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FUSE: Filesystem in Userspace
Copyright (C) 2001-2008 Miklos Szeredi <>
This program can be distributed under the terms of the GNU GPL.
See the file COPYING.
#ifndef _FS_FUSE_I_H
#define _FS_FUSE_I_H
#include <linux/fuse.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/wait.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/backing-dev.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/rbtree.h>
#include <linux/poll.h>
#include <linux/workqueue.h>
/** Max number of pages that can be used in a single read request */
/** Bias for fi->writectr, meaning new writepages must not be sent */
/** It could be as large as PATH_MAX, but would that have any uses? */
#define FUSE_NAME_MAX 1024
/** Number of dentries for each connection in the control filesystem */
/** If the FUSE_DEFAULT_PERMISSIONS flag is given, the filesystem
module will check permissions based on the file mode. Otherwise no
permission checking is done in the kernel */
/** If the FUSE_ALLOW_OTHER flag is given, then not only the user
doing the mount will be allowed to access the filesystem */
#define FUSE_ALLOW_OTHER (1 << 1)
/** Number of page pointers embedded in fuse_req */
/** List of active connections */
extern struct list_head fuse_conn_list;
/** Global mutex protecting fuse_conn_list and the control filesystem */
extern struct mutex fuse_mutex;
/** Module parameters */
extern unsigned max_user_bgreq;
extern unsigned max_user_congthresh;
/* One forget request */
struct fuse_forget_link {
struct fuse_forget_one forget_one;
struct fuse_forget_link *next;
/** FUSE inode */
struct fuse_inode {
/** Inode data */
struct inode inode;
/** Unique ID, which identifies the inode between userspace
* and kernel */
u64 nodeid;
/** Number of lookups on this inode */
u64 nlookup;
/** The request used for sending the FORGET message */
struct fuse_forget_link *forget;
/** Time in jiffies until the file attributes are valid */
u64 i_time;
/** The sticky bit in inode->i_mode may have been removed, so
preserve the original mode */
umode_t orig_i_mode;
/** 64 bit inode number */
u64 orig_ino;
/** Version of last attribute change */
u64 attr_version;
/** Files usable in writepage. Protected by fc->lock */
struct list_head write_files;
/** Writepages pending on truncate or fsync */
struct list_head queued_writes;
/** Number of sent writes, a negative bias (FUSE_NOWRITE)
* means more writes are blocked */
int writectr;
/** Waitq for writepage completion */
wait_queue_head_t page_waitq;
/** List of writepage requestst (pending or sent) */
struct list_head writepages;
/** Miscellaneous bits describing inode state */
unsigned long state;
/** FUSE inode state bits */
enum {
/** Advise readdirplus */
/** Initialized with readdirplus */
/** An operation changing file size is in progress */
struct fuse_conn;
/** FUSE specific file data */
struct fuse_file {
/** Fuse connection for this file */
struct fuse_conn *fc;
/** Request reserved for flush and release */
struct fuse_req *reserved_req;
/** Kernel file handle guaranteed to be unique */
u64 kh;
/** File handle used by userspace */
u64 fh;
/** Node id of this file */
u64 nodeid;
/** Refcount */
atomic_t count;
/** FOPEN_* flags returned by open */
u32 open_flags;
/** Entry on inode's write_files list */
struct list_head write_entry;
/** RB node to be linked on fuse_conn->polled_files */
struct rb_node polled_node;
/** Wait queue head for poll */
wait_queue_head_t poll_wait;
/** Has flock been performed on this file? */
bool flock:1;
/** One input argument of a request */
struct fuse_in_arg {
unsigned size;
const void *value;
/** The request input */
struct fuse_in {
/** The request header */
struct fuse_in_header h;
/** True if the data for the last argument is in req->pages */
