Re: [PATCH 1/2] fs:regfs: add register easy filesystem

[zc <zoucao@linux.alibaba.com>]

pending ?

在 2020/10/23 上午10:57, zc 写道:
> Hi viro:
>
>   Through regfs is very sample and easy,  but i think it is a Interest 
> ,  could give  some suggestions?
>
>
> Regards,
>
> zc
>
> 在 2020/10/20 下午2:30, Zou Cao 写道:
>> register filesystem is mapping the register into file dentry, it
>> will use the io readio to get the register val. DBT file is use
>> to decript the register tree, you can use it as follow:
>>
>>     mount -t regfs -o dtb=test.dtb none /mnt
>>
>>     test.dts:
>>     / {
>>
>>     compatible = "hisilicon,hi6220-hikey", "hisilicon,hi6220";
>>     #address-cells = <0x2>;
>>     #size-cells = <0x2>;
>>     model = "HiKey Development Board";
>>
>>     gic-v3-dist{
>>         reg = <0x0 0x8000000 0x0 0x10000>;
>>         GIC_CTRL {
>>             offset = <0x0>;
>>         };
>>         GICD_TYPER {
>>             offset = <0x4>;
>>         };
>>        };
>>     };
>>
>> it will create all regiter dentry file in /mnt
>>
>> Signed-off-by: Zou Cao <zoucao@linux.alibaba.com>
>> ---
>>   fs/Kconfig             |   1 +
>>   fs/Makefile            |   1 +
>>   fs/regfs/Kconfig       |   7 +
>>   fs/regfs/Makefile      |   8 ++
>>   fs/regfs/file.c        | 107 +++++++++++++++
>>   fs/regfs/inode.c       | 354 
>> +++++++++++++++++++++++++++++++++++++++++++++++++
>>   fs/regfs/internal.h    |  32 +++++
>>   fs/regfs/regfs_inode.h |  32 +++++
>>   fs/regfs/supper.c      |  71 ++++++++++
>>   9 files changed, 613 insertions(+)
>>   create mode 100644 fs/regfs/Kconfig
>>   create mode 100644 fs/regfs/Makefile
>>   create mode 100644 fs/regfs/file.c
>>   create mode 100644 fs/regfs/inode.c
>>   create mode 100644 fs/regfs/internal.h
>>   create mode 100644 fs/regfs/regfs_inode.h
>>   create mode 100644 fs/regfs/supper.c
>>
>> diff --git a/fs/Kconfig b/fs/Kconfig
>> index a88aa3a..d95acaf 100644
>> --- a/fs/Kconfig
>> +++ b/fs/Kconfig
>> @@ -324,6 +324,7 @@ endif # NETWORK_FILESYSTEMS
>>   source "fs/nls/Kconfig"
>>   source "fs/dlm/Kconfig"
>>   source "fs/unicode/Kconfig"
>> +source "fs/regfs/Kconfig"
>>     config IO_WQ
>>       bool
>> diff --git a/fs/Makefile b/fs/Makefile
>> index 2ce5112..24f3878 100644
>> --- a/fs/Makefile
>> +++ b/fs/Makefile
>> @@ -136,3 +136,4 @@ obj-$(CONFIG_EFIVAR_FS)        += efivarfs/
>>   obj-$(CONFIG_EROFS_FS)        += erofs/
>>   obj-$(CONFIG_VBOXSF_FS)        += vboxsf/
>>   obj-$(CONFIG_ZONEFS_FS)        += zonefs/
>> +obj-$(CONFIG_REGFS_FS)        += zonefs/
>> diff --git a/fs/regfs/Kconfig b/fs/regfs/Kconfig
>> new file mode 100644
>> index 0000000..74ba85b
>> --- /dev/null
>> +++ b/fs/regfs/Kconfig
>> @@ -0,0 +1,7 @@
>> +config REGFS_FS
>> +    tristate "registers filesystem support"
>> +    depends on ARM64
>> +    help
>> +      regfs support the read and write register of device resource by
>> +      dentry filesystem, it is more easy to support bsp debug. it also
>> +      support to printk the register val when panic
>> diff --git a/fs/regfs/Makefile b/fs/regfs/Makefile
>> new file mode 100644
>> index 0000000..26d5eef
>> --- /dev/null
>> +++ b/fs/regfs/Makefile
>> @@ -0,0 +1,8 @@
>> +# SPDX-License-Identifier: GPL-2.0-only
>> +#
>> +#Makefile for the linux ramfs routines.
