/*
  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

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

/** Maximum length of a filename, not including terminating null */

/* maximum, small enough for FUSE_MIN_READ_BUFFER*/
#define FUSE_NAME_LOW_MAX 1024
/* maximum, but needs a request buffer > FUSE_MIN_READ_BUFFER */
#define FUSE_NAME_MAX (PATH_MAX - 1)

/** Number of dentries for each connection in the control filesystem */
#define FUSE_CTL_NUM_DENTRIES 5

/* Frequency (in seconds) of request timeout checks, if opted into */
#define FUSE_TIMEOUT_TIMER_FREQ 15

/** Frequency (in jiffies) of request timeout checks, if opted into */
extern const unsigned long fuse_timeout_timer_freq;

/*
 * Dentries invalidation workqueue period, in seconds.  The value of this
 * parameter shall be >= FUSE_DENTRY_INVAL_FREQ_MIN seconds, or 0 (zero), in
 * which case no workqueue will be created.
 */
extern unsigned inval_wq __read_mostly;

/** Maximum of max_pages received in init_out */
extern unsigned int fuse_max_pages_limit;
/*
 * Default timeout (in seconds) for the server to reply to a request
 * before the connection is aborted, if no timeout was specified on mount.
 */
extern unsigned int fuse_default_req_timeout;
/*
 * Max timeout (in seconds) for the server to reply to a request before
 * the connection is aborted.
 */
extern unsigned int fuse_max_req_timeout;

/** 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 int max_user_bgreq;
extern unsigned int max_user_congthresh;

/* One forget request */
struct fuse_forget_link {
        struct fuse_forget_one forget_one;
        struct fuse_forget_link *next;
};

/* Submount lookup tracking */
struct fuse_submount_lookup {
        /** Refcount */
        refcount_t count;

        /** Unique ID, which identifies the inode between userspace
         * and kernel */
        u64 nodeid;

        /** The request used for sending the FORGET message */
        struct fuse_forget_link *forget;
};

/** Container for data related to mapping to backing file */
struct fuse_backing {
        struct file *file;
        struct cred *cred;

        /** refcount */
        refcount_t count;
        struct rcu_head rcu;
};

/** 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;

        /* Cache birthtime */
        struct timespec64 i_btime;

        /** 64 bit inode number */
        u64 orig_ino;

        /** Version of last attribute change */
        u64 attr_version;

        union {
                /* read/write io cache (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;

                        /** Number of files/maps using page cache */
                        int iocachectr;

                        /* Waitq for writepage completion */
                        wait_queue_head_t page_waitq;

                        /* waitq for direct-io completion */
                        wait_queue_head_t direct_io_waitq;
                };

                /* 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;

#ifdef CONFIG_FUSE_DAX
        /*
         * Dax specific inode data
         */
        struct fuse_inode_dax *dax;
#endif
        /** Submount specific lookup tracking */
        struct fuse_submount_lookup *submount_lookup;
#ifdef CONFIG_FUSE_PASSTHROUGH
        /** Reference to backing file in passthrough mode */
        struct fuse_backing *fb;
#endif

        /*
         * The underlying inode->i_blkbits value will not be modified,
         * so preserve the blocksize specified by the server.
         */
        u8 cached_i_blkbits;
};

/** 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,
        /* Bad inode */
        FUSE_I_BAD,
        /* Has btime */
        FUSE_I_BTIME,
        /* Wants or already has page cache IO */
        FUSE_I_CACHE_IO_MODE,
        /*
         * Client has exclusive access to the inode, either because fs is local
         * or the fuse server has an exclusive "lease" on distributed fs
         */
        FUSE_I_EXCLUSIVE,
};

struct fuse_conn;
struct fuse_mount;
union fuse_file_args;

/** FUSE specific file data */
struct fuse_file {
        /** Fuse connection for this file */
        struct fuse_mount *fm;

        /* Argument space reserved for open/release */
        union fuse_file_args *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 {
                /* 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;

        /** Does file hold a fi->iocachectr refcount? */
        enum { IOM_NONE, IOM_CACHED, IOM_UNCACHED } iomode;