unsigned argpages:1;
/** Number of arguments */
unsigned numargs;
/** Array of arguments */
struct fuse_in_arg args[3];
/** One output argument of a request */
struct fuse_arg {
unsigned size;
void *value;
/** The request output */
struct fuse_out {
/** Header returned from userspace */
struct fuse_out_header h;
* The following bitfields are not changed during the request
* processing
/** Last argument is variable length (can be shorter than
arg->size) */
unsigned argvar:1;
/** Last argument is a list of pages to copy data to */
unsigned argpages:1;
/** Zero partially or not copied pages */
unsigned page_zeroing:1;
/** Pages may be replaced with new ones */
unsigned page_replace:1;
/** Number or arguments */
unsigned numargs;
/** Array of arguments */
struct fuse_arg args[2];
/** FUSE page descriptor */
struct fuse_page_desc {
unsigned int length;
unsigned int offset;
struct fuse_args {
struct {
struct {
uint32_t opcode;
uint64_t nodeid;
} h;
unsigned numargs;
struct fuse_in_arg args[3];
} in;
struct {
unsigned argvar:1;
unsigned numargs;
struct fuse_arg args[2];
} out;
#define FUSE_ARGS(args) struct fuse_args args = {}
/** The request state */
enum fuse_req_state {
/** The request IO state (for asynchronous processing) */
struct fuse_io_priv {
int async;
spinlock_t lock;
unsigned reqs;
ssize_t bytes;
size_t size;
__u64 offset;
bool write;
int err;
struct kiocb *iocb;
struct file *file;
* A request to the client
struct fuse_req {
/** This can be on either pending processing or io lists in
fuse_conn */
struct list_head list;
/** Entry on the interrupts list */
struct list_head intr_entry;
/** refcount */
atomic_t count;
/** Unique ID for the interrupt request */
u64 intr_unique;
* The following bitfields are either set once before the
* request is queued or setting/clearing them is protected by
* fuse_conn->lock
/** True if the request has reply */
unsigned isreply:1;
/** Force sending of the request even if interrupted */
unsigned force:1;
/** The request was aborted */
unsigned aborted:1;
/** Request is sent in the background */
unsigned background:1;
/** The request has been interrupted */
unsigned interrupted:1;
/** Data is being copied to/from the request */
unsigned locked:1;
/** Request is counted as "waiting" */
unsigned waiting:1;
/** State of the request */
enum fuse_req_state state;
/** The request input */
struct fuse_in in;
/** The request output */
struct fuse_out out;
/** Used to wake up the task waiting for completion of request*/
wait_queue_head_t waitq;
/** Data for asynchronous requests */
union {
struct {
struct fuse_release_in in;
struct inode *inode;
} release;
struct fuse_init_in init_in;
struct fuse_init_out init_out;
struct cuse_init_in cuse_init_in;
struct {
struct fuse_read_in in;
u64 attr_ver;
} read;
struct {
struct fuse_write_in in;
struct fuse_write_out out;
struct fuse_req *next;
} write;
struct fuse_notify_retrieve_in retrieve_in;
} misc;
/** page vector */
struct page **pages;
/** page-descriptor vector */
struct fuse_page_desc *page_descs;
/** size of the 'pages' array */
unsigned max_pages;
/** inline page vector */
struct page *inline_pages[FUSE_REQ_INLINE_PAGES];
/** inline page-descriptor vector */
struct fuse_page_desc inline_page_descs[FUSE_REQ_INLINE_PAGES];
/** number of pages in vector */
unsigned num_pages;
/** File used in the request (or NULL) */
struct fuse_file *ff;
/** Inode used in the request or NULL */
struct inode *inode;
/** AIO control block */
struct fuse_io_priv *io;
/** Link on fi->writepages */
struct list_head writepages_entry;
/** Request completion callback */
void (*end)(struct fuse_conn *, struct fuse_req *);
/** Request is stolen from fuse_file->reserved_req */
struct file *stolen_file;
* A Fuse connection.
