VIDEOS 》 Linux Kernel FileSystems Subsystem

File system :: https://en.wikipedia.org/wiki/File_system
Linux Kernel Source:
/fs/filesystems.c :: http://elixir.free-electrons.com/linux/latest/source/fs/filesystems.c
register_filesystem(), unregister_filesystem() APIs :: http://elixir.free-electrons.com/linux/latest/source/fs/filesystems.c#L71
struct file_system_type data-structure :: http://elixir.free-electrons.com/linux/latest/source/include/linux/fs.h#L2068

Linux Kernel - ext4 filesystem type:
static struct file_system_type ext2_fs_type :: http://elixir.free-electrons.com/linux/latest/source/fs/ext4/super.c#L117
static struct file_system_type ext3_fs_type :: http://elixir.free-electrons.com/linux/latest/source/fs/ext4/super.c#L132
static struct file_system_type ext4_fs_type :: http://elixir.free-electrons.com/linux/latest/source/fs/ext4/super.c#L5774
static int __init ext4_init_fs(void) :: http://elixir.free-electrons.com/linux/latest/source/fs/ext4/super.c#L5786

Here is the register_filesystem(), unregister_filesystem() APIs (/fs/filesystems.c) from the Kernel-source version 4.14 for quick reference:

 *	register_filesystem - register a new filesystem
 *	@fs: the file system structure
 *	Adds the file system passed to the list of file systems the kernel
 *	is aware of for mount and other syscalls. Returns 0 on success,
 *	or a negative errno code on an error.
 *	The &struct file_system_type that is passed is linked into the kernel 
 *	structures and must not be freed until the file system has been
 *	unregistered.
int register_filesystem(struct file_system_type * fs)
	int res = 0;
	struct file_system_type ** p;

	BUG_ON(strchr(fs->name, '.'));
	if (fs->next)
		return -EBUSY;
	p = find_filesystem(fs->name, strlen(fs->name));
	if (*p)
		res = -EBUSY;
		*p = fs;
	return res;


 *	unregister_filesystem - unregister a file system
 *	@fs: filesystem to unregister
 *	Remove a file system that was previously successfully registered
 *	with the kernel. An error is returned if the file system is not found.
 *	Zero is returned on a success.
 *	Once this function has returned the &struct file_system_type structure
 *	may be freed or reused.
int unregister_filesystem(struct file_system_type * fs)
	struct file_system_type ** tmp;

	tmp = &file_systems;
	while (*tmp) {
		if (fs == *tmp) {
			*tmp = fs->next;
			fs->next = NULL;
			return 0;
		tmp = &(*tmp)->next;

	return -EINVAL;

Here is the struct file_system_type data-structure (/include/linux/fs.h) from the Kernel-source version 4.14 for quick reference:

struct file_system_type {
	const char *name;
	int fs_flags;
#define FS_REQUIRES_DEV		1 
#define FS_HAS_SUBTYPE		4
#define FS_USERNS_MOUNT		8	/* Can be mounted by userns root */
#define FS_RENAME_DOES_D_MOVE	32768	/* FS will handle d_move() during rename() internally. */
	struct dentry *(*mount) (struct file_system_type *, int,
		       const char *, void *);
	void (*kill_sb) (struct super_block *);
	struct module *owner;
	struct file_system_type * next;
	struct hlist_head fs_supers;

	struct lock_class_key s_lock_key;
	struct lock_class_key s_umount_key;
	struct lock_class_key s_vfs_rename_key;
	struct lock_class_key s_writers_key[SB_FREEZE_LEVELS];

	struct lock_class_key i_lock_key;
	struct lock_class_key i_mutex_key;
	struct lock_class_key i_mutex_dir_key;

Linux Kernel Source:
/fs/inode.c :: http://elixir.free-electrons.com/linux/latest/source/fs/inode.c
struct inode :: http://elixir.free-electrons.com/linux/latest/source/include/linux/fs.h#L570

Linux Kernel - filesystem type specific inode handlers:
/fs/ext4/inode.c :: http://elixir.free-electrons.com/linux/latest/source/fs/ext4/inode.c
/fs/btrfs/inode.c :: http://elixir.free-electrons.com/linux/latest/source/fs/btrfs/inode.c
/fs/ext2/inode.c :: http://elixir.free-electrons.com/linux/latest/source/fs/ext2/inode.c

Here is the struct inode (/include/linux/fs.h) from the Kernel-source version 4.14 for quick reference:

struct inode {
	umode_t			i_mode;
	unsigned short		i_opflags;
	kuid_t			i_uid;
	kgid_t			i_gid;
	unsigned int		i_flags;

	struct posix_acl	*i_acl;
	struct posix_acl	*i_default_acl;

	const struct inode_operations	*i_op;
	struct super_block	*i_sb;
	struct address_space	*i_mapping;

	void			*i_security;