>> +#
>> +
>> +obj-y += regfs.o
>> +
>> +regfs-objs += inode.o file.o supper.o
>> diff --git a/fs/regfs/file.c b/fs/regfs/file.c
>> new file mode 100644
>> index 0000000..6cd9f3d
>> --- /dev/null
>> +++ b/fs/regfs/file.c
>> @@ -0,0 +1,107 @@
>> +#include <linux/fs.h>
>> +#include <linux/mm.h>
>> +#include <linux/mpage.h>
>> +#include <linux/writeback.h>
>> +#include <linux/buffer_head.h>
>> +#include <linux/kernel.h>
>> +#include <linux/mm.h>
>> +#include <linux/memcontrol.h>
>> +#include <linux/iomap.h>
>> +#include <linux/pagemap.h>
>> +#include <linux/uio.h>
>> +#include <linux/buffer_head.h>
>> +#include <linux/dax.h>
>> +#include <linux/writeback.h>
>> +#include <linux/swap.h>
>> +#include <linux/bio.h>
>> +#include <linux/sched/signal.h>
>> +#include <linux/migrate.h>
>> +
>> +#include "regfs_inode.h"
>> +#include "internal.h"
>> +
>> +ssize_t regfs_file_write_iter(struct kiocb *iocb, struct iov_iter 
>> *from)
>> +{
>> +    struct file *file = iocb->ki_filp;
>> +    struct inode *inode = file->f_mapping->host;
>> +    ssize_t ret;
>> +
>> +    inode_lock(inode);
>> +    ret = generic_write_checks(iocb, from);
>> +    if (ret > 0)
>> +        ret = __generic_file_write_iter(iocb, from);
>> +    inode_unlock(inode);
>> +
>> +    if (ret > 0)
>> +        ret = generic_write_sync(iocb, ret);
>> +    return ret;
>> +}
>> +
>> +static ssize_t regfs_file_read(struct file *file, char __user *buf, 
>> size_t len, loff_t *ppos)
>> +{
>> +    struct address_space *mapping = file->f_mapping;
>> +    struct regfs_inode_info  *info = REGFS_I(mapping->host);
>> +    char str[64];
>> +    unsigned long val;
>> +
>> +    val = readl_relaxed(info->base + info->offset);
>> +
>> +    loc_debug("name:%s base:%p val:%lx\n"
>> +            , file->f_path.dentry->d_iname
>> +            , info->base + info->offset
>> +            , val);
>> +
>> +    snprintf(str, 64, "%lx", val);
>> +
>> +    return simple_read_from_buffer(buf, len, ppos, str, strlen(str));
>> +}
>> +
>> +static ssize_t regfs_file_write(struct file *file, const char __user 
>> *buf, size_t len, loff_t *ppos)
>> +{
>> +    struct address_space *mapping = file->f_mapping;
>> +    struct regfs_inode_info  *info = REGFS_I(mapping->host);
>> +    char str[67];
>> +    unsigned long val = 0;
>> +    loff_t pos = *ppos;
>> +    size_t res;
>> +
>> +    if (pos < 0)
>> +        return -EINVAL;
>> +    if (pos >= len || len > 66)
>> +        return 0;
>> +
>> +    res = copy_from_user(str, buf, len);
>> +    if (res)
>> +        return -EFAULT;
>> +    str[len] = 0;
>> +
>> +    if (kstrtoul(str, 16, &val) < 0)
>> +        return -EINVAL;
>> +
>> +    writel_relaxed(val, info->base + info->offset);
>> +
>> +    loc_debug("name:%s base:%p val:%lx\n"
>> +            , file->f_path.dentry->d_iname
>> +            , info->base + info->offset
>> +            , val);
>> +
>> +    return len;
>> +}
>> +
>> +const struct file_operations regfs_file_operations = {
>> +    .read = regfs_file_read,
>> +    .write = regfs_file_write,
>> +};
>> +
>> +const struct inode_operations regfs_file_inode_operations = {
>> +    .setattr    = simple_setattr,
>> +    .getattr    = simple_getattr,
>> +};
>> +
>> +const struct address_space_operations regfs_aops = {
>> +    .readpage   = simple_readpage,
>> +    .write_begin    = simple_write_begin,
>> +    .write_end  = simple_write_end,
>> +    .set_page_dirty = __set_page_dirty_buffers,
>> +};
>> +
>> diff --git a/fs/regfs/inode.c b/fs/regfs/inode.c
>> new file mode 100644
>> index 0000000..1643fcd
>> --- /dev/null
>> +++ b/fs/regfs/inode.c
>> @@ -0,0 +1,354 @@
>> +/*
>> + * Resizable simple ram filesystem for Linux.