* This structure is created, when the filesystem is mounted, and is
* destroyed, when the client device is closed and the filesystem is
* unmounted.
struct fuse_conn {
/** Lock protecting accessess to members of this structure */
spinlock_t lock;
/** Refcount */
atomic_t count;
struct rcu_head rcu;
/** The user id for this mount */
kuid_t user_id;
/** The group id for this mount */
kgid_t group_id;
/** The fuse mount flags for this mount */
unsigned flags;
/** Maximum read size */
unsigned max_read;
/** Maximum write size */
unsigned max_write;
/** Readers of the connection are waiting on this */
wait_queue_head_t waitq;
/** The list of pending requests */
struct list_head pending;
/** The list of requests being processed */
struct list_head processing;
/** The list of requests under I/O */
struct list_head io;
/** The next unique kernel file handle */
u64 khctr;
/** rbtree of fuse_files waiting for poll events indexed by ph */
struct rb_root polled_files;
/** Maximum number of outstanding background requests */
unsigned max_background;
/** Number of background requests at which congestion starts */
unsigned congestion_threshold;
/** Number of requests currently in the background */
unsigned num_background;
/** Number of background requests currently queued for userspace */
unsigned active_background;
/** The list of background requests set aside for later queuing */
struct list_head bg_queue;
/** Pending interrupts */
struct list_head interrupts;
/** Queue of pending forgets */
struct fuse_forget_link forget_list_head;
struct fuse_forget_link *forget_list_tail;
/** Batching of FORGET requests (positive indicates FORGET batch) */
int forget_batch;
/** Flag indicating that INIT reply has been received. Allocating
* any fuse request will be suspended until the flag is set */
int initialized;
/** Flag indicating if connection is blocked. This will be
the case before the INIT reply is received, and if there
are too many outstading backgrounds requests */
int blocked;
/** waitq for blocked connection */
wait_queue_head_t blocked_waitq;
/** waitq for reserved requests */
wait_queue_head_t reserved_req_waitq;
/** The next unique request id */
u64 reqctr;
/** Connection established, cleared on umount, connection
abort and device release */
unsigned connected;
/** Connection failed (version mismatch). Cannot race with
setting other bitfields since it is only set once in INIT
reply, before any other request, and never cleared */
unsigned conn_error:1;
/** Connection successful. Only set in INIT */
unsigned conn_init:1;
/** Do readpages asynchronously? Only set in INIT */
unsigned async_read:1;
/** Do not send separate SETATTR request before open(O_TRUNC) */
unsigned atomic_o_trunc:1;
/** Filesystem supports NFS exporting. Only set in INIT */
unsigned export_support:1;
/** Set if bdi is valid */
unsigned bdi_initialized:1;
/** write-back cache policy (default is write-through) */
unsigned writeback_cache:1;
* The following bitfields are only for optimization purposes
* and hence races in setting them will not cause malfunction
/** Is open/release not implemented by fs? */
unsigned no_open:1;
/** Is fsync not implemented by fs? */
unsigned no_fsync:1;
/** Is fsyncdir not implemented by fs? */
unsigned no_fsyncdir:1;
/** Is flush not implemented by fs? */
unsigned no_flush:1;
/** Is setxattr not implemented by fs? */
unsigned no_setxattr:1;
/** Is getxattr not implemented by fs? */
unsigned no_getxattr:1;
/** Is listxattr not implemented by fs? */
unsigned no_listxattr:1;
/** Is removexattr not implemented by fs? */
unsigned no_removexattr:1;
/** Are posix file locking primitives not implemented by fs? */
unsigned no_lock:1;
/** Is access not implemented by fs? */
unsigned no_access:1;
/** Is create not implemented by fs? */
unsigned no_create:1;
/** Is interrupt not implemented by fs? */
unsigned no_interrupt:1;
/** Is bmap not implemented by fs? */
unsigned no_bmap:1;
/** Is poll not implemented by fs? */
unsigned no_poll:1;
/** Do multi-page cached writes */
unsigned big_writes:1;
/** Don't apply umask to creation modes */
unsigned dont_mask:1;
/** Are BSD file locking primitives not implemented by fs? */
unsigned no_flock:1;
/** Is fallocate not implemented by fs? */
unsigned no_fallocate:1;
/** Is rename with flags implemented by fs? */
unsigned no_rename2:1;
/** Use enhanced/automatic page cache invalidation. */
unsigned auto_inval_data:1;
/** Does the filesystem support readdirplus? */
unsigned do_readdirplus:1;
/** Does the filesystem want adaptive readdirplus? */
