/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>

  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

#ifndef pr_fmt
# define pr_fmt(fmt) "fuse: " fmt
#endif

#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>
#include <linux/kref.h>
#include <linux/xattr.h>
#include <linux/pid_namespace.h>
#include <linux/refcount.h>
#include <linux/user_namespace.h>

/** Default max number of pages that can be used in a single read request */
#define FUSE_DEFAULT_MAX_PAGES_PER_REQ 32

/** Maximum of max_pages received in init_out */
#define FUSE_MAX_MAX_PAGES 256

/** Bias for fi->writectr, meaning new writepages must not be sent */
#define FUSE_NOWRITE INT_MIN

/** 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 */
#define FUSE_CTL_NUM_DENTRIES 5

/** 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;

        /* Which attributes are invalid */
        u32 inval_mask;

        /** 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;

        union {
                /* Write related fields (regular file only) */
                struct {
                        /* Files usable in writepage.  Protected by fi->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 rb_root writepages;
                };

                /* readdir cache (directory only) */
                struct {
                        /* true if fully cached */
                        bool cached;

                        /* size of cache */
                        loff_t size;

                        /* position at end of cache (position of next entry) */
                        loff_t pos;

                        /* version of the cache */
                        u64 version;

                        /* modification time of directory when cache was
                         * started */
                        struct timespec64 mtime;

                        /* iversion of directory when cache was started */
                        u64 iversion;

                        /* protects above fields */
                        spinlock_t lock;
                } rdc;
        };

        /** Miscellaneous bits describing inode state */
        unsigned long state;

        /** Lock for serializing lookup and readdir for back compatibility*/
        struct mutex mutex;

        /** Lock to protect write related fields */
        spinlock_t lock;
};

/** FUSE inode state bits */
enum {
        /** Advise readdirplus  */
        FUSE_I_ADVISE_RDPLUS,
        /** Initialized with readdirplus */
        FUSE_I_INIT_RDPLUS,
        /** An operation changing file size is in progress  */
        FUSE_I_SIZE_UNSTABLE,
};

struct fuse_conn;
struct fuse_release_args;

/** FUSE specific file data */
struct fuse_file {
        /** Fuse connection for this file */
        struct fuse_conn *fc;

        /* Argument space reserved for release */
        struct fuse_release_args *release_args;

        /** Kernel file handle guaranteed to be unique */
        u64 kh;

        /** File handle used by userspace */
        u64 fh;

        /** Node id of this file */
        u64 nodeid;

        /** Refcount */
        refcount_t count;

        /** FOPEN_* flags returned by open */
        u32 open_flags;

        /** Entry on inode's write_files list */
        struct list_head write_entry;

        /* Readdir related */
        struct {
                /*
                 * Protects below fields against (crazy) parallel readdir on
                 * same open file.  Uncontended in the normal case.
                 */
                struct mutex lock;

                /* Dir stream position */
                loff_t pos;

                /* Offset in cache */
                loff_t cache_off;

                /* Version of cache we are reading */
                u64 version;

        } readdir;

        /** 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;
};

/** One output argument of a request */
struct fuse_arg {
        unsigned size;
        void *value;
};

/** FUSE page descriptor */
struct fuse_page_desc {
        unsigned int length;
        unsigned int offset;
};

struct fuse_args {
        uint64_t nodeid;
        uint32_t opcode;
        unsigned short in_numargs;
        unsigned short out_numargs;
        bool force:1;
        bool noreply:1;
        bool nocreds:1;
        bool in_pages:1;
        bool out_pages:1;
        bool out_argvar:1;
        bool page_zeroing:1;
        bool page_replace:1;
        bool may_block:1;
        struct fuse_in_arg in_args[3];
        struct fuse_arg out_args[2];
        void (*end)(struct fuse_conn *fc, struct fuse_args *args, int error);
};

struct fuse_args_pages {
        struct fuse_args args;
        struct page **pages;
        struct fuse_page_desc *descs;
        unsigned int num_pages;
};

#define FUSE_ARGS(args) struct fuse_args args = {}

/** The request IO state (for asynchronous processing) */
struct fuse_io_priv {
        struct kref refcnt;
        int async;
        spinlock_t lock;
        unsigned reqs;
        ssize_t bytes;
        size_t size;
        __u64 offset;
        bool write;
        bool should_dirty;
        int err;
        struct kiocb *iocb;
        struct completion *done;
        bool blocking;
};

