/*
   * fs/logfs/super.c
   *
   * As should be obvious for Linux kernel code, license is GPLv2
   *
   * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
   *
   * Generally contains mount/umount code and also serves as a dump area for
   * any functions that don't fit elsewhere and neither justify a file of their
   * own.
   */
  #include "logfs.h"
  #include <linux/bio.h>

  #include <linux/slab.h>

  #include <linux/blkdev.h>

  #include <linux/module.h>

  #include <linux/mtd/mtd.h>
  #include <linux/statfs.h>
  #include <linux/buffer_head.h>
  
  static DEFINE_MUTEX(emergency_mutex);
  static struct page *emergency_page;
  
  struct page *emergency_read_begin(struct address_space *mapping, pgoff_t index)
  {
  	filler_t *filler = (filler_t *)mapping->a_ops->readpage;
  	struct page *page;
  	int err;
  
  	page = read_cache_page(mapping, index, filler, NULL);
  	if (page)
  		return page;
  
  	/* No more pages available, switch to emergency page */
  	printk(KERN_INFO"Logfs: Using emergency page
  ");
  	mutex_lock(&emergency_mutex);
  	err = filler(NULL, emergency_page);
  	if (err) {
  		mutex_unlock(&emergency_mutex);
  		printk(KERN_EMERG"Logfs: Error reading emergency page
  ");
  		return ERR_PTR(err);
  	}
  	return emergency_page;
  }
  
  void emergency_read_end(struct page *page)
  {
  	if (page == emergency_page)
  		mutex_unlock(&emergency_mutex);
  	else

  		put_page(page);

  }
  
  static void dump_segfile(struct super_block *sb)
  {
  	struct logfs_super *super = logfs_super(sb);
  	struct logfs_segment_entry se;
  	u32 segno;
  
  	for (segno = 0; segno < super->s_no_segs; segno++) {
  		logfs_get_segment_entry(sb, segno, &se);
  		printk("%3x: %6x %8x", segno, be32_to_cpu(se.ec_level),
  				be32_to_cpu(se.valid));
  		if (++segno < super->s_no_segs) {
  			logfs_get_segment_entry(sb, segno, &se);
  			printk(" %6x %8x", be32_to_cpu(se.ec_level),
  					be32_to_cpu(se.valid));
  		}
  		if (++segno < super->s_no_segs) {
  			logfs_get_segment_entry(sb, segno, &se);
  			printk(" %6x %8x", be32_to_cpu(se.ec_level),
  					be32_to_cpu(se.valid));
  		}
  		if (++segno < super->s_no_segs) {
  			logfs_get_segment_entry(sb, segno, &se);
  			printk(" %6x %8x", be32_to_cpu(se.ec_level),
  					be32_to_cpu(se.valid));
  		}
  		printk("
  ");
  	}
  }
  
  /*
   * logfs_crash_dump - dump debug information to device
   *
   * The LogFS superblock only occupies part of a segment.  This function will
   * write as much debug information as it can gather into the spare space.
   */
  void logfs_crash_dump(struct super_block *sb)
  {
  	dump_segfile(sb);
  }
  
  /*

   * FIXME: There should be a reserve for root, similar to ext2.
   */
  int logfs_statfs(struct dentry *dentry, struct kstatfs *stats)
  {
  	struct super_block *sb = dentry->d_sb;
  	struct logfs_super *super = logfs_super(sb);
  
  	stats->f_type		= LOGFS_MAGIC_U32;
  	stats->f_bsize		= sb->s_blocksize;
  	stats->f_blocks		= super->s_size >> LOGFS_BLOCK_BITS >> 3;
  	stats->f_bfree		= super->s_free_bytes >> sb->s_blocksize_bits;
  	stats->f_bavail		= super->s_free_bytes >> sb->s_blocksize_bits;
  	stats->f_files		= 0;
  	stats->f_ffree		= 0;
  	stats->f_namelen	= LOGFS_MAX_NAMELEN;
  	return 0;
  }
  
  static int logfs_sb_set(struct super_block *sb, void *_super)
  {
  	struct logfs_super *super = _super;
  
  	sb->s_fs_info = super;
  	sb->s_mtd = super->s_mtd;
  	sb->s_bdev = super->s_bdev;