unsigned readdirplus_auto:1;
/** Does the filesystem support asynchronous direct-IO submission? */
unsigned async_dio:1;
/** The number of requests waiting for completion */
atomic_t num_waiting;
/** Negotiated minor version */
unsigned minor;
/** Backing dev info */
struct backing_dev_info bdi;
/** Entry on the fuse_conn_list */
struct list_head entry;
/** Device ID from super block */
dev_t dev;
/** Dentries in the control filesystem */
struct dentry *ctl_dentry[FUSE_CTL_NUM_DENTRIES];
/** number of dentries used in the above array */
int ctl_ndents;
/** O_ASYNC requests */
struct fasync_struct *fasync;
/** Key for lock owner ID scrambling */
u32 scramble_key[4];
/** Reserved request for the DESTROY message */
struct fuse_req *destroy_req;
/** Version counter for attribute changes */
u64 attr_version;
/** Called on final put */
void (*release)(struct fuse_conn *);
/** Super block for this connection. */
struct super_block *sb;
/** Read/write semaphore to hold when accessing sb. */
struct rw_semaphore killsb;
static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)
return sb->s_fs_info;
static inline struct fuse_conn *get_fuse_conn(struct inode *inode)
return get_fuse_conn_super(inode->i_sb);
static inline struct fuse_inode *get_fuse_inode(struct inode *inode)
return container_of(inode, struct fuse_inode, inode);
static inline u64 get_node_id(struct inode *inode)
return get_fuse_inode(inode)->nodeid;
/** Device operations */
extern const struct file_operations fuse_dev_operations;
extern const struct dentry_operations fuse_dentry_operations;
* Inode to nodeid comparison.
int fuse_inode_eq(struct inode *inode, void *_nodeidp);
* Get a filled in inode
struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
int generation, struct fuse_attr *attr,
u64 attr_valid, u64 attr_version);
int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
struct fuse_entry_out *outarg, struct inode **inode);
* Send FORGET command
void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
u64 nodeid, u64 nlookup);
struct fuse_forget_link *fuse_alloc_forget(void);
/* Used by READDIRPLUS */
void fuse_force_forget(struct file *file, u64 nodeid);
* Initialize READ or READDIR request
void fuse_read_fill(struct fuse_req *req, struct file *file,
loff_t pos, size_t count, int opcode);
* Send OPEN or OPENDIR request
int fuse_open_common(struct inode *inode, struct file *file, bool isdir);
struct fuse_file *fuse_file_alloc(struct fuse_conn *fc);
struct fuse_file *fuse_file_get(struct fuse_file *ff);
void fuse_file_free(struct fuse_file *ff);
void fuse_finish_open(struct inode *inode, struct file *file);
void fuse_sync_release(struct fuse_file *ff, int flags);
* Send RELEASE or RELEASEDIR request
void fuse_release_common(struct file *file, int opcode);
* Send FSYNC or FSYNCDIR request
int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
int datasync, int isdir);
* Notify poll wakeup
int fuse_notify_poll_wakeup(struct fuse_conn *fc,
struct fuse_notify_poll_wakeup_out *outarg);
* Initialize file operations on a regular file
void fuse_init_file_inode(struct inode *inode);
* Initialize inode operations on regular files and special files
void fuse_init_common(struct inode *inode);
* Initialize inode and file operations on a directory
void fuse_init_dir(struct inode *inode);
* Initialize inode operations on a symlink
void fuse_init_symlink(struct inode *inode);
* Change attributes of an inode
void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
u64 attr_valid, u64 attr_version);
void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
u64 attr_valid);
* Initialize the client device
int fuse_dev_init(void);
* Cleanup the client device
void fuse_dev_cleanup(void);
int fuse_ctl_init(void);
void __exit fuse_ctl_cleanup(void);
* Allocate a request
struct fuse_req *fuse_request_alloc(unsigned npages);
struct fuse_req *fuse_request_alloc_nofs(unsigned npages);
* Free a request
void fuse_request_free(struct fuse_req *req);
* Get a request, may fail with -ENOMEM,
* caller should specify # elements in req->pages[] explicitly
struct fuse_req *fuse_get_req(struct fuse_conn *fc, unsigned npages);
struct fuse_req *fuse_get_req_for_background(struct fuse_conn *fc,
unsigned npages);
* Increment reference count on request
void __fuse_get_request(struct fuse_req *req);
* Gets a requests for a file operation, always succeeds
struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
struct file *file);
* Decrement reference count of a request. If count goes to zero free
* the request.