#define FUSE_IO_PRIV_SYNC(i) \
{                                       \
        .refcnt = KREF_INIT(1),         \
        .async = 0,                     \
        .iocb = i,                      \
}

/**
 * Request flags
 *
 * FR_ISREPLY:          set if the request has reply
 * FR_FORCE:            force sending of the request even if interrupted
 * FR_BACKGROUND:       request is sent in the background
 * FR_WAITING:          request is counted as "waiting"
 * FR_ABORTED:          the request was aborted
 * FR_INTERRUPTED:      the request has been interrupted
 * FR_LOCKED:           data is being copied to/from the request
 * FR_PENDING:          request is not yet in userspace
 * FR_SENT:             request is in userspace, waiting for an answer
 * FR_FINISHED:         request is finished
 * FR_PRIVATE:          request is on private list
 * FR_ASYNC:            request is asynchronous
 */
enum fuse_req_flag {
        FR_ISREPLY,
        FR_FORCE,
        FR_BACKGROUND,
        FR_WAITING,
        FR_ABORTED,
        FR_INTERRUPTED,
        FR_LOCKED,
        FR_PENDING,
        FR_SENT,
        FR_FINISHED,
        FR_PRIVATE,
        FR_ASYNC,
};

/**
 * A request to the client
 *
 * .waitq.lock protects the following fields:
 *   - FR_ABORTED
 *   - FR_LOCKED (may also be modified under fc->lock, tested under both)
 */
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;

        /* Input/output arguments */
        struct fuse_args *args;

        /** refcount */
        refcount_t count;

        /* Request flags, updated with test/set/clear_bit() */
        unsigned long flags;

        /* The request input header */
        struct {
                struct fuse_in_header h;
        } in;

        /* The request output header */
        struct {
                struct fuse_out_header h;
        } out;

        /** Used to wake up the task waiting for completion of request*/
        wait_queue_head_t waitq;

#if IS_ENABLED(CONFIG_VIRTIO_FS)
        /** virtio-fs's physically contiguous buffer for in and out args */
        void *argbuf;
#endif
};

struct fuse_iqueue;

/**
 * Input queue callbacks
 *
 * Input queue signalling is device-specific.  For example, the /dev/fuse file
 * uses fiq->waitq and fasync to wake processes that are waiting on queue
 * readiness.  These callbacks allow other device types to respond to input
 * queue activity.
 */
struct fuse_iqueue_ops {
        /**
         * Signal that a forget has been queued
         */
        void (*wake_forget_and_unlock)(struct fuse_iqueue *fiq)
                __releases(fiq->lock);

        /**
         * Signal that an INTERRUPT request has been queued
         */
        void (*wake_interrupt_and_unlock)(struct fuse_iqueue *fiq)
                __releases(fiq->lock);

        /**
         * Signal that a request has been queued
         */
        void (*wake_pending_and_unlock)(struct fuse_iqueue *fiq)
                __releases(fiq->lock);

        /**
         * Clean up when fuse_iqueue is destroyed
         */
        void (*release)(struct fuse_iqueue *fiq);
};

/** /dev/fuse input queue operations */
extern const struct fuse_iqueue_ops fuse_dev_fiq_ops;

struct fuse_iqueue {
        /** Connection established */
        unsigned connected;

        /** Lock protecting accesses to members of this structure */
        spinlock_t lock;

        /** Readers of the connection are waiting on this */
        wait_queue_head_t waitq;

        /** The next unique request id */
        u64 reqctr;

        /** The list of pending requests */
        struct list_head pending;

        /** 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;

        /** O_ASYNC requests */
        struct fasync_struct *fasync;

        /** Device-specific callbacks */
        const struct fuse_iqueue_ops *ops;

        /** Device-specific state */
        void *priv;
};

#define FUSE_PQ_HASH_BITS 8
#define FUSE_PQ_HASH_SIZE (1 << FUSE_PQ_HASH_BITS)

struct fuse_pqueue {
        /** Connection established */
        unsigned connected;

        /** Lock protecting accessess to  members of this structure */
        spinlock_t lock;

        /** Hash table of requests being processed */
        struct list_head *processing;

