staging: erofs: add super block operations

// SPDX-License-Identifier: GPL-2.0

/*

 * linux/drivers/staging/erofs/super.c

 *

 * Copyright (C) 2017-2018 HUAWEI, Inc.

 *             http://www.huawei.com/

 * Created by Gao Xiang <gaoxiang25@huawei.com>

 *

 * This file is subject to the terms and conditions of the GNU General Public

 * License.  See the file COPYING in the main directory of the Linux

 * distribution for more details.

 */

#include <linux/module.h>

#include <linux/buffer_head.h>

#include <linux/statfs.h>

#include <linux/parser.h>

#include "internal.h"

static struct kmem_cache *erofs_inode_cachep __read_mostly;

static void init_once(void *ptr)

{

	struct erofs_vnode *vi = ptr;

	inode_init_once(&vi->vfs_inode);

}

static int erofs_init_inode_cache(void)

{

	erofs_inode_cachep = kmem_cache_create("erofs_inode",

		sizeof(struct erofs_vnode), 0,

		SLAB_RECLAIM_ACCOUNT, init_once);

	return erofs_inode_cachep != NULL ? 0 : -ENOMEM;

}

static void erofs_exit_inode_cache(void)

{

	BUG_ON(erofs_inode_cachep == NULL);

	kmem_cache_destroy(erofs_inode_cachep);

}

static struct inode *alloc_inode(struct super_block *sb)

{

	struct erofs_vnode *vi =

		kmem_cache_alloc(erofs_inode_cachep, GFP_KERNEL);

	if (vi == NULL)

		return NULL;

	/* zero out everything except vfs_inode */

	memset(vi, 0, offsetof(struct erofs_vnode, vfs_inode));

	return &vi->vfs_inode;

}

static void i_callback(struct rcu_head *head)

{

	struct inode *inode = container_of(head, struct inode, i_rcu);

	struct erofs_vnode *vi = EROFS_V(inode);

	/* be careful RCU symlink path (see ext4_inode_info->i_data)! */

	if (is_inode_fast_symlink(inode))

		kfree(inode->i_link);

	kfree(vi->xattr_shared_xattrs);

	kmem_cache_free(erofs_inode_cachep, vi);

}

static void destroy_inode(struct inode *inode)

{

	call_rcu(&inode->i_rcu, i_callback);

}

static int superblock_read(struct super_block *sb)

{

	struct erofs_sb_info *sbi;

	struct buffer_head *bh;

	struct erofs_super_block *layout;

	unsigned blkszbits;

	int ret;

	bh = sb_bread(sb, 0);

	if (bh == NULL) {

		errln("cannot read erofs superblock");

		return -EIO;

	}

	sbi = EROFS_SB(sb);

	layout = (struct erofs_super_block *)((u8 *)bh->b_data

		 + EROFS_SUPER_OFFSET);

	ret = -EINVAL;

	if (le32_to_cpu(layout->magic) != EROFS_SUPER_MAGIC_V1) {

		errln("cannot find valid erofs superblock");

		goto out;

	}

	blkszbits = layout->blkszbits;

	/* 9(512 bytes) + LOG_SECTORS_PER_BLOCK == LOG_BLOCK_SIZE */

	if (unlikely(blkszbits != LOG_BLOCK_SIZE)) {

		errln("blksize %u isn't supported on this platform",

			1 << blkszbits);

		goto out;

	}

	sbi->blocks = le32_to_cpu(layout->blocks);

	sbi->meta_blkaddr = le32_to_cpu(layout->meta_blkaddr);

	sbi->islotbits = ffs(sizeof(struct erofs_inode_v1)) - 1;

	sbi->root_nid = le16_to_cpu(layout->root_nid);

	sbi->inos = le64_to_cpu(layout->inos);

	sbi->build_time = le64_to_cpu(layout->build_time);

	sbi->build_time_nsec = le32_to_cpu(layout->build_time_nsec);

	memcpy(&sb->s_uuid, layout->uuid, sizeof(layout->uuid));

	memcpy(sbi->volume_name, layout->volume_name,

		sizeof(layout->volume_name));

	ret = 0;

out:

	brelse(bh);

	return ret;