  #ifdef CONFIG_BLOCK

  	if (sb->s_bdev)
  		sb->s_bdi = &bdev_get_queue(sb->s_bdev)->backing_dev_info;

  #endif
  #ifdef CONFIG_MTD

  	if (sb->s_mtd)
  		sb->s_bdi = sb->s_mtd->backing_dev_info;

  #endif

  	return 0;
  }
  
  static int logfs_sb_test(struct super_block *sb, void *_super)
  {
  	struct logfs_super *super = _super;
  	struct mtd_info *mtd = super->s_mtd;
  
  	if (mtd && sb->s_mtd == mtd)
  		return 1;
  	if (super->s_bdev && sb->s_bdev == super->s_bdev)
  		return 1;
  	return 0;
  }
  
  static void set_segment_header(struct logfs_segment_header *sh, u8 type,
  		u8 level, u32 segno, u32 ec)
  {
  	sh->pad = 0;
  	sh->type = type;
  	sh->level = level;
  	sh->segno = cpu_to_be32(segno);
  	sh->ec = cpu_to_be32(ec);
  	sh->gec = cpu_to_be64(segno);
  	sh->crc = logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4);
  }
  
  static void logfs_write_ds(struct super_block *sb, struct logfs_disk_super *ds,
  		u32 segno, u32 ec)
  {
  	struct logfs_super *super = logfs_super(sb);
  	struct logfs_segment_header *sh = &ds->ds_sh;
  	int i;
  
  	memset(ds, 0, sizeof(*ds));
  	set_segment_header(sh, SEG_SUPER, 0, segno, ec);
  
  	ds->ds_ifile_levels	= super->s_ifile_levels;
  	ds->ds_iblock_levels	= super->s_iblock_levels;
  	ds->ds_data_levels	= super->s_data_levels; /* XXX: Remove */
  	ds->ds_segment_shift	= super->s_segshift;
  	ds->ds_block_shift	= sb->s_blocksize_bits;
  	ds->ds_write_shift	= super->s_writeshift;
  	ds->ds_filesystem_size	= cpu_to_be64(super->s_size);
  	ds->ds_segment_size	= cpu_to_be32(super->s_segsize);
  	ds->ds_bad_seg_reserve	= cpu_to_be32(super->s_bad_seg_reserve);
  	ds->ds_feature_incompat	= cpu_to_be64(super->s_feature_incompat);
  	ds->ds_feature_ro_compat= cpu_to_be64(super->s_feature_ro_compat);
  	ds->ds_feature_compat	= cpu_to_be64(super->s_feature_compat);
  	ds->ds_feature_flags	= cpu_to_be64(super->s_feature_flags);
  	ds->ds_root_reserve	= cpu_to_be64(super->s_root_reserve);
  	ds->ds_speed_reserve	= cpu_to_be64(super->s_speed_reserve);
  	journal_for_each(i)
  		ds->ds_journal_seg[i] = cpu_to_be32(super->s_journal_seg[i]);
  	ds->ds_magic		= cpu_to_be64(LOGFS_MAGIC);
  	ds->ds_crc = logfs_crc32(ds, sizeof(*ds),
  			LOGFS_SEGMENT_HEADERSIZE + 12);
  }
  
  static int write_one_sb(struct super_block *sb,
  		struct page *(*find_sb)(struct super_block *sb, u64 *ofs))
  {
  	struct logfs_super *super = logfs_super(sb);
  	struct logfs_disk_super *ds;
  	struct logfs_segment_entry se;
  	struct page *page;
  	u64 ofs;
  	u32 ec, segno;
  	int err;
  
  	page = find_sb(sb, &ofs);
  	if (!page)
  		return -EIO;
  	ds = page_address(page);
  	segno = seg_no(sb, ofs);
  	logfs_get_segment_entry(sb, segno, &se);
  	ec = be32_to_cpu(se.ec_level) >> 4;
  	ec++;
  	logfs_set_segment_erased(sb, segno, ec, 0);
  	logfs_write_ds(sb, ds, segno, ec);
  	err = super->s_devops->write_sb(sb, page);

  	put_page(page);

  	return err;
  }
  
  int logfs_write_sb(struct super_block *sb)
  {
  	struct logfs_super *super = logfs_super(sb);
  	int err;
  