        /** The list of requests under I/O */
        struct list_head io;
};

/**
 * Fuse device instance
 */
struct fuse_dev {
        /** Fuse connection for this device */
        struct fuse_conn *fc;

        /** Processing queue */
        struct fuse_pqueue pq;

        /** list entry on fc->devices */
        struct list_head entry;
};

struct fuse_fs_context {
        int fd;
        unsigned int rootmode;
        kuid_t user_id;
        kgid_t group_id;
        bool is_bdev:1;
        bool fd_present:1;
        bool rootmode_present:1;
        bool user_id_present:1;
        bool group_id_present:1;
        bool default_permissions:1;
        bool allow_other:1;
        bool destroy:1;
        bool no_control:1;
        bool no_force_umount:1;
        bool no_mount_options:1;
        unsigned int max_read;
        unsigned int blksize;
        const char *subtype;

        /* fuse_dev pointer to fill in, should contain NULL on entry */
        void **fudptr;
};

/**
 * 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 */
        refcount_t count;

        /** Number of fuse_dev's */
        atomic_t dev_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 pid namespace for this mount */
        struct pid_namespace *pid_ns;

        /** The user namespace for this mount */
        struct user_namespace *user_ns;

        /** Maximum read size */
        unsigned max_read;

        /** Maximum write size */
        unsigned max_write;

        /** Maxmum number of pages that can be used in a single request */
        unsigned int max_pages;

        /** Input queue */
        struct fuse_iqueue iq;

        /** The next unique kernel file handle */
        atomic64_t 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;

        /** Protects: max_background, congestion_threshold, num_background,
         * active_background, bg_queue, blocked */
        spinlock_t bg_lock;

        /** 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;

        /** Connection established, cleared on umount, connection
            abort and device release */
        unsigned connected;

        /** Connection aborted via sysfs */
        bool aborted;

        /** 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;

        /** Return an unique read error after abort.  Only set in INIT */
        unsigned abort_err: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;

        /** write-back cache policy (default is write-through) */
        unsigned writeback_cache:1;

        /** allow parallel lookups and readdir (default is serialized) */
        unsigned parallel_dirops:1;

        /** handle fs handles killing suid/sgid/cap on write/chown/trunc */
        unsigned handle_killpriv:1;

        /** cache READLINK responses in page cache */
        unsigned cache_symlinks: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 opendir/releasedir not implemented by fs? */
        unsigned no_opendir: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;

        /** Filesystem is fully reponsible for page cache invalidation. */
        unsigned explicit_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;

        /** Is lseek not implemented by fs? */
        unsigned no_lseek:1;

        /** Does the filesystem support posix acls? */
        unsigned posix_acl:1;

        /** Check permissions based on the file mode or not? */
        unsigned default_permissions:1;

        /** Allow other than the mounter user to access the filesystem ? */
        unsigned allow_other:1;

        /** Does the filesystem support copy_file_range? */
        unsigned no_copy_file_range:1;

        /* Send DESTROY request */
        unsigned int destroy:1;

        /* Delete dentries that have gone stale */
        unsigned int delete_stale:1;

        /** Do not create entry in fusectl fs */
        unsigned int no_control:1;

        /** Do not allow MNT_FORCE umount */
        unsigned int no_force_umount:1;

        /* Do not show mount options */
        unsigned int no_mount_options:1;

        /** The number of requests waiting for completion */
        atomic_t num_waiting;

        /** Negotiated minor version */
        unsigned minor;

        /** 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;

        /** Key for lock owner ID scrambling */
        u32 scramble_key[4];

        /** Version counter for attribute changes */
        atomic64_t 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;

        /** List of device instances belonging to this connection */
        struct list_head devices;
};

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;
}

static inline int invalid_nodeid(u64 nodeid)
{
        return !nodeid || nodeid == FUSE_ROOT_ID;
}

static inline u64 fuse_get_attr_version(struct fuse_conn *fc)
{
        return atomic64_read(&fc->attr_version);
}

/** Device operations */
extern const struct file_operations fuse_dev_operations;

extern const struct dentry_operations fuse_dentry_operations;
extern const struct dentry_operations fuse_root_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, const 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);

struct fuse_forget_link *fuse_dequeue_forget(struct fuse_iqueue *fiq,
                                             unsigned int max,
                                             unsigned int *countp);

