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Message-ID: <17f16578-170c-82ab-0054-4ff10e5c6595@linux.alibaba.com>
Date: Tue, 27 Oct 2020 17:16:15 +0800
From: zc <zoucao@...ux.alibaba.com>
To: viro@...iv.linux.org.uk
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/2] fs:regfs: add register easy filesystem
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@...ux.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 = ®fs_aops;
>> + //inode->i_mapping->backing_dev_info = ®fs_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 = ®fs_file_inode_operations;
>> + inode->i_fop = ®fs_file_operations;
>> + break;
>> + case S_IFDIR:
>> + inode->i_op = ®fs_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 = ®fs_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 = ®fs_file_inode_operations;
>> + inode->i_fop = ®fs_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 = ®fs_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, ®fs_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(®fs_fs_type);
>> +}
>> +
>> +static void __exit exit_regfs_fs(void)
>> +{
>> + unregister_filesystem(®fs_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@...ux.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;
>> +}
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