>> + *
>> + * Copyright (C) 2000 Linus Torvalds.
>> + *               2000 Transmeta Corp.
>> + *
>> + * Usage limits added by David Gibson, Linuxcare Australia.
>> + * This file is released under the GPL.
>> + */
>> +
>> +/*
>> + * NOTE! This filesystem is probably most useful
>> + * not as a real filesystem, but as an example of
>> + * how virtual filesystems can be written.
>> + *
>> + * It doesn't get much simpler than this. Consider
>> + * that this file implements the full semantics of
>> + * a POSIX-compliant read-write filesystem.
>> + *
>> + * Note in particular how the filesystem does not
>> + * need to implement any data structures of its own
>> + * to keep track of the virtual data: using the VFS
>> + * caches is sufficient.
>> + */
>> +
>> +#include <linux/fs.h>
>> +#include <linux/pagemap.h>
>> +#include <linux/highmem.h>
>> +#include <linux/time.h>
>> +#include <linux/init.h>
>> +#include <linux/string.h>
>> +#include <linux/backing-dev.h>
>> +#include <linux/sched.h>
>> +#include <linux/parser.h>
>> +#include <linux/magic.h>
>> +#include <linux/slab.h>
>> +#include <linux/kernel.h>
>> +#include <linux/of.h>
>> +#include <linux/of_fdt.h>
>> +#include <linux/libfdt.h>
>> +#include <asm/uaccess.h>
>> +#include <linux/module.h>
>> +#include "regfs_inode.h"
>> +#include "internal.h"
>> +
>> +static LIST_HEAD(regfs_head);
>> +
>> +static const struct inode_operations regfs_dir_inode_operations;
>> +int regfs_debug;
>> +module_param(regfs_debug, int, S_IRUGO);
>> +MODULE_PARM_DESC(regfs_debug, "enable regfs debug mode");
>> +
>> +struct inode *regfs_get_inode(struct super_block *sb, const struct 
>> inode *dir, umode_t mode, dev_t dev)
>> +{
>> +    struct inode *inode = new_inode(sb);
>> +
>> +    if (inode) {
>> +        inode->i_ino = get_next_ino();
>> +        inode_init_owner(inode, dir, mode);
>> +        inode->i_mapping->a_ops = &regfs_aops;
>> +        //inode->i_mapping->backing_dev_info = &regfs_backing_dev_info;
>> +        mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
>> +        mapping_set_unevictable(inode->i_mapping);
>> +        inode->i_atime = inode->i_mtime = inode->i_ctime = 
>> current_time(inode);
>> +        switch (mode & S_IFMT) {
>> +        default:
>> +            init_special_inode(inode, mode, dev);
>> +            break;
>> +        case S_IFREG:
>> +            inode->i_op = &regfs_file_inode_operations;
>> +            inode->i_fop = &regfs_file_operations;
>> +            break;
>> +        case S_IFDIR:
>> +            inode->i_op = &regfs_dir_inode_operations;
>> +            inode->i_fop = &simple_dir_operations;
>> +
>> +            /* directory inodes start off with i_nlink == 2 (for "." 