/*
 * Initialize READ or READDIR request
 */
struct fuse_io_args {
        union {
                struct {
                        struct fuse_read_in in;
                        u64 attr_ver;
                } read;
                struct {
                        struct fuse_write_in in;
                        struct fuse_write_out out;
                } write;
        };
        struct fuse_args_pages ap;
        struct fuse_io_priv *io;
        struct fuse_file *ff;
};

void fuse_read_args_fill(struct fuse_io_args *ia, 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);
void fuse_file_free(struct fuse_file *ff);
void fuse_finish_open(struct inode *inode, struct file *file);

void fuse_sync_release(struct fuse_inode *fi, struct fuse_file *ff, int flags);

/**
 * Send RELEASE or RELEASEDIR request
 */
void fuse_release_common(struct file *file, bool isdir);

/**
 * Send FSYNC or FSYNCDIR request
 */
int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
                      int datasync, int opcode);

/**
 * 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);

/**
 * Simple request sending that does request allocation and freeing
 */
ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args);
int fuse_simple_background(struct fuse_conn *fc, struct fuse_args *args,
                           gfp_t gfp_flags);

/**
 * End a finished request
 */
void fuse_request_end(struct fuse_conn *fc, struct fuse_req *req);

/* Abort all requests */
void fuse_abort_conn(struct fuse_conn *fc);
void fuse_wait_aborted(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);

u64 entry_attr_timeout(struct fuse_entry_out *o);
void fuse_change_entry_timeout(struct dentry *entry, struct fuse_entry_out *o);

/**
 * 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, struct user_namespace *user_ns,
                    const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv);

/**
 * Release reference to fuse_conn
 */
void fuse_conn_put(struct fuse_conn *fc);

struct fuse_dev *fuse_dev_alloc_install(struct fuse_conn *fc);
struct fuse_dev *fuse_dev_alloc(void);
void fuse_dev_install(struct fuse_dev *fud, struct fuse_conn *fc);
void fuse_dev_free(struct fuse_dev *fud);
void fuse_send_init(struct fuse_conn *fc);

/**
 * Fill in superblock and initialize fuse connection
 * @sb: partially-initialized superblock to fill in
 * @ctx: mount context
 */
int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx);

/**
 * Disassociate fuse connection from superblock and kill the superblock
 *
 * Calls kill_anon_super(), do not use with bdev mounts.
 */
void fuse_kill_sb_anon(struct super_block *sb);

/**
 * 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);

bool fuse_invalid_attr(struct fuse_attr *attr);

/**
 * 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);

void fuse_update_ctime(struct inode *inode);

int fuse_update_attributes(struct inode *inode, struct file *file);

void fuse_flush_writepages(struct inode *inode);

void fuse_set_nowrite(struct inode *inode);
void fuse_release_nowrite(struct inode *inode);

/**
 * 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);
__poll_t 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 dentry *dentry, struct iattr *attr,
                    struct file *file);

void fuse_set_initialized(struct fuse_conn *fc);

void fuse_unlock_inode(struct inode *inode, bool locked);
bool fuse_lock_inode(struct inode *inode);

int fuse_setxattr(struct inode *inode, const char *name, const void *value,
                  size_t size, int flags);
ssize_t fuse_getxattr(struct inode *inode, const char *name, void *value,
                      size_t size);
ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size);
int fuse_removexattr(struct inode *inode, const char *name);
extern const struct xattr_handler *fuse_xattr_handlers[];
extern const struct xattr_handler *fuse_acl_xattr_handlers[];
extern const struct xattr_handler *fuse_no_acl_xattr_handlers[];

struct posix_acl;
struct posix_acl *fuse_get_acl(struct inode *inode, int type);
int fuse_set_acl(struct inode *inode, struct posix_acl *acl, int type);


/* readdir.c */
int fuse_readdir(struct file *file, struct dir_context *ctx);

/**
 * Return the number of bytes in an arguments list
 */
unsigned int fuse_len_args(unsigned int numargs, struct fuse_arg *args);

/**
 * Get the next unique ID for a request
 */
u64 fuse_get_unique(struct fuse_iqueue *fiq);
void fuse_free_conn(struct fuse_conn *fc);

#endif /* _FS_FUSE_I_H */