	/* Stat data, not accessed from path walking */
	unsigned long		i_ino;
	 * Filesystems may only read i_nlink directly.  They shall use the
	 * following functions for modification:
	 *    (set|clear|inc|drop)_nlink
	 *    inode_(inc|dec)_link_count
	union {
		const unsigned int i_nlink;
		unsigned int __i_nlink;
	dev_t			i_rdev;
	loff_t			i_size;
	struct timespec		i_atime;
	struct timespec		i_mtime;
	struct timespec		i_ctime;
	spinlock_t		i_lock;	/* i_blocks, i_bytes, maybe i_size */
	unsigned short          i_bytes;
	unsigned int		i_blkbits;
	enum rw_hint		i_write_hint;
	blkcnt_t		i_blocks;

	seqcount_t		i_size_seqcount;

	/* Misc */
	unsigned long		i_state;
	struct rw_semaphore	i_rwsem;

	unsigned long		dirtied_when;	/* jiffies of first dirtying */
	unsigned long		dirtied_time_when;

	struct hlist_node	i_hash;
	struct list_head	i_io_list;	/* backing dev IO list */
	struct bdi_writeback	*i_wb;		/* the associated cgroup wb */

	/* foreign inode detection, see wbc_detach_inode() */
	int			i_wb_frn_winner;
	u16			i_wb_frn_avg_time;
	u16			i_wb_frn_history;
	struct list_head	i_lru;		/* inode LRU list */
	struct list_head	i_sb_list;
	struct list_head	i_wb_list;	/* backing dev writeback list */
	union {
		struct hlist_head	i_dentry;
		struct rcu_head		i_rcu;
	u64			i_version;
	atomic_t		i_count;
	atomic_t		i_dio_count;
	atomic_t		i_writecount;
	atomic_t		i_readcount; /* struct files open RO */
	const struct file_operations	*i_fop;	/* former ->i_op->default_file_ops */
	struct file_lock_context	*i_flctx;
	struct address_space	i_data;
	struct list_head	i_devices;
	union {
		struct pipe_inode_info	*i_pipe;
		struct block_device	*i_bdev;
		struct cdev		*i_cdev;
		char			*i_link;
		unsigned		i_dir_seq;

	__u32			i_generation;

	__u32			i_fsnotify_mask; /* all events this inode cares about */
	struct fsnotify_mark_connector __rcu	*i_fsnotify_marks;

	struct fscrypt_info	*i_crypt_info;

	void			*i_private; /* fs or device private pointer */
} __randomize_layout;

Virtual file system :: https://en.wikipedia.org/wiki/Virtual_file_system
Linux Kernel Storage Stack Diagram :: https://upload.wikimedia.org/wikipedia/commons/3/30/IO_stack_of_the_Linux_kernel.svg
Image - Linux Virtual File System :: https://www.ibm.com/developerworks/library/l-virtual-filesystem-switch/figure2.gif

Wiki - Linux Kernel Storage Stack Diagram
Linux Kernel Storage Stack Diagram
Image - Linux Virtual File System
Image - Linux Virtual File System

Virtual file system :: https://en.wikipedia.org/wiki/Virtual_file_system

Linux Kernel:
fs/namei.c - vfs_mknod(), vfs_mkdir(), vfs_rename() :: https://elixir.bootlin.com/linux/latest/source/fs/namei.c

Suggested Topics:

Video Episodes :: Linux Kernel programming

Linux Kernel Compilation ↗
Saturday' 13-Mar-2021

Linux Kernel /proc Interface ↗
Saturday' 13-Mar-2021

Linux Kernel Programming ↗
Saturday' 13-Mar-2021

Linux Kernel - Containers and Namespaces ↗
Saturday' 13-Mar-2021

Linux Operating System - User-space Processes ↗
Saturday' 13-Mar-2021

Linux Kernel Programming - Device Drivers ↗
Saturday' 13-Mar-2021
Watch detailed videos and read topics on Linux Kernel Programming - Device Drivers

Linux Kernel Architecture ↗
Saturday' 13-Mar-2021

Linux ioctl() API interface ↗
Saturday' 13-Mar-2021
Watch detailed videos and read topics on Linux Kernel Programming and Linux ioctl() API interface

Linux Kernel FileSystems Subsystem ↗
Saturday' 13-Mar-2021

Join The Linux Channel :: Facebook Group ↗

Visit The Linux Channel :: on Youtube ↗

💗 Help shape the future: Sponsor/Donate

Recommended Topics:
Featured Video:
Watch on Youtube - x22c Linux Kernel Programming | likely() & unlikely() ↗