#ifdef CONFIG_FUSE_PASSTHROUGH
        /** Reference to backing file in passthrough mode */
        struct file *passthrough;
        const struct cred *cred;
#endif

        /** 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 folio descriptor */
struct fuse_folio_desc {
        unsigned int length;
        unsigned int offset;
};

struct fuse_args {
        uint64_t nodeid;
        uint32_t opcode;
        uint8_t in_numargs;
        uint8_t out_numargs;
        uint8_t ext_idx;
        bool force:1;
        bool noreply:1;
        bool nocreds:1;
        bool in_pages:1;
        bool out_pages:1;
        bool user_pages:1;
        bool out_argvar:1;
        bool page_zeroing:1;
        bool page_replace:1;
        bool may_block:1;
        bool is_ext:1;
        bool is_pinned:1;
        bool invalidate_vmap:1;
        struct fuse_in_arg in_args[4];
        struct fuse_arg out_args[2];
        void (*end)(struct fuse_mount *fm, struct fuse_args *args, int error);
        /* Used for kvec iter backed by vmalloc address */
        void *vmap_base;
};

struct fuse_args_pages {
        struct fuse_args args;
        struct folio **folios;
        struct fuse_folio_desc *descs;
        unsigned int num_folios;
};

struct fuse_release_args {
        struct fuse_args args;
        struct fuse_release_in inarg;
        struct inode *inode;
};

union fuse_file_args {
        /* Used during open() */
        struct fuse_open_out open_outarg;
        /* Used during release() */
        struct fuse_release_args release_args;
};

#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
 * FR_URING:            request is handled through fuse-io-uring
 */
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,
        FR_URING,
};

/**
 * 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

        /** fuse_mount this request belongs to */
        struct fuse_mount *fm;

#ifdef CONFIG_FUSE_IO_URING
        void *ring_entry;
        void *ring_queue;
#endif
        /** When (in jiffies) the request was created */
        unsigned long create_time;
};

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 {
        /**
         * Send one forget
         */
        void (*send_forget)(struct fuse_iqueue *fiq, struct fuse_forget_link *link);

        /**
         * Send interrupt for request
         */
        void (*send_interrupt)(struct fuse_iqueue *fiq, struct fuse_req *req);

        /**
         * Send one request
         */
        void (*send_req)(struct fuse_iqueue *fiq, struct fuse_req *req);

        /**
         * 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;
};

enum fuse_dax_mode {
        FUSE_DAX_INODE_DEFAULT, /* default */
        FUSE_DAX_ALWAYS,        /* "-o dax=always" */
        FUSE_DAX_NEVER,         /* "-o dax=never" */
        FUSE_DAX_INODE_USER,    /* "-o dax=inode" */
};

static inline bool fuse_is_inode_dax_mode(enum fuse_dax_mode mode)
{
        return mode == FUSE_DAX_INODE_DEFAULT || mode == FUSE_DAX_INODE_USER;
}

struct fuse_fs_context {
        int fd;
        struct file *file;
        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 legacy_opts_show:1;
        enum fuse_dax_mode dax_mode;
        unsigned int max_read;
        unsigned int blksize;
        const char *subtype;

        /* DAX device, may be NULL */
        struct dax_device *dax_dev;

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

struct fuse_sync_bucket {
        /* count is a possible scalability bottleneck */
        atomic_t count;
        wait_queue_head_t waitq;
        struct rcu_head rcu;
};

/**
 * A Fuse connection.
 *
 * This structure is created, when the root filesystem is mounted, and
 * is destroyed, when the client device is closed and the last
 * fuse_mount is destroyed.
 */
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;

        /** Current epoch for up-to-date dentries */
        atomic_t epoch;

        struct work_struct epoch_work;

        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;

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

        /** Constrain ->max_pages to this value during feature negotiation */
        unsigned int max_pages_limit;

        /** 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 readahead 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;

        /* show legacy mount options */
        unsigned int legacy_opts_show:1;

