/*
 *    Hypervisor filesystem for Linux on s390.
 *
 *    Copyright IBM Corp. 2006, 2008
 *    Author(s): Michael Holzheu <holzheu@de.ibm.com>
 */

#define KMSG_COMPONENT "hypfs"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/vfs.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/time.h>
#include <linux/parser.h>
#include <linux/sysfs.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/aio.h>
#include <asm/ebcdic.h>
#include "hypfs.h"

#define HYPFS_MAGIC 0x687970    /* ASCII 'hyp' */
#define TMP_SIZE 64             /* size of temporary buffers */

static struct dentry *hypfs_create_update_file(struct dentry *dir);

struct hypfs_sb_info {
        kuid_t uid;                     /* uid used for files and dirs */
        kgid_t gid;                     /* gid used for files and dirs */
        struct dentry *update_file;     /* file to trigger update */
        time_t last_update;             /* last update time in secs since 1970 */
        struct mutex lock;              /* lock to protect update process */
};

static const struct file_operations hypfs_file_ops;
static struct file_system_type hypfs_type;
static const struct super_operations hypfs_s_ops;

/* start of list of all dentries, which have to be deleted on update */
static struct dentry *hypfs_last_dentry;

static void hypfs_update_update(struct super_block *sb)
{
        struct hypfs_sb_info *sb_info = sb->s_fs_info;
        struct inode *inode = sb_info->update_file->d_inode;

        sb_info->last_update = get_seconds();
        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
}

/* directory tree removal functions */

static void hypfs_add_dentry(struct dentry *dentry)
{
        dentry->d_fsdata = hypfs_last_dentry;
        hypfs_last_dentry = dentry;
}

static inline int hypfs_positive(struct dentry *dentry)
{
        return dentry->d_inode && !d_unhashed(dentry);
}

static void hypfs_remove(struct dentry *dentry)
{
        struct dentry *parent;

        parent = dentry->d_parent;
        mutex_lock(&parent->d_inode->i_mutex);
        if (hypfs_positive(dentry)) {
                if (S_ISDIR(dentry->d_inode->i_mode))
                        simple_rmdir(parent->d_inode, dentry);
                else
                        simple_unlink(parent->d_inode, dentry);
        }
        d_delete(dentry);
        dput(dentry);
        mutex_unlock(&parent->d_inode->i_mutex);
}

static void hypfs_delete_tree(struct dentry *root)
{
        while (hypfs_last_dentry) {
                struct dentry *next_dentry;
                next_dentry = hypfs_last_dentry->d_fsdata;
                hypfs_remove(hypfs_last_dentry);
                hypfs_last_dentry = next_dentry;
        }
}

static struct inode *hypfs_make_inode(struct super_block *sb, umode_t mode)
{
        struct inode *ret = new_inode(sb);

        if (ret) {
                struct hypfs_sb_info *hypfs_info = sb->s_fs_info;
                ret->i_ino = get_next_ino();
                ret->i_mode = mode;
                ret->i_uid = hypfs_info->uid;
                ret->i_gid = hypfs_info->gid;
                ret->i_atime = ret->i_mtime = ret->i_ctime = CURRENT_TIME;
                if (S_ISDIR(mode))
                        set_nlink(ret, 2);
        }
        return ret;
}

static void hypfs_evict_inode(struct inode *inode)
{
        clear_inode(inode);
        kfree(inode->i_private);
}

static int hypfs_open(struct inode *inode, struct file *filp)
{
        char *data = file_inode(filp)->i_private;
        struct hypfs_sb_info *fs_info;

        if (filp->f_mode & FMODE_WRITE) {
                if (!(inode->i_mode & S_IWUGO))
                        return -EACCES;
        }
        if (filp->f_mode & FMODE_READ) {
                if (!(inode->i_mode & S_IRUGO))
                        return -EACCES;
        }