}

static void default_options(struct erofs_sb_info *sbi)

{

}

enum {

	Opt_err

};

static match_table_t erofs_tokens = {

	{Opt_err, NULL}

};

static int parse_options(struct super_block *sb, char *options)

{

	substring_t args[MAX_OPT_ARGS];

	char *p;

	if (!options)

		return 0;

	while ((p = strsep(&options, ",")) != NULL) {

		int token;

		if (!*p)

			continue;

		args[0].to = args[0].from = NULL;

		token = match_token(p, erofs_tokens, args);

		switch (token) {

		default:

			errln("Unrecognized mount option \"%s\" "

					"or missing value", p);

			return -EINVAL;

		}

	}

	return 0;

}

static int erofs_read_super(struct super_block *sb,

	const char *dev_name, void *data, int silent)

{

	struct inode *inode;

	struct erofs_sb_info *sbi;

	int err = -EINVAL;

	infoln("read_super, device -> %s", dev_name);

	infoln("options -> %s", (char *)data);

	if (unlikely(!sb_set_blocksize(sb, EROFS_BLKSIZ))) {

		errln("failed to set erofs blksize");

		goto err;

	}

	sbi = kzalloc(sizeof(struct erofs_sb_info), GFP_KERNEL);

	if (unlikely(sbi == NULL)) {

		err = -ENOMEM;

		goto err;

	}

	sb->s_fs_info = sbi;

	err = superblock_read(sb);

	if (err)

		goto err_sbread;

	sb->s_magic = EROFS_SUPER_MAGIC;

	sb->s_flags |= MS_RDONLY | MS_NOATIME;

	sb->s_maxbytes = MAX_LFS_FILESIZE;

	sb->s_time_gran = 1;

	sb->s_op = &erofs_sops;

	/* set erofs default mount options */

	default_options(sbi);

	err = parse_options(sb, data);

	if (err)

		goto err_parseopt;

	if (!silent)

		infoln("root inode @ nid %llu", ROOT_NID(sbi));

	/* get the root inode */

	inode = erofs_iget(sb, ROOT_NID(sbi), true);

	if (IS_ERR(inode)) {

		err = PTR_ERR(inode);

		goto err_iget;

	}

	if (!S_ISDIR(inode->i_mode)) {

		errln("rootino(nid %llu) is not a directory(i_mode %o)",

			ROOT_NID(sbi), inode->i_mode);

		err = -EINVAL;

		goto err_isdir;

	}

	sb->s_root = d_make_root(inode);

	if (sb->s_root == NULL) {

		err = -ENOMEM;

		goto err_makeroot;

	}

	/* save the device name to sbi */

	sbi->dev_name = __getname();

	if (sbi->dev_name == NULL) {

		err = -ENOMEM;

		goto err_devname;

	}

	snprintf(sbi->dev_name, PATH_MAX, "%s", dev_name);

	sbi->dev_name[PATH_MAX - 1] = '\0';

	/*

	 * We already have a positive dentry, which was instantiated

	 * by d_make_root. Just need to d_rehash it.

	 */

	d_rehash(sb->s_root);

	if (!silent)

		infoln("mounted on %s with opts: %s.", dev_name,

			(char *)data);

	return 0;

	/*

	 * please add a label for each exit point and use

	 * the following name convention, thus new features

	 * can be integrated easily without renaming labels.

	 */

err_devname:

	dput(sb->s_root);

err_makeroot:

err_isdir:

	if (sb->s_root == NULL)

		iput(inode);

err_iget:

err_parseopt:

err_sbread:

	sb->s_fs_info = NULL;

	kfree(sbi);

err:

	return err;

}

/*

 * could be triggered after deactivate_locked_super()

 * is called, thus including umount and failed to initialize.