        /*
         * fs kills suid/sgid/cap on write/chown/trunc. suid is killed on
         * write/trunc only if caller did not have CAP_FSETID.  sgid is killed
         * on write/truncate only if caller did not have CAP_FSETID as well as
         * file has group execute permission.
         */
        unsigned handle_killpriv_v2:1;

        /*
         * 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;

        /** Does file server support extended setxattr */
        unsigned setxattr_ext: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 responsible 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;

        /** Does the filesystem support copy_file_range_64? */
        unsigned no_copy_file_range_64:1;

        /* 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;

        /* Auto-mount submounts announced by the server */
        unsigned int auto_submounts:1;

        /* Propagate syncfs() to server */
        unsigned int sync_fs:1;

        /* Initialize security xattrs when creating a new inode */
        unsigned int init_security:1;

        /* Add supplementary group info when creating a new inode */
        unsigned int create_supp_group:1;

        /* Does the filesystem support per inode DAX? */
        unsigned int inode_dax:1;

        /* Is tmpfile not implemented by fs? */
        unsigned int no_tmpfile:1;

        /* Relax restrictions to allow shared mmap in FOPEN_DIRECT_IO mode */
        unsigned int direct_io_allow_mmap:1;

        /* Is statx not implemented by fs? */
        unsigned int no_statx:1;

        /** Passthrough support for read/write IO */
        unsigned int passthrough:1;

        /* Use pages instead of pointer for kernel I/O */
        unsigned int use_pages_for_kvec_io:1;

        /* Is link not implemented by fs? */
        unsigned int no_link:1;

        /* Is synchronous FUSE_INIT allowed? */
        unsigned int sync_init:1;

        /* Use io_uring for communication */
        unsigned int io_uring;

        /** Maximum stack depth for passthrough backing files */
        int max_stack_depth;

        /** 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 the root super block */
        dev_t dev;

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

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

        /** Version counter for evict inode */
        atomic64_t evict_ctr;

        /* maximum file name length */
        u32 name_max;

        /** Called on final put */
        void (*release)(struct fuse_conn *);

        /**
         * Read/write semaphore to hold when accessing the sb of any
         * fuse_mount belonging to this connection
         */
        struct rw_semaphore killsb;

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

#ifdef CONFIG_FUSE_DAX
        /* Dax mode */
        enum fuse_dax_mode dax_mode;

        /* Dax specific conn data, non-NULL if DAX is enabled */
        struct fuse_conn_dax *dax;
#endif

        /** List of filesystems using this connection */
        struct list_head mounts;

        /* New writepages go into this bucket */
        struct fuse_sync_bucket __rcu *curr_bucket;

#ifdef CONFIG_FUSE_PASSTHROUGH
        /** IDR for backing files ids */
        struct idr backing_files_map;
#endif

#ifdef CONFIG_FUSE_IO_URING
        /**  uring connection information*/
        struct fuse_ring *ring;
#endif

        /** Only used if the connection opts into request timeouts */
        struct {
                /* Worker for checking if any requests have timed out */
                struct delayed_work work;

                /* Request timeout (in jiffies). 0 = no timeout */
                unsigned int req_timeout;
        } timeout;
};

/*
 * Represents a mounted filesystem, potentially a submount.
 *
 * This object allows sharing a fuse_conn between separate mounts to
 * allow submounts with dedicated superblocks and thus separate device
 * IDs.
 */
struct fuse_mount {
        /* Underlying (potentially shared) connection to the FUSE server */
        struct fuse_conn *fc;

        /*
         * Super block for this connection (fc->killsb must be held when
         * accessing this).
         */
        struct super_block *sb;

        /* Entry on fc->mounts */
        struct list_head fc_entry;
        struct rcu_head rcu;
};