        fs_info = inode->i_sb->s_fs_info;
        if(data) {
                mutex_lock(&fs_info->lock);
                filp->private_data = kstrdup(data, GFP_KERNEL);
                if (!filp->private_data) {
                        mutex_unlock(&fs_info->lock);
                        return -ENOMEM;
                }
                mutex_unlock(&fs_info->lock);
        }
        return nonseekable_open(inode, filp);
}

static ssize_t hypfs_aio_read(struct kiocb *iocb, const struct iovec *iov,
                              unsigned long nr_segs, loff_t offset)
{
        char *data;
        ssize_t ret;
        struct file *filp = iocb->ki_filp;
        /* XXX: temporary */
        char __user *buf = iov[0].iov_base;
        size_t count = iov[0].iov_len;

        if (nr_segs != 1)
                return -EINVAL;

        data = filp->private_data;
        ret = simple_read_from_buffer(buf, count, &offset, data, strlen(data));
        if (ret <= 0)
                return ret;

        iocb->ki_pos += ret;
        file_accessed(filp);

        return ret;
}
static ssize_t hypfs_aio_write(struct kiocb *iocb, const struct iovec *iov,
                              unsigned long nr_segs, loff_t offset)
{
        int rc;
        struct super_block *sb = file_inode(iocb->ki_filp)->i_sb;
        struct hypfs_sb_info *fs_info = sb->s_fs_info;
        size_t count = iov_length(iov, nr_segs);

        /*
         * Currently we only allow one update per second for two reasons:
         * 1. diag 204 is VERY expensive
         * 2. If several processes do updates in parallel and then read the
         *    hypfs data, the likelihood of collisions is reduced, if we restrict
         *    the minimum update interval. A collision occurs, if during the
         *    data gathering of one process another process triggers an update
         *    If the first process wants to ensure consistent data, it has
         *    to restart data collection in this case.
         */
        mutex_lock(&fs_info->lock);
        if (fs_info->last_update == get_seconds()) {
                rc = -EBUSY;
                goto out;
        }
        hypfs_delete_tree(sb->s_root);
        if (MACHINE_IS_VM)
                rc = hypfs_vm_create_files(sb->s_root);
        else
                rc = hypfs_diag_create_files(sb->s_root);
        if (rc) {
                pr_err("Updating the hypfs tree failed\n");
                hypfs_delete_tree(sb->s_root);
                goto out;
        }
        hypfs_update_update(sb);
        rc = count;
out:
        mutex_unlock(&fs_info->lock);
        return rc;
}

static int hypfs_release(struct inode *inode, struct file *filp)
{
        kfree(filp->private_data);
        return 0;
}

enum { opt_uid, opt_gid, opt_err };

static const match_table_t hypfs_tokens = {
        {opt_uid, "uid=%u"},
        {opt_gid, "gid=%u"},
        {opt_err, NULL}
};

static int hypfs_parse_options(char *options, struct super_block *sb)
{
        char *str;
        substring_t args[MAX_OPT_ARGS];
        kuid_t uid;
        kgid_t gid;

        if (!options)
                return 0;
        while ((str = strsep(&options, ",")) != NULL) {
                int token, option;
                struct hypfs_sb_info *hypfs_info = sb->s_fs_info;

                if (!*str)
                        continue;
                token = match_token(str, hypfs_tokens, args);
                switch (token) {
                case opt_uid:
                        if (match_int(&args[0], &option))
                                return -EINVAL;
                        uid = make_kuid(current_user_ns(), option);
                        if (!uid_valid(uid))
                                return -EINVAL;
                        hypfs_info->uid = uid;
                        break;
                case opt_gid:
                        if (match_int(&args[0], &option))
                                return -EINVAL;
                        gid = make_kgid(current_user_ns(), option);
                        if (!gid_valid(gid))
                                return -EINVAL;
                        hypfs_info->gid = gid;
                        break;
                case opt_err:
                default:
                        pr_err("%s is not a valid mount option\n", str);
                        return -EINVAL;
                }
        }
        return 0;
}

static int hypfs_show_options(struct seq_file *s, struct dentry *root)
{
        struct hypfs_sb_info *hypfs_info = root->d_sb->s_fs_info;