Raspberry Pi OS with PIXEL ↗
Saturday' 13-Mar-2021

Programming Language Performance and Overheads ↗
Saturday' 13-Mar-2021
A detailed Youtube video series of various programming language performance and overheads - a big picture

What is a Linux Kernel Module - a Big Picture ↗
Saturday' 13-Mar-2021
Learning Linux Kernel Programming is always fascinating and yet challenging. So generally you may tend to learn Kernel Module programming, since such a module can be dynamically plugged into running Linux Kernel. But this will lead to confusion, and many assume kernel source is mostly a collection of these modules. Which in reality is not. Not just that, when we say Kernel Module, its a vaguely defined term. The term Module (as we know) is nothing but a collection of APIs, bunch of variables and associated data-structures. Which may or may not be a plugable kernel module. If you ask me, I am a fan of wiring Linux Kernel Modules, which may not be necessarily a pluggable kernel module. It all boils down to the address space at which these modules function inside a monolithic Linux Kernel. Which is nothing but Linux Kernel's address space. Hence here is my detailed multi-episode Youtube video series on Linux Kernel modules, a big picture and the significance of the

Linux Kernel Programming | with or without Kernel Modules | Device Drivers ↗
Saturday' 13-Mar-2021
When learning Linux Kernel programming, often I notice my students and viewers gets confused and they start with learning writing Linux Kernel modules. And so they develop the common misconception about Kernel Programming in general. They assume writing code in Linux Kernel means writing kernel modules. Which is absolutely not. Kernel modules are an optional choice and are part of Linux Kernel. But besides modules, Linux Kernel has lot of other mainstream code. Hence if anyone wants to be a Kernel Developer, you should be aware that sometimes you add new code via modules, sometimes without them. And if you ask me, I am not much in favor of writing Kernel modules. Instead in my code, I try to integrate and make them a part of Linux Kernel so that they all get initialized during boot time. Here is an extensive Youtube video of mine on Linux Kernel Programming, with and without Kernel Modules.

Weekly News Digest - Week 03 - June 2020 ↗
Saturday' 13-Mar-2021
The Linux Channel :: Weekly News Digest - Week 03 - June 2020 > KimĪ‡ Micro: A powerful alternative to the Raspberry Pi that supports PCIe cards > Linux Lands And Then Reverts Usage Of Flexible Array Members > AMD Ryzen 4000-Powered Asus Mini PC Challenges Intel's NUC > Aaeon's Raspberry Pi-like Board Bears An Intel 8th Gen Core i7 CPU and 16GB of DDR4 > Linus Torvalds Announces Massive Linux Kernel 5.8 Update > New Cisco Cloud Scale ASIC & 400G Line Card Announced > Key Differences of PoE vs PoE+ vs PoE++ Switches a STH Guide

CEO, CTO Talk ↗
Saturday' 13-Mar-2021

TCP vs UDP an Expert Opinion ↗
Saturday' 13-Mar-2021

Weekly News Digest - Week 5 - February 2018 ↗
Saturday' 13-Mar-2021
> Mini-ITX board fosters flexibility and fights obsolescence > You Can Do Better Than Arduino: Try These Microcontrollers > Open source is 20: How it changed programming and business forever > Since computer technology evolves so rapidly, does it matter if you have 5 or 15 years of experience as e.g. software developer? > Linux Kernel net_device data-structure - possible_net_t nd_net - Network namespace and Linux Containers - Ep7 > New Wave of Mini Satellites Could Boost Climate Research > Here come all the AI deployments; Now how do we manage AI? > Imagination announces neural network acceleration push

How to start Open-Source Project ↗
Saturday' 13-Mar-2021

Weekly News Digest - Week 8 - February 2018 ↗
Saturday' 13-Mar-2021
> Asymmetric Processor Cores > Using QCT Quanta LB6M 10GbE Switch for Container Networking > Using SSE Instead Of WebSockets For Unidirectional Data Flow Over HTTP/2 > Why IPv6 networks create DNS configuration problems > Hypervisor or containers: Which solution is right for you? > Blockchain for 2018 and Beyond: A (growing) list of blockchain use cases > Raw sockets backdoor gives attackers complete control of some Linux servers

Trending Video:
Watch on Youtube - 352 Linux user-space - Shared Memory IPC - Live Demo and Exa ↗

Linux Kernel dst_entry data-structure ↗
Saturday' 13-Mar-2021

Recommended Video:
Watch on Youtube - x224 Linux Kernel Dummy Network Interface /drivers/net/dummy... ↗