/*
 * Empty header for FUSE opcodes without specific header needs.
 * Used as a placeholder in args->in_args[0] for consistency
 * across all FUSE operations, simplifying request handling.
 */
struct fuse_zero_header {};

static inline void fuse_set_zero_arg0(struct fuse_args *args)
{
        args->in_args[0].size = sizeof(struct fuse_zero_header);
        args->in_args[0].value = NULL;
}

static inline struct fuse_mount *get_fuse_mount_super(struct super_block *sb)
{
        return sb->s_fs_info;
}

static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)
{
        return get_fuse_mount_super(sb)->fc;
}

static inline struct fuse_mount *get_fuse_mount(struct inode *inode)
{
        return get_fuse_mount_super(inode->i_sb);
}

static inline struct fuse_conn *get_fuse_conn(struct inode *inode)
{
        return get_fuse_mount_super(inode->i_sb)->fc;
}

static inline struct fuse_inode *get_fuse_inode(const 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);
}

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

static inline bool fuse_stale_inode(const struct inode *inode, int generation,
                                    struct fuse_attr *attr)
{
        return inode->i_generation != generation ||
                inode_wrong_type(inode, attr->mode);
}

static inline void fuse_make_bad(struct inode *inode)
{
        set_bit(FUSE_I_BAD, &get_fuse_inode(inode)->state);
}

static inline bool fuse_is_bad(struct inode *inode)
{
        return unlikely(test_bit(FUSE_I_BAD, &get_fuse_inode(inode)->state));
}

static inline bool fuse_inode_is_exclusive(const struct inode *inode)
{
        const struct fuse_inode *fi = get_fuse_inode(inode);

        return test_bit(FUSE_I_EXCLUSIVE, &fi->state);
}

static inline struct folio **fuse_folios_alloc(unsigned int nfolios, gfp_t flags,
                                               struct fuse_folio_desc **desc)
{
        struct folio **folios;

        folios = kzalloc(nfolios * (sizeof(struct folio *) +
                                    sizeof(struct fuse_folio_desc)), flags);
        *desc = (void *) (folios + nfolios);

        return folios;
}

static inline void fuse_folio_descs_length_init(struct fuse_folio_desc *descs,
                                                unsigned int index,
                                                unsigned int nr_folios)
{
        int i;

        for (i = index; i < index + nr_folios; i++)
                descs[i].length = PAGE_SIZE - descs[i].offset;
}

static inline void fuse_sync_bucket_dec(struct fuse_sync_bucket *bucket)
{
        /* Need RCU protection to prevent use after free after the decrement */
        rcu_read_lock();
        if (atomic_dec_and_test(&bucket->count))
                wake_up(&bucket->waitq);
        rcu_read_unlock();
}

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

extern const struct dentry_operations fuse_dentry_operations;

/**
 * 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,
                        u64 evict_ctr);

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);

/*
 * 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;
                        bool folio_locked;
                } 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);


struct fuse_file *fuse_file_alloc(struct fuse_mount *fm, bool release);
void fuse_file_free(struct fuse_file *ff);
int fuse_finish_open(struct inode *inode, struct file *file);

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

/**
 * 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,
                            struct fuse_statx *sx,
                            u64 attr_valid, u64 attr_version);

void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
                                   struct fuse_statx *sx,
                                   u64 attr_valid, u32 cache_mask,
                                   u64 evict_ctr);

u32 fuse_get_cache_mask(struct inode *inode);

/**
 * 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 mnt_idmap *idmap,
                              struct fuse_mount *fm,
                              struct fuse_args *args);

static inline ssize_t fuse_simple_request(struct fuse_mount *fm, struct fuse_args *args)
{
        return __fuse_simple_request(&invalid_mnt_idmap, fm, args);
}

static inline ssize_t fuse_simple_idmap_request(struct mnt_idmap *idmap,
                                                struct fuse_mount *fm,
                                                struct fuse_args *args)
{
        return __fuse_simple_request(idmap, fm, args);
}

int fuse_simple_background(struct fuse_mount *fm, struct fuse_args *args,
                           gfp_t gfp_flags);

/**
 * Assign a unique id to a fuse request
 */
void fuse_request_assign_unique(struct fuse_iqueue *fiq, struct fuse_req *req);

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

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

/* Check if any requests timed out */
void fuse_check_timeout(struct work_struct *work);

void fuse_dentry_tree_init(void);
void fuse_dentry_tree_cleanup(void);

void fuse_epoch_work(struct work_struct *work);

