Documentation/filesystems/vfs.rst

Source file repositories/reference/linux-study-clean/Documentation/filesystems/vfs.rst

File Facts

System: Linux kernel
Corpus path: Documentation/filesystems/vfs.rst
Extension: .rst
Size: 61108 bytes
Lines: 1514
Domain: Support Tooling And Documentation
Bucket: Documentation
Inferred role: Support Tooling And Documentation: operation-table or driver-model contract
Status: pattern implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.
Defines an operation table; this is where Linux turns generic core objects into subsystem-specific behavior.
Uses kernel synchronization; read lock ordering, sleepability, and interrupt context assumptions before translating.
Allocates kernel memory; connect allocation flags and lifetime to context constraints.
Defines or uses C structs; map object ownership, embedded links, reference counts, and lock ownership.

Dependency Surface

linux/fs.h

Detected Declarations

struct file_system_type
struct super_operations
struct inode_operations
struct address_space_operations
struct file_operations
struct dentry_operations
function care

Annotated Snippet

struct file_operations
----------------------

This describes how the VFS can manipulate an open file.  As of kernel
4.18, the following members are defined:

.. code-block:: c

	struct file_operations {
		struct module *owner;
		fop_flags_t fop_flags;
		loff_t (*llseek) (struct file *, loff_t, int);
		ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
		ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
		ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
		ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
		int (*iopoll)(struct kiocb *kiocb, struct io_comp_batch *,
				unsigned int flags);
		int (*iterate_shared) (struct file *, struct dir_context *);
		__poll_t (*poll) (struct file *, struct poll_table_struct *);
		long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
		long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
		int (*mmap) (struct file *, struct vm_area_struct *);
		int (*open) (struct inode *, struct file *);
		int (*flush) (struct file *, fl_owner_t id);
		int (*release) (struct inode *, struct file *);
		int (*fsync) (struct file *, loff_t, loff_t, int datasync);
		int (*fasync) (int, struct file *, int);
		int (*lock) (struct file *, int, struct file_lock *);
		unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
		int (*check_flags)(int);
		int (*flock) (struct file *, int, struct file_lock *);
		ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
		ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
		void (*splice_eof)(struct file *file);
		int (*setlease)(struct file *, int, struct file_lease **, void **);
		long (*fallocate)(struct file *file, int mode, loff_t offset,
				  loff_t len);
		void (*show_fdinfo)(struct seq_file *m, struct file *f);
	#ifndef CONFIG_MMU
		unsigned (*mmap_capabilities)(struct file *);
	#endif
		ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
				loff_t, size_t, unsigned int);
		loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,
					   struct file *file_out, loff_t pos_out,
					   loff_t len, unsigned int remap_flags);
		int (*fadvise)(struct file *, loff_t, loff_t, int);
		int (*uring_cmd)(struct io_uring_cmd *ioucmd, unsigned int issue_flags);
		int (*uring_cmd_iopoll)(struct io_uring_cmd *, struct io_comp_batch *,
					unsigned int poll_flags);
		int (*mmap_prepare)(struct vm_area_desc *);
	};

Again, all methods are called without any locks being held, unless
otherwise noted.

``llseek``
	called when the VFS needs to move the file position index

``read``
	called by read(2) and related system calls

``read_iter``
	possibly asynchronous read with iov_iter as destination

``write``
	called by write(2) and related system calls

``write_iter``

Annotation

Immediate include surface: `linux/fs.h`.
Detected declarations: `struct file_system_type`, `struct super_operations`, `struct inode_operations`, `struct address_space_operations`, `struct file_operations`, `struct dentry_operations`, `function care`.
Atlas domain: Support Tooling And Documentation / Documentation.
Implementation status: pattern implementation candidate.
Synchronization appears in or near this file; preserve lock ordering, sleepability, and interrupt-context constraints.

Implementation Notes

This generated page is the file-by-file coverage layer; curated subsystem chapters should link here when they synthesize a multi-file control flow.
Core OS pages should be promoted from atlas-only to deep-reviewed when they explain data structures, invariants, locking, lifecycle, and C implementation snippets.
Driver-family pages are intentionally pattern-oriented unless they are part of the selected PCIe/NVMe representative device path.