        seq_printf(s, ",uid=%u", from_kuid_munged(&init_user_ns, hypfs_info->uid));
        seq_printf(s, ",gid=%u", from_kgid_munged(&init_user_ns, hypfs_info->gid));
        return 0;
}

static int hypfs_fill_super(struct super_block *sb, void *data, int silent)
{
        struct inode *root_inode;
        struct dentry *root_dentry;
        int rc = 0;
        struct hypfs_sb_info *sbi;

        sbi = kzalloc(sizeof(struct hypfs_sb_info), GFP_KERNEL);
        if (!sbi)
                return -ENOMEM;
        mutex_init(&sbi->lock);
        sbi->uid = current_uid();
        sbi->gid = current_gid();
        sb->s_fs_info = sbi;
        sb->s_blocksize = PAGE_CACHE_SIZE;
        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
        sb->s_magic = HYPFS_MAGIC;
        sb->s_op = &hypfs_s_ops;
        if (hypfs_parse_options(data, sb))
                return -EINVAL;
        root_inode = hypfs_make_inode(sb, S_IFDIR | 0755);
        if (!root_inode)
                return -ENOMEM;
        root_inode->i_op = &simple_dir_inode_operations;
        root_inode->i_fop = &simple_dir_operations;
        sb->s_root = root_dentry = d_make_root(root_inode);
        if (!root_dentry)
                return -ENOMEM;
        if (MACHINE_IS_VM)
                rc = hypfs_vm_create_files(root_dentry);
        else
                rc = hypfs_diag_create_files(root_dentry);
        if (rc)
                return rc;
        sbi->update_file = hypfs_create_update_file(root_dentry);
        if (IS_ERR(sbi->update_file))
                return PTR_ERR(sbi->update_file);
        hypfs_update_update(sb);
        pr_info("Hypervisor filesystem mounted\n");
        return 0;
}

static struct dentry *hypfs_mount(struct file_system_type *fst, int flags,
                        const char *devname, void *data)
{
        return mount_single(fst, flags, data, hypfs_fill_super);
}

static void hypfs_kill_super(struct super_block *sb)
{
        struct hypfs_sb_info *sb_info = sb->s_fs_info;

        if (sb->s_root)
                hypfs_delete_tree(sb->s_root);
        if (sb_info->update_file)
                hypfs_remove(sb_info->update_file);
        kfree(sb->s_fs_info);
        sb->s_fs_info = NULL;
        kill_litter_super(sb);
}

static struct dentry *hypfs_create_file(struct dentry *parent, const char *name,
                                        char *data, umode_t mode)
{
        struct dentry *dentry;
        struct inode *inode;

        mutex_lock(&parent->d_inode->i_mutex);
        dentry = lookup_one_len(name, parent, strlen(name));
        if (IS_ERR(dentry)) {
                dentry = ERR_PTR(-ENOMEM);
                goto fail;
        }
        inode = hypfs_make_inode(parent->d_sb, mode);
        if (!inode) {
                dput(dentry);
                dentry = ERR_PTR(-ENOMEM);
                goto fail;
        }
        if (S_ISREG(mode)) {
                inode->i_fop = &hypfs_file_ops;
                if (data)
                        inode->i_size = strlen(data);
                else
                        inode->i_size = 0;
        } else if (S_ISDIR(mode)) {
                inode->i_op = &simple_dir_inode_operations;
                inode->i_fop = &simple_dir_operations;
                inc_nlink(parent->d_inode);
        } else
                BUG();
        inode->i_private = data;
        d_instantiate(dentry, inode);
        dget(dentry);
fail:
        mutex_unlock(&parent->d_inode->i_mutex);
        return dentry;
}

struct dentry *hypfs_mkdir(struct dentry *parent, const char *name)
{
        struct dentry *dentry;

        dentry = hypfs_create_file(parent, name, NULL, S_IFDIR | DIR_MODE);
        if (IS_ERR(dentry))
                return dentry;
        hypfs_add_dentry(dentry);
        return dentry;
}