  	/* First superblock */
  	err = write_one_sb(sb, super->s_devops->find_first_sb);
  	if (err)
  		return err;
  
  	/* Last superblock */
  	err = write_one_sb(sb, super->s_devops->find_last_sb);
  	if (err)
  		return err;
  	return 0;
  }
  
  static int ds_cmp(const void *ds0, const void *ds1)
  {
  	size_t len = sizeof(struct logfs_disk_super);
  
  	/* We know the segment headers differ, so ignore them */
  	len -= LOGFS_SEGMENT_HEADERSIZE;
  	ds0 += LOGFS_SEGMENT_HEADERSIZE;
  	ds1 += LOGFS_SEGMENT_HEADERSIZE;
  	return memcmp(ds0, ds1, len);
  }
  
  static int logfs_recover_sb(struct super_block *sb)
  {
  	struct logfs_super *super = logfs_super(sb);
  	struct logfs_disk_super _ds0, *ds0 = &_ds0;
  	struct logfs_disk_super _ds1, *ds1 = &_ds1;
  	int err, valid0, valid1;
  
  	/* read first superblock */
  	err = wbuf_read(sb, super->s_sb_ofs[0], sizeof(*ds0), ds0);
  	if (err)
  		return err;
  	/* read last superblock */
  	err = wbuf_read(sb, super->s_sb_ofs[1], sizeof(*ds1), ds1);
  	if (err)
  		return err;
  	valid0 = logfs_check_ds(ds0) == 0;
  	valid1 = logfs_check_ds(ds1) == 0;
  
  	if (!valid0 && valid1) {
  		printk(KERN_INFO"First superblock is invalid - fixing.
  ");
  		return write_one_sb(sb, super->s_devops->find_first_sb);
  	}
  	if (valid0 && !valid1) {
  		printk(KERN_INFO"Last superblock is invalid - fixing.
  ");
  		return write_one_sb(sb, super->s_devops->find_last_sb);
  	}
  	if (valid0 && valid1 && ds_cmp(ds0, ds1)) {
  		printk(KERN_INFO"Superblocks don't match - fixing.
  ");

  		return logfs_write_sb(sb);

  	}
  	/* If neither is valid now, something's wrong.  Didn't we properly
  	 * check them before?!? */
  	BUG_ON(!valid0 && !valid1);
  	return 0;
  }
  
  static int logfs_make_writeable(struct super_block *sb)
  {
  	int err;

  	err = logfs_open_segfile(sb);
  	if (err)
  		return err;

  	/* Repair any broken superblock copies */
  	err = logfs_recover_sb(sb);
  	if (err)
  		return err;
  
  	/* Check areas for trailing unaccounted data */
  	err = logfs_check_areas(sb);
  	if (err)
  		return err;

  	/* Do one GC pass before any data gets dirtied */
  	logfs_gc_pass(sb);
  
  	/* after all initializations are done, replay the journal
  	 * for rw-mounts, if necessary */
  	err = logfs_replay_journal(sb);
  	if (err)
  		return err;
  
  	return 0;
  }

  static int logfs_get_sb_final(struct super_block *sb)

  {

  	struct logfs_super *super = logfs_super(sb);

  	struct inode *rootdir;
  	int err;
  
  	/* root dir */
  	rootdir = logfs_iget(sb, LOGFS_INO_ROOT);
  	if (IS_ERR(rootdir))
  		goto fail;

  	sb->s_root = d_make_root(rootdir);
  	if (!sb->s_root)

  		goto fail;