 */

static void erofs_put_super(struct super_block *sb)

{

	struct erofs_sb_info *sbi = EROFS_SB(sb);

	/* for cases which are failed in "read_super" */

	if (sbi == NULL)

		return;

	WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);

	infoln("unmounted for %s", sbi->dev_name);

	__putname(sbi->dev_name);

	kfree(sbi);

	sb->s_fs_info = NULL;

}

struct erofs_mount_private {

	const char *dev_name;

	char *options;

};

/* support mount_bdev() with options */

static int erofs_fill_super(struct super_block *sb,

	void *_priv, int silent)

{

	struct erofs_mount_private *priv = _priv;

	return erofs_read_super(sb, priv->dev_name,

		priv->options, silent);

}

static struct dentry *erofs_mount(

	struct file_system_type *fs_type, int flags,

	const char *dev_name, void *data)

{

	struct erofs_mount_private priv = {

		.dev_name = dev_name,

		.options = data

	};

	return mount_bdev(fs_type, flags, dev_name,

		&priv, erofs_fill_super);

}

static void erofs_kill_sb(struct super_block *sb)

{

	kill_block_super(sb);

}

static struct file_system_type erofs_fs_type = {

	.owner          = THIS_MODULE,

	.name           = "erofs",

	.mount          = erofs_mount,

	.kill_sb        = erofs_kill_sb,

	.fs_flags       = FS_REQUIRES_DEV,

};

MODULE_ALIAS_FS("erofs");

static int __init erofs_module_init(void)

{

	int err;

	erofs_check_ondisk_layout_definitions();

	infoln("initializing erofs " EROFS_VERSION);

	err = erofs_init_inode_cache();

	if (err)

		goto icache_err;

	err = register_filesystem(&erofs_fs_type);

	if (err)

		goto fs_err;

	infoln("successfully to initialize erofs");

	return 0;

fs_err:

	erofs_exit_inode_cache();

icache_err:

	return err;

}

static void __exit erofs_module_exit(void)

{

	unregister_filesystem(&erofs_fs_type);

	erofs_exit_inode_cache();

	infoln("successfully finalize erofs");

}

/* get filesystem statistics */

static int erofs_statfs(struct dentry *dentry, struct kstatfs *buf)

{

	struct super_block *sb = dentry->d_sb;

	struct erofs_sb_info *sbi = EROFS_SB(sb);

	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);

	buf->f_type = sb->s_magic;

	buf->f_bsize = EROFS_BLKSIZ;

	buf->f_blocks = sbi->blocks;

	buf->f_bfree = buf->f_bavail = 0;

	buf->f_files = ULLONG_MAX;

	buf->f_ffree = ULLONG_MAX - sbi->inos;

	buf->f_namelen = EROFS_NAME_LEN;

	buf->f_fsid.val[0] = (u32)id;

	buf->f_fsid.val[1] = (u32)(id >> 32);

	return 0;

}

static int erofs_show_options(struct seq_file *seq, struct dentry *root)

{

	return 0;

}

static int erofs_remount(struct super_block *sb, int *flags, char *data)

{

	BUG_ON(!sb_rdonly(sb));

	*flags |= MS_RDONLY;

	return 0;

}

const struct super_operations erofs_sops = {

	.put_super = erofs_put_super,

	.alloc_inode = alloc_inode,

	.destroy_inode = destroy_inode,

	.statfs = erofs_statfs,

	.show_options = erofs_show_options,

	.remount_fs = erofs_remount,

};

module_init(erofs_module_init);

module_exit(erofs_module_exit);

MODULE_DESCRIPTION("Enhanced ROM File System");

MODULE_AUTHOR("Gao Xiang, Yu Chao, Miao Xie, CONSUMER BG, HUAWEI Inc.");

MODULE_LICENSE("GPL");