/**
 * Invalidate inode attributes
 */

/* Attributes possibly changed on data modification */
#define FUSE_STATX_MODIFY       (STATX_MTIME | STATX_CTIME | STATX_BLOCKS)

/* Attributes possibly changed on data and/or size modification */
#define FUSE_STATX_MODSIZE      (FUSE_STATX_MODIFY | STATX_SIZE)

void fuse_invalidate_attr(struct inode *inode);
void fuse_invalidate_attr_mask(struct inode *inode, u32 mask);

void fuse_invalidate_entry_cache(struct dentry *entry);

void fuse_invalidate_atime(struct inode *inode);

u64 fuse_time_to_jiffies(u64 sec, u32 nsec);
#define ATTR_TIMEOUT(o) \
        fuse_time_to_jiffies((o)->attr_valid, (o)->attr_valid_nsec)

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 the fuse processing queue
 */
void fuse_pqueue_init(struct fuse_pqueue *fpq);

/**
 * Initialize fuse_conn
 */
void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm,
                    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);
int fuse_send_init(struct fuse_mount *fm);

/**
 * 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);

/*
 * Remove the mount from the connection
 *
 * Returns whether this was the last mount
 */
bool fuse_mount_remove(struct fuse_mount *fm);

/*
 * Setup context ops for submounts
 */
int fuse_init_fs_context_submount(struct fs_context *fsc);

/*
 * Shut down the connection (possibly sending DESTROY request).
 */
void fuse_conn_destroy(struct fuse_mount *fm);

/* Drop the connection and free the fuse mount */
void fuse_mount_destroy(struct fuse_mount *fm);

/**
 * 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?
 */
bool fuse_allow_current_process(struct fuse_conn *fc);

u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id);

void fuse_flush_time_update(struct inode *inode);
void fuse_update_ctime(struct inode *inode);

int fuse_update_attributes(struct inode *inode, struct file *file, u32 mask);

void fuse_flush_writepages(struct inode *inode);

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

/**
 * Scan all fuse_mounts belonging to fc to find the first where
 * ilookup5() returns a result.  Return that result and the
 * respective fuse_mount in *fm (unless fm is NULL).
 *
 * The caller must hold fc->killsb.
 */
struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
                           struct fuse_mount **fm);

/**
 * File-system tells the kernel to invalidate cache for the given node id.
 */
int fuse_reverse_inval_inode(struct fuse_conn *fc, 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 fuse_conn *fc, u64 parent_nodeid,
                             u64 child_nodeid, struct qstr *name, u32 flags);

/*
 * Try to prune this inode.  If neither the inode itself nor dentries associated
 * with this inode have any external reference, then the inode can be freed.
 */
void fuse_try_prune_one_inode(struct fuse_conn *fc, u64 nodeid);

int fuse_do_open(struct fuse_mount *fm, 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_attr(struct inode *inode, loff_t pos, ssize_t written);

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 mnt_idmap *idmap, 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, unsigned int extra_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 * const fuse_xattr_handlers[];

struct posix_acl;
struct posix_acl *fuse_get_inode_acl(struct inode *inode, int type, bool rcu);
struct posix_acl *fuse_get_acl(struct mnt_idmap *idmap,
                               struct dentry *dentry, int type);
int fuse_set_acl(struct mnt_idmap *, struct dentry *dentry,
                 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);

/* dax.c */

#define FUSE_IS_DAX(inode) (IS_ENABLED(CONFIG_FUSE_DAX) && IS_DAX(inode))

ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to);
ssize_t fuse_dax_write_iter(struct kiocb *iocb, struct iov_iter *from);
int fuse_dax_mmap(struct file *file, struct vm_area_struct *vma);
int fuse_dax_break_layouts(struct inode *inode, u64 dmap_start, u64 dmap_end);
int fuse_dax_conn_alloc(struct fuse_conn *fc, enum fuse_dax_mode mode,
                        struct dax_device *dax_dev);
void fuse_dax_conn_free(struct fuse_conn *fc);
bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi);
void fuse_dax_inode_init(struct inode *inode, unsigned int flags);
void fuse_dax_inode_cleanup(struct inode *inode);
void fuse_dax_dontcache(struct inode *inode, unsigned int flags);
bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment);
void fuse_dax_cancel_work(struct fuse_conn *fc);