void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req);
* Send a request (synchronous)
void fuse_request_send(struct fuse_conn *fc, struct fuse_req *req);
* Simple request sending that does request allocation and freeing
ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args);
* Send a request in the background
void fuse_request_send_background(struct fuse_conn *fc, struct fuse_req *req);
void fuse_request_send_background_locked(struct fuse_conn *fc,
struct fuse_req *req);
/* Abort all requests */
void fuse_abort_conn(struct fuse_conn *fc);
* Invalidate inode attributes
void fuse_invalidate_attr(struct inode *inode);
void fuse_invalidate_entry_cache(struct dentry *entry);
void fuse_invalidate_atime(struct inode *inode);
* Acquire reference to fuse_conn
struct fuse_conn *fuse_conn_get(struct fuse_conn *fc);
* Initialize fuse_conn
void fuse_conn_init(struct fuse_conn *fc);
* Release reference to fuse_conn
void fuse_conn_put(struct fuse_conn *fc);
* Add connection to control filesystem
int fuse_ctl_add_conn(struct fuse_conn *fc);
* Remove connection from control filesystem
void fuse_ctl_remove_conn(struct fuse_conn *fc);
* Is file type valid?
int fuse_valid_type(int m);
* Is current process allowed to perform filesystem operation?
int fuse_allow_current_process(struct fuse_conn *fc);
u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id);
int fuse_update_attributes(struct inode *inode, struct kstat *stat,
struct file *file, bool *refreshed);
void fuse_flush_writepages(struct inode *inode);
void fuse_set_nowrite(struct inode *inode);
void fuse_release_nowrite(struct inode *inode);
u64 fuse_get_attr_version(struct fuse_conn *fc);
* File-system tells the kernel to invalidate cache for the given node id.
int fuse_reverse_inval_inode(struct super_block *sb, u64 nodeid,
loff_t offset, loff_t len);
* File-system tells the kernel to invalidate parent attributes and
* the dentry matching parent/name.
* If the child_nodeid is non-zero and:
* - matches the inode number for the dentry matching parent/name,
* - is not a mount point
* - is a file or oan empty directory
* then the dentry is unhashed (d_delete()).
int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid,
u64 child_nodeid, struct qstr *name);
int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
bool isdir);
* fuse_direct_io() flags
/** If set, it is WRITE; otherwise - READ */
#define FUSE_DIO_WRITE (1 << 0)
/** CUSE pass fuse_direct_io() a file which f_mapping->host is not from FUSE */
#define FUSE_DIO_CUSE (1 << 1)
ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
loff_t *ppos, int flags);
long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
unsigned int flags);
long fuse_ioctl_common(struct file *file, unsigned int cmd,
unsigned long arg, unsigned int flags);
unsigned fuse_file_poll(struct file *file, poll_table *wait);
int fuse_dev_release(struct inode *inode, struct file *file);
bool fuse_write_update_size(struct inode *inode, loff_t pos);
int fuse_flush_times(struct inode *inode, struct fuse_file *ff);
int fuse_write_inode(struct inode *inode, struct writeback_control *wbc);
int fuse_do_setattr(struct inode *inode, struct iattr *attr,
struct file *file);
void fuse_set_initialized(struct fuse_conn *fc);
#endif /* _FS_FUSE_I_H */