>> entry) */
>> +            inc_nlink(inode);
>> +            break;
>> +        case S_IFLNK:
>> +            inode->i_op = &page_symlink_inode_operations;
>> +            break;
>> +        }
>> +    }
>> +
>> +    return inode;
>> +}
>> +
>> +static const struct inode_operations regfs_dir_inode_operations = {
>> +    .lookup        = simple_lookup,
>> +};
>> +
>> +static struct dentry *new_dentry_create(struct super_block *sb, 
>> struct dentry *parent,
>> +         const char *name, bool is_dir, struct res_data *res)
>> +{
>> +    struct dentry *dentry;
>> +    struct inode *inode;
>> +    struct regfs_inode_info *ei;
>> +    struct regfs_fs_info *fsi = sb->s_fs_info;
>> +
>> +    dentry = d_alloc_name(parent, name);
>> +    if (!dentry)
>> +        return NULL;
>> +
>> +    inode = new_inode(sb);
>> +    if (!inode)
>> +        goto out;
>> +
>> +    ei = REGFS_I(inode);
>> +    inode->i_ino = get_next_ino();;
>> +    inode->i_mtime = inode->i_atime = inode->i_ctime = 
>> current_time(inode);
>> +    inode->i_uid =  GLOBAL_ROOT_UID;
>> +    inode->i_gid =  GLOBAL_ROOT_GID;
>> +    if (is_dir) {
>> +        inode->i_mode = S_IFDIR | S_IRUGO | S_IWUSR;
>> +        inode->i_op = &regfs_dir_inode_operations;
>> +        inode->i_fop = &simple_dir_operations;
>> +        list_add(&ei->list, &fsi->list);
>> +    } else {
>> +        inode->i_mode = S_IFREG | S_IRUGO | S_IWUSR;
>> +        inode->i_op = &regfs_file_inode_operations;
>> +        inode->i_fop = &regfs_file_operations;
>> +        inc_nlink(inode);
>> +    }
>> +    ei->base = (void *)res->base;
>> +    ei->offset = res->offset;
>> +    ei->type = res->type;
>> +
>> +    d_add(dentry, inode);
>> +
>> +    loc_debug("new dentry io base:%llx offset:%llx ei:%llx\n", 
>> (u64)ei->base, (u64)ei->offset, (u64)ei);
>> +    return dentry;
>> +out:
>> +    dput(dentry);
>> +    return NULL;
>> +}
>> +
>> +static void node_transfer_dentry(struct super_block *sb)
>> +{
>> +    struct regfs_fs_info *fsi = sb->s_fs_info;
>> +    void *blob = fsi->dtb_buf;
>> +    const char *pathp;
>> +    int node_offset, depth = -1;
>> +    struct dentry *parent = NULL;
>> +    u64 parent_base;
>> +
>> +    for (node_offset = fdt_next_node(blob, -1, &depth);
>> +        node_offset >= 0 && depth >= 0;
>> +        node_offset = fdt_next_node(blob, node_offset, &depth)) {
>> +
>> +        const struct fdt_property *prop;
>> +        struct res_data res;
>> +
>> +        pathp = fdt_get_name(blob, node_offset, NULL);
>> +        prop = (void *)fdt_getprop(blob, node_offset, "reg", NULL);
>> +
>> +        if (prop) {
>> +            unsigned long phys;
>> +
>> +            phys = fdt32_to_cpu(((const __be32 *)prop)[1]);
>> +            res.type = RES_TYPE_RANGE;
>> +            res.offset = fdt32_to_cpu(((const __be32 *)prop)[3]);
>> +            res.base = (u64)ioremap(phys, res.offset);
>> +
>> +            if (!res.base) {
>> +                parent = NULL;
>> +                parent_base = 0;
>> +                continue;
>> +            }
>> +
>> +            loc_debug("%s reg:%lx size:%lx map:%llx\n\n", pathp