/* ioctl.c */
long fuse_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
long fuse_file_compat_ioctl(struct file *file, unsigned int cmd,
                            unsigned long arg);
int fuse_fileattr_get(struct dentry *dentry, struct file_kattr *fa);
int fuse_fileattr_set(struct mnt_idmap *idmap,
                      struct dentry *dentry, struct file_kattr *fa);

/* iomode.c */
int fuse_file_cached_io_open(struct inode *inode, struct fuse_file *ff);
int fuse_inode_uncached_io_start(struct fuse_inode *fi,
                                 struct fuse_backing *fb);
void fuse_inode_uncached_io_end(struct fuse_inode *fi);

int fuse_file_io_open(struct file *file, struct inode *inode);
void fuse_file_io_release(struct fuse_file *ff, struct inode *inode);

/* file.c */
struct fuse_file *fuse_file_open(struct fuse_mount *fm, u64 nodeid,
                                 unsigned int open_flags, bool isdir);
void fuse_file_release(struct inode *inode, struct fuse_file *ff,
                       unsigned int open_flags, fl_owner_t id, bool isdir);

/* backing.c */
#ifdef CONFIG_FUSE_PASSTHROUGH
struct fuse_backing *fuse_backing_get(struct fuse_backing *fb);
void fuse_backing_put(struct fuse_backing *fb);
struct fuse_backing *fuse_backing_lookup(struct fuse_conn *fc, int backing_id);
#else

static inline struct fuse_backing *fuse_backing_get(struct fuse_backing *fb)
{
        return NULL;
}

static inline void fuse_backing_put(struct fuse_backing *fb)
{
}
static inline struct fuse_backing *fuse_backing_lookup(struct fuse_conn *fc,
                                                       int backing_id)
{
        return NULL;
}
#endif

void fuse_backing_files_init(struct fuse_conn *fc);
void fuse_backing_files_free(struct fuse_conn *fc);
int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map);
int fuse_backing_close(struct fuse_conn *fc, int backing_id);

/* passthrough.c */
static inline struct fuse_backing *fuse_inode_backing(struct fuse_inode *fi)
{
#ifdef CONFIG_FUSE_PASSTHROUGH
        return READ_ONCE(fi->fb);
#else
        return NULL;
#endif
}

static inline struct fuse_backing *fuse_inode_backing_set(struct fuse_inode *fi,
                                                          struct fuse_backing *fb)
{
#ifdef CONFIG_FUSE_PASSTHROUGH
        return xchg(&fi->fb, fb);
#else
        return NULL;
#endif
}

struct fuse_backing *fuse_passthrough_open(struct file *file, int backing_id);
void fuse_passthrough_release(struct fuse_file *ff, struct fuse_backing *fb);

static inline struct file *fuse_file_passthrough(struct fuse_file *ff)
{
#ifdef CONFIG_FUSE_PASSTHROUGH
        return ff->passthrough;
#else
        return NULL;
#endif
}

ssize_t fuse_passthrough_read_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t fuse_passthrough_write_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t fuse_passthrough_splice_read(struct file *in, loff_t *ppos,
                                     struct pipe_inode_info *pipe,
                                     size_t len, unsigned int flags);
ssize_t fuse_passthrough_splice_write(struct pipe_inode_info *pipe,
                                      struct file *out, loff_t *ppos,
                                      size_t len, unsigned int flags);
ssize_t fuse_passthrough_mmap(struct file *file, struct vm_area_struct *vma);

#ifdef CONFIG_SYSCTL
extern int fuse_sysctl_register(void);
extern void fuse_sysctl_unregister(void);
#else
#define fuse_sysctl_register()          (0)
#define fuse_sysctl_unregister()        do { } while (0)
#endif /* CONFIG_SYSCTL */

#endif /* _FS_FUSE_I_H */