/*
   * Persistent Storage - ramfs parts.
   *
   * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
   *
   *  This program is free software; you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License version 2 as
   *  published by the Free Software Foundation.
   *
   *  This program is distributed in the hope that it will be useful,
   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *  GNU General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License
   *  along with this program; if not, write to the Free Software
   *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/fsnotify.h>
  #include <linux/pagemap.h>
  #include <linux/highmem.h>
  #include <linux/time.h>
  #include <linux/init.h>

  #include <linux/list.h>

  #include <linux/string.h>
  #include <linux/mount.h>
  #include <linux/ramfs.h>

  #include <linux/parser.h>

  #include <linux/sched.h>
  #include <linux/magic.h>
  #include <linux/pstore.h>
  #include <linux/slab.h>

  #include <linux/spinlock.h>

  #include <linux/uaccess.h>
  
  #include "internal.h"
  
  #define	PSTORE_NAMELEN	64

  static DEFINE_SPINLOCK(allpstore_lock);
  static LIST_HEAD(allpstore);

  struct pstore_private {

  	struct list_head list;

  	struct pstore_info *psi;

  	enum pstore_type_id type;
  	u64	id;

  	ssize_t	size;
  	char	data[];

  };

  static int pstore_file_open(struct inode *inode, struct file *file)
  {
  	file->private_data = inode->i_private;
  	return 0;
  }
  
  static ssize_t pstore_file_read(struct file *file, char __user *userbuf,
  						size_t count, loff_t *ppos)
  {
  	struct pstore_private *ps = file->private_data;
  
  	return simple_read_from_buffer(userbuf, count, ppos, ps->data, ps->size);
  }
  
  static const struct file_operations pstore_file_operations = {
  	.open	= pstore_file_open,
  	.read	= pstore_file_read,
  	.llseek	= default_llseek,
  };

  
  /*
   * When a file is unlinked from our file system we call the
   * platform driver to erase the record from persistent store.
   */
  static int pstore_unlink(struct inode *dir, struct dentry *dentry)
  {
  	struct pstore_private *p = dentry->d_inode->i_private;

  	p->psi->erase(p->type, p->id, p->psi);

  
  	return simple_unlink(dir, dentry);
  }

  static void pstore_evict_inode(struct inode *inode)
  {

  	struct pstore_private	*p = inode->i_private;
  	unsigned long		flags;

  	end_writeback(inode);

  	if (p) {
  		spin_lock_irqsave(&allpstore_lock, flags);
  		list_del(&p->list);
  		spin_unlock_irqrestore(&allpstore_lock, flags);
  		kfree(p);
  	}

  }

  static const struct inode_operations pstore_dir_inode_operations = {
  	.lookup		= simple_lookup,
  	.unlink		= pstore_unlink,
  };

  static struct inode *pstore_get_inode(struct super_block *sb,
  					const struct inode *dir, int mode, dev_t dev)
  {
  	struct inode *inode = new_inode(sb);
  
  	if (inode) {
  		inode->i_ino = get_next_ino();
  		inode->i_uid = inode->i_gid = 0;
  		inode->i_mode = mode;
  		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  		switch (mode & S_IFMT) {
  		case S_IFREG:
  			inode->i_fop = &pstore_file_operations;
  			break;
  		case S_IFDIR:
  			inode->i_op = &pstore_dir_inode_operations;
  			inode->i_fop = &simple_dir_operations;
  			inc_nlink(inode);
  			break;
  		}
  	}
  	return inode;
  }

  enum {
  	Opt_kmsg_bytes, Opt_err
  };
  
  static const match_table_t tokens = {
  	{Opt_kmsg_bytes, "kmsg_bytes=%u"},
  	{Opt_err, NULL}
  };
  
  static void parse_options(char *options)
  {
  	char		*p;
  	substring_t	args[MAX_OPT_ARGS];
  	int		option;
  
  	if (!options)
  		return;
  
  	while ((p = strsep(&options, ",")) != NULL) {
  		int token;
  
  		if (!*p)
  			continue;
  
  		token = match_token(p, tokens, args);
  		switch (token) {
  		case Opt_kmsg_bytes:
  			if (!match_int(&args[0], &option))
  				pstore_set_kmsg_bytes(option);
  			break;
  		}
  	}
  }
  
  static int pstore_remount(struct super_block *sb, int *flags, char *data)
  {
  	parse_options(data);
  
  	return 0;
  }

  static const struct super_operations pstore_ops = {
  	.statfs		= simple_statfs,
  	.drop_inode	= generic_delete_inode,

  	.evict_inode	= pstore_evict_inode,

  	.remount_fs	= pstore_remount,

  	.show_options	= generic_show_options,
  };
  
  static struct super_block *pstore_sb;

  
  int pstore_is_mounted(void)
  {

  	return pstore_sb != NULL;