>> +                 , (unsigned long) fdt32_to_cpu(((const __be32 
>> *)prop)[1])
>> +                 , (unsigned long) fdt32_to_cpu(((const __be32 
>> *)prop)[3])
>> +                 , (u64)res.base);
>> +
>> +            parent = new_dentry_create(sb, sb->s_root, (const char 
>> *)pathp, true, &res);
>> +            parent_base = res.base;
>> +
>> +        } else {
>> +            // parent dentry is create failed, igonre all child dentry
>> +            if (!parent)
>> +                continue;
>> +
>> +            prop = (void *)fdt_getprop(blob, node_offset, "offset", 
>> NULL);
>> +            if (prop) {
>> +
>> +                res.offset = fdt32_to_cpu(*(const __be32 *)prop);
>> +                res.base = parent_base;
>> +                res.type = RES_TYPE_ITEM;
>> +
>> +                new_dentry_create(sb, parent, (const char *) pathp, 
>> false, &res);
>> +                loc_debug("%s offset:%lx\n", pathp, (unsigned 
>> long)fdt32_to_cpu(*(const __be32 *)prop));
>> +            }
>> +        }
>> +    }
>> +}
>> +
>> +static int parse_options(char *options, struct super_block *sb)
>> +{
>> +    char *p;
>> +    int ret = -EINVAL;
>> +    struct regfs_fs_info *fsi;
>> +    size_t msize = INT_MAX;
>> +
>> +    fsi = sb->s_fs_info;
>> +
>> +    if (!options)
>> +        return -EINVAL;
>> +
>> +    while ((p = strsep(&options, ",")) != NULL) {
>> +        char *name, *name_val;
>> +
>> +        name = strsep(&p, "=");
>> +        if (name == NULL)
>> +            goto failed;
>> +
>> +        name_val = strsep(&p, "=");
>> +        if (name_val == NULL)
>> +            goto failed;
>> +
>> +        //get resource address
>> +        if (!strcmp(name, "dtb")) {
>> +            ret = kernel_read_file_from_path(name_val, 
>> &fsi->dtb_buf, &fsi->dtb_len, msize, READING_UNKNOWN);
>> +            if (ret) {
>> +                pr_err("load %s failed\n", name_val);
>> +                goto failed;
>> +            }
>> +        } else
>> +            goto failed;
>> +    };
>> +
>> +    return 0;
>> +
>> +failed:
>> +    return ret;
>> +}
>> +
>> +int regfs_fill_super(struct super_block *sb, void *data, int silent)
>> +{
>> +    struct regfs_fs_info *fsi;
>> +    struct inode *inode;
>> +    int err;
>> +
>> +    fsi = kzalloc(sizeof(struct regfs_fs_info), GFP_KERNEL);
>> +    if (!fsi)
>> +        return -ENOMEM;
>> +
>> +    sb->s_fs_info = fsi;
>> +    fsi->sb = sb;
>> +
>> +    err = parse_options((char *)data, sb);
>> +    if (err)
>> +        goto out;
>> +
>> +    sb->s_maxbytes        = MAX_LFS_FILESIZE;
>> +    sb->s_blocksize        = PAGE_SIZE;
>> +    sb->s_blocksize_bits    = PAGE_SHIFT;
>> +    sb->s_magic        = RAMFS_MAGIC;
>> +    sb->s_op        = &regfs_ops;
>> +    sb->s_time_gran        = 1;
>> +
>> +    inode = regfs_get_inode(sb, NULL, S_IFDIR, 0);
>> +    sb->s_root = d_make_root(inode);
>> +    if (!sb->s_root)
>> +        goto out;
>> +
>> +    INIT_LIST_HEAD(&fsi->list);
>> +    INIT_LIST_HEAD(&fsi->regfs_head);
>> +    list_add(&fsi->regfs_head, &regfs_head);
>> +
>> +    return 0;
>> +
>> +out:
