/seqlock.h
completion	include/linux/completion.h
wait_queue_head_t, wait_event_*	include/linux/wait.h
atomic_t, atomic64_t	include/linux/atomic.h
refcount_t	include/linux/refcount.h
RCU API	include/linux/rcupdate.h

Memory

Object	Header
page	include/linux/mm_types.h
folio	same
pgd_t, p4d_t, pud_t, pmd_t, pte_t	arch/<arch>/include/asm/pgtable.h
kmem_cache	include/linux/slab.h
mempool_t	include/linux/mempool.h
iov_iter	include/linux/uio.h
gfp_t	include/linux/gfp.h

Cgroups

Object	Header
cgroup_subsys_state	include/linux/cgroup-defs.h
cgroup, cgroup_root	same
css_set, cgrp_cset_link	same
cgroup_subsys	same

BPF

Object	Header
bpf_prog, bpf_insn	include/linux/bpf.h, include/linux/filter.h
bpf_map	include/linux/bpf.h
bpf_link	include/linux/bpf.h
BTF types	include/linux/btf.h

Related pages

• Architecture — high-level system layering.
• Subsystems — per-area depth.
• Glossary — vocabulary.