vfs lock

struct file_lock {
    struct file_lock *fl_next;    /* singly linked list for this inode */
    struct list_head fl_link;    /* doubly linked list of all locks */
    struct list_head fl_block;    /* circular list of blocked processes */
    fl_owner_t fl_owner;
    unsigned char fl_flags;
    unsigned char fl_type;
    unsigned int fl_pid;
    struct pid *fl_nspid;
    wait_queue_head_t fl_wait;
    struct file *fl_file;
    loff_t fl_start;
    loff_t fl_end;

    struct fasync_struct *    fl_fasync; /* for lease break notifications */
    unsigned long fl_break_time;    /* for nonblocking lease breaks */

    const struct file_lock_operations *fl_ops;    /* Callbacks for filesystems */
    const struct lock_manager_operations *fl_lmops;    /* Callbacks for lockmanagers */
    union {
        struct nfs_lock_info    nfs_fl;
        struct nfs4_lock_info    nfs4_fl;
        struct {
            struct list_head link;    /* link in AFS vnode's pending_locks list */
            int state;        /* state of grant or error if -ve */
        } afs;
    } fl_u;
};

struct file_lock_operations {
    void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
    void (*fl_release_private)(struct file_lock *);
};