>> +    if (fsi)
>> +        kfree(fsi);
>> +
>> +    return err;
>> +}
>> +
>> +struct dentry *regfs_mount(struct file_system_type *fs_type,
>> +    int flags, const char *dev_name, void *data)
>> +{
>> +    struct dentry *root_dentry;
>> +    struct super_block *sb;
>> +
>> +    root_dentry = mount_nodev(fs_type, flags, data, regfs_fill_super);
>> +
>> +    sb = root_dentry->d_sb;
>> +
>> +    if (sb->s_root) {
>> +        node_transfer_dentry(sb);
>> +    } else
>> +        return NULL;
>> +
>> +    return root_dentry;
>> +}
>> +
>> +static void regfs_kill_sb(struct super_block *sb)
>> +{
>> +    struct regfs_fs_info *fsi = sb->s_fs_info;
>> +    struct regfs_inode_info *info_res;
>> +
>> +    list_for_each_entry(info_res,  &fsi->list, list)
>> +        iounmap(info_res->base);
>> +
>> +    if (fsi) {
>> +        if (fsi->dtb_buf)
>> +            vfree(fsi->dtb_buf);
>> +        list_del(&fsi->regfs_head);
>> +        kfree(sb->s_fs_info);
>> +    }
>> +    kill_litter_super(sb);
>> +}
>> +
>> +static struct file_system_type regfs_fs_type = {
>> +    .name        = "regfs",
>> +    .mount        = regfs_mount,
>> +    .kill_sb    = regfs_kill_sb,
>> +    .fs_flags    = FS_USERNS_MOUNT,
>> +};
>> +
>> +static void init_once(void *foo)
>> +{
>> +    struct regfs_inode_info *ei = (struct regfs_inode_info *) foo;
>> +
>> +    inode_init_once(&ei->vfs_inode);
>> +}
>> +
>> +static int __init init_regfs_fs(void)
>> +{
>> +
>> +    regfs_inode_cachep = 
>> kmem_cache_create_usercopy("regfs_inode_cache",
>> +                sizeof(struct regfs_inode_info), 0,
>> +                (SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | 
>> SLAB_ACCOUNT),
>> +                0, 0, init_once);
>> +
>> +    if (!regfs_inode_cachep)
>> +        return -ENOMEM;
>> +
>> +    return  register_filesystem(&regfs_fs_type);
>> +}
>> +
>> +static void __exit exit_regfs_fs(void)
>> +{
>> +    unregister_filesystem(&regfs_fs_type);
>> +    rcu_barrier();
>> +    kmem_cache_destroy(regfs_inode_cachep);
>> +}
>> +
>> +module_init(init_regfs_fs);
>> +module_exit(exit_regfs_fs);
>> +
>> +MODULE_LICENSE("GPL");
>> +MODULE_AUTHOR("Zou Cao<zoucaox@linux.alibaba.com>");
>> diff --git a/fs/regfs/internal.h b/fs/regfs/internal.h
>> new file mode 100644
>> index 0000000..61577bb
>> --- /dev/null
>> +++ b/fs/regfs/internal.h
>> @@ -0,0 +1,32 @@
>> +#ifndef __INTERNAL_H__
>> +#define __INTERNAL_H__
>> +
>> +#define loc_debug(fmt, ...)   \
>> +    do {                       \
>> +        if (regfs_debug)   \
>> +            printk(fmt, ##__VA_ARGS__); \
>> +    } while (0)
>> +
>> +struct regfs_fs_info {
>> +    struct super_block *sb;
>> +    void   *dtb_buf;
>> +    u64      dtb_len;
>> +    u64      iomem;
>> +    u64  size;
>> +    // supper ifs list
>> +    struct list_head regfs_head;
>> +    // io map list of inode
>> +    struct list_head list;
>> +};
>> +
>> +#define RAMFS_DEFAULT_MODE    0755
>> +
>> +extern int regfs_debug;
>> +extern const struct address_space_operations regfs_aops;
>> +extern const struct inode_operations regfs_file_inode_operations;