  }
  
  /*
   * Make a regular file in the root directory of our file system.
   * Load it up with "size" bytes of data from "buf".
   * Set the mtime & ctime to the date that this record was originally stored.
   */
  int pstore_mkfile(enum pstore_type_id type, char *psname, u64 id,

  		  char *data, size_t size, struct timespec time,
  		  struct pstore_info *psi)

  {
  	struct dentry		*root = pstore_sb->s_root;
  	struct dentry		*dentry;
  	struct inode		*inode;

  	int			rc = 0;

  	char			name[PSTORE_NAMELEN];

  	struct pstore_private	*private, *pos;
  	unsigned long		flags;
  
  	spin_lock_irqsave(&allpstore_lock, flags);
  	list_for_each_entry(pos, &allpstore, list) {
  		if (pos->type == type &&
  		    pos->id == id &&
  		    pos->psi == psi) {
  			rc = -EEXIST;
  			break;
  		}
  	}
  	spin_unlock_irqrestore(&allpstore_lock, flags);
  	if (rc)
  		return rc;

  
  	rc = -ENOMEM;
  	inode = pstore_get_inode(pstore_sb, root->d_inode, S_IFREG | 0444, 0);
  	if (!inode)
  		goto fail;

  	private = kmalloc(sizeof *private + size, GFP_KERNEL);

  	if (!private)
  		goto fail_alloc;

  	private->type = type;

  	private->id = id;

  	private->psi = psi;

  
  	switch (type) {
  	case PSTORE_TYPE_DMESG:
  		sprintf(name, "dmesg-%s-%lld", psname, id);
  		break;
  	case PSTORE_TYPE_MCE:
  		sprintf(name, "mce-%s-%lld", psname, id);
  		break;
  	case PSTORE_TYPE_UNKNOWN:
  		sprintf(name, "unknown-%s-%lld", psname, id);
  		break;
  	default:
  		sprintf(name, "type%d-%s-%lld", type, psname, id);
  		break;
  	}
  
  	mutex_lock(&root->d_inode->i_mutex);
  
  	rc = -ENOSPC;
  	dentry = d_alloc_name(root, name);
  	if (IS_ERR(dentry))
  		goto fail_lockedalloc;

  	memcpy(private->data, data, size);
  	inode->i_size = private->size = size;

  
  	inode->i_private = private;
  
  	if (time.tv_sec)
  		inode->i_mtime = inode->i_ctime = time;

  	d_add(dentry, inode);

  	spin_lock_irqsave(&allpstore_lock, flags);
  	list_add(&private->list, &allpstore);
  	spin_unlock_irqrestore(&allpstore_lock, flags);

  	mutex_unlock(&root->d_inode->i_mutex);

  
  	return 0;

  
  fail_lockedalloc:
  	mutex_unlock(&root->d_inode->i_mutex);
  	kfree(private);
  fail_alloc:
  	iput(inode);
  
  fail:
  	return rc;
  }
  
  int pstore_fill_super(struct super_block *sb, void *data, int silent)
  {
  	struct inode *inode = NULL;
  	struct dentry *root;
  	int err;
  
  	save_mount_options(sb, data);
  
  	pstore_sb = sb;
  
  	sb->s_maxbytes		= MAX_LFS_FILESIZE;
  	sb->s_blocksize		= PAGE_CACHE_SIZE;
  	sb->s_blocksize_bits	= PAGE_CACHE_SHIFT;
  	sb->s_magic		= PSTOREFS_MAGIC;
  	sb->s_op		= &pstore_ops;
  	sb->s_time_gran		= 1;

  	parse_options(data);

  	inode = pstore_get_inode(sb, NULL, S_IFDIR | 0755, 0);
  	if (!inode) {
  		err = -ENOMEM;
  		goto fail;
  	}
  	/* override ramfs "dir" options so we catch unlink(2) */
  	inode->i_op = &pstore_dir_inode_operations;
  
  	root = d_alloc_root(inode);
  	sb->s_root = root;
  	if (!root) {
  		err = -ENOMEM;
  		goto fail;
  	}

  	pstore_get_records(0);

  
  	return 0;
  fail:
  	iput(inode);
  	return err;
  }

  static struct dentry *pstore_mount(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data)

  {

  	return mount_single(fs_type, flags, data, pstore_fill_super);

  }
  
  static void pstore_kill_sb(struct super_block *sb)
  {
  	kill_litter_super(sb);
  	pstore_sb = NULL;

  }
  
  static struct file_system_type pstore_fs_type = {
  	.name		= "pstore",

  	.mount		= pstore_mount,

  	.kill_sb	= pstore_kill_sb,
  };
  
  static int __init init_pstore_fs(void)
  {

  	return register_filesystem(&pstore_fs_type);

  }
  module_init(init_pstore_fs)
  
  MODULE_AUTHOR("Tony Luck <tony.luck@intel.com>");
  MODULE_LICENSE("GPL");