static struct dentry *hypfs_create_update_file(struct dentry *dir)
{
        struct dentry *dentry;

        dentry = hypfs_create_file(dir, "update", NULL,
                                   S_IFREG | UPDATE_FILE_MODE);
        /*
         * We do not put the update file on the 'delete' list with
         * hypfs_add_dentry(), since it should not be removed when the tree
         * is updated.
         */
        return dentry;
}

struct dentry *hypfs_create_u64(struct dentry *dir,
                                const char *name, __u64 value)
{
        char *buffer;
        char tmp[TMP_SIZE];
        struct dentry *dentry;

        snprintf(tmp, TMP_SIZE, "%llu\n", (unsigned long long int)value);
        buffer = kstrdup(tmp, GFP_KERNEL);
        if (!buffer)
                return ERR_PTR(-ENOMEM);
        dentry =
            hypfs_create_file(dir, name, buffer, S_IFREG | REG_FILE_MODE);
        if (IS_ERR(dentry)) {
                kfree(buffer);
                return ERR_PTR(-ENOMEM);
        }
        hypfs_add_dentry(dentry);
        return dentry;
}

struct dentry *hypfs_create_str(struct dentry *dir,
                                const char *name, char *string)
{
        char *buffer;
        struct dentry *dentry;

        buffer = kmalloc(strlen(string) + 2, GFP_KERNEL);
        if (!buffer)
                return ERR_PTR(-ENOMEM);
        sprintf(buffer, "%s\n", string);
        dentry =
            hypfs_create_file(dir, name, buffer, S_IFREG | REG_FILE_MODE);
        if (IS_ERR(dentry)) {
                kfree(buffer);
                return ERR_PTR(-ENOMEM);
        }
        hypfs_add_dentry(dentry);
        return dentry;
}

static const struct file_operations hypfs_file_ops = {
        .open           = hypfs_open,
        .release        = hypfs_release,
        .read           = do_sync_read,
        .write          = do_sync_write,
        .aio_read       = hypfs_aio_read,
        .aio_write      = hypfs_aio_write,
        .llseek         = no_llseek,
};

static struct file_system_type hypfs_type = {
        .owner          = THIS_MODULE,
        .name           = "s390_hypfs",
        .mount          = hypfs_mount,
        .kill_sb        = hypfs_kill_super
};
MODULE_ALIAS_FS("s390_hypfs");

static const struct super_operations hypfs_s_ops = {
        .statfs         = simple_statfs,
        .evict_inode    = hypfs_evict_inode,
        .show_options   = hypfs_show_options,
};

static struct kobject *s390_kobj;

static int __init hypfs_init(void)
{
        int rc;

        rc = hypfs_dbfs_init();
        if (rc)
                return rc;
        if (hypfs_diag_init()) {
                rc = -ENODATA;
                goto fail_dbfs_exit;
        }
        if (hypfs_vm_init()) {
                rc = -ENODATA;
                goto fail_hypfs_diag_exit;
        }
        s390_kobj = kobject_create_and_add("s390", hypervisor_kobj);
        if (!s390_kobj) {
                rc = -ENOMEM;
                goto fail_hypfs_vm_exit;
        }
        rc = register_filesystem(&hypfs_type);
        if (rc)
                goto fail_filesystem;
        return 0;

fail_filesystem:
        kobject_put(s390_kobj);
fail_hypfs_vm_exit:
        hypfs_vm_exit();
fail_hypfs_diag_exit:
        hypfs_diag_exit();
fail_dbfs_exit:
        hypfs_dbfs_exit();
        pr_err("Initialization of hypfs failed with rc=%i\n", rc);
        return rc;
}

static void __exit hypfs_exit(void)
{
        hypfs_diag_exit();
        hypfs_vm_exit();
        hypfs_dbfs_exit();
        unregister_filesystem(&hypfs_type);
        kobject_put(s390_kobj);
}

module_init(hypfs_init)
module_exit(hypfs_exit)

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Michael Holzheu <holzheu@de.ibm.com>");
MODULE_DESCRIPTION("s390 Hypervisor Filesystem");