>> +extern const struct file_operations regfs_file_operations;
>> +extern const struct super_operations regfs_ops;
>> +extern struct kmem_cache *regfs_inode_cachep;
>> +int regfs_supper_init(void);
>> +
>> +#endif
>> diff --git a/fs/regfs/regfs_inode.h b/fs/regfs/regfs_inode.h
>> new file mode 100644
>> index 0000000..0883e05
>> --- /dev/null
>> +++ b/fs/regfs/regfs_inode.h
>> @@ -0,0 +1,32 @@
>> +#ifndef __REGFS_INODE_H__
>> +#define __REGFS_INODE_H__
>> +
>> +enum res_type {
>> +    RES_TYPE_NONE = 0,
>> +    RES_TYPE_RANGE,
>> +    RES_TYPE_ITEM,
>> +};
>> +
>> +struct regfs_inode_info {
>> +    unsigned long flag;
>> +    struct inode vfs_inode;
>> +    void __iomem *base;
>> +    u64  offset;
>> +    u64  val;  //for panic save
>> +    struct list_head list;  //inode list
>> +    enum res_type type;
>> +};
>> +
>> +struct res_data {
>> +    enum res_type type;
>> +    u64  base;
>> +    u64  offset;
>> +};
>> +
>> +static inline struct regfs_inode_info *REGFS_I(struct inode *inode)
>> +{
>> +    return container_of(inode, struct regfs_inode_info, vfs_inode);
>> +}
>> +
>> +#endif
>> +
>> diff --git a/fs/regfs/supper.c b/fs/regfs/supper.c
>> new file mode 100644
>> index 0000000..35733b6
>> --- /dev/null
>> +++ b/fs/regfs/supper.c
>> @@ -0,0 +1,71 @@
>> +#include <linux/fs.h>
>> +#include <linux/pagemap.h>
>> +#include <linux/highmem.h>
>> +#include <linux/time.h>
>> +#include <linux/init.h>
>> +#include <linux/string.h>
>> +#include <linux/backing-dev.h>
>> +#include <linux/sched.h>
>> +#include <linux/parser.h>
>> +#include <linux/magic.h>
>> +#include <linux/slab.h>
>> +#include <linux/kernel.h>
>> +#include <linux/uaccess.h>
>> +#include <linux/module.h>
>> +#include <linux/iversion.h>
>> +#include "regfs_inode.h"
>> +#include "internal.h"
>> +
>> +struct kmem_cache *regfs_inode_cachep;
>> +
>> +/*
>> + * Display the mount options in /proc/mounts.
>> + */
>> +
>> +static struct inode *regfs_alloc_inode(struct super_block *sb)
>> +{
>> +    struct regfs_inode_info *ei;
>> +
>> +    ei = kmem_cache_alloc(regfs_inode_cachep, GFP_NOFS);
>> +    if (!ei)
>> +        return NULL;
>> +
>> +    inode_set_iversion(&ei->vfs_inode, 1);
>> +    ei->type = RES_TYPE_NONE;
>> +
>> +    return &ei->vfs_inode;
>> +}
>> +
>> +static void regfs_i_callback(struct rcu_head *head)
>> +{
>> +    struct inode *inode = container_of(head, struct inode, i_rcu);
>> +
>> +    kmem_cache_free(regfs_inode_cachep, REGFS_I(inode));
>> +}
>> +
>> +static void regfs_destroy_inode(struct inode *inode)
>> +{
>> +    call_rcu(&inode->i_rcu, regfs_i_callback);
>> +}
>> +
>> +static int regfs_write_inode(struct inode *inode, struct 
>> writeback_control *wbc)
>> +{
>> +    return 0;
>> +}
>> +
>> +static int regfs_drop_inode(struct inode *inode)
>> +{
>> +    return generic_drop_inode(inode);
>> +}
>> +
>> +const struct super_operations regfs_ops = {
>> +    .alloc_inode    = regfs_alloc_inode,
>> +    .destroy_inode  = regfs_destroy_inode,
>> +    .write_inode    = regfs_write_inode,
>> +    .drop_inode = regfs_drop_inode,
>> +};
>> +
>> +int regfs_supper_init(void)
>> +{
>> +    return 0;
>> +}