  	/* at that point we know that ->put_super() will be called */

  	super->s_erase_page = alloc_pages(GFP_KERNEL, 0);
  	if (!super->s_erase_page)

  		return -ENOMEM;

  	memset(page_address(super->s_erase_page), 0xFF, PAGE_SIZE);

  	/* FIXME: check for read-only mounts */
  	err = logfs_make_writeable(sb);

  	if (err) {
  		__free_page(super->s_erase_page);
  		return err;
  	}

  
  	log_super("LogFS: Finished mounting
  ");

  	return 0;

  fail:

  	iput(super->s_master_inode);
  	iput(super->s_segfile_inode);
  	iput(super->s_mapping_inode);

  	return -EIO;
  }
  
  int logfs_check_ds(struct logfs_disk_super *ds)
  {
  	struct logfs_segment_header *sh = &ds->ds_sh;
  
  	if (ds->ds_magic != cpu_to_be64(LOGFS_MAGIC))
  		return -EINVAL;
  	if (sh->crc != logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4))
  		return -EINVAL;
  	if (ds->ds_crc != logfs_crc32(ds, sizeof(*ds),
  				LOGFS_SEGMENT_HEADERSIZE + 12))
  		return -EINVAL;
  	return 0;
  }
  
  static struct page *find_super_block(struct super_block *sb)
  {
  	struct logfs_super *super = logfs_super(sb);
  	struct page *first, *last;
  
  	first = super->s_devops->find_first_sb(sb, &super->s_sb_ofs[0]);
  	if (!first || IS_ERR(first))
  		return NULL;
  	last = super->s_devops->find_last_sb(sb, &super->s_sb_ofs[1]);

  	if (!last || IS_ERR(last)) {

  		put_page(first);

  		return NULL;
  	}
  
  	if (!logfs_check_ds(page_address(first))) {

  		put_page(last);

  		return first;
  	}
  
  	/* First one didn't work, try the second superblock */
  	if (!logfs_check_ds(page_address(last))) {

  		put_page(first);

  		return last;
  	}
  
  	/* Neither worked, sorry folks */

  	put_page(first);
  	put_page(last);

  	return NULL;
  }
  
  static int __logfs_read_sb(struct super_block *sb)
  {
  	struct logfs_super *super = logfs_super(sb);
  	struct page *page;
  	struct logfs_disk_super *ds;
  	int i;
  
  	page = find_super_block(sb);
  	if (!page)

  		return -EINVAL;

  
  	ds = page_address(page);
  	super->s_size = be64_to_cpu(ds->ds_filesystem_size);
  	super->s_root_reserve = be64_to_cpu(ds->ds_root_reserve);
  	super->s_speed_reserve = be64_to_cpu(ds->ds_speed_reserve);
  	super->s_bad_seg_reserve = be32_to_cpu(ds->ds_bad_seg_reserve);
  	super->s_segsize = 1 << ds->ds_segment_shift;
  	super->s_segmask = (1 << ds->ds_segment_shift) - 1;
  	super->s_segshift = ds->ds_segment_shift;
  	sb->s_blocksize = 1 << ds->ds_block_shift;
  	sb->s_blocksize_bits = ds->ds_block_shift;
  	super->s_writesize = 1 << ds->ds_write_shift;
  	super->s_writeshift = ds->ds_write_shift;
  	super->s_no_segs = super->s_size >> super->s_segshift;
  	super->s_no_blocks = super->s_segsize >> sb->s_blocksize_bits;
  	super->s_feature_incompat = be64_to_cpu(ds->ds_feature_incompat);
  	super->s_feature_ro_compat = be64_to_cpu(ds->ds_feature_ro_compat);
  	super->s_feature_compat = be64_to_cpu(ds->ds_feature_compat);
  	super->s_feature_flags = be64_to_cpu(ds->ds_feature_flags);
  
  	journal_for_each(i)
  		super->s_journal_seg[i] = be32_to_cpu(ds->ds_journal_seg[i]);
  
  	super->s_ifile_levels = ds->ds_ifile_levels;
  	super->s_iblock_levels = ds->ds_iblock_levels;
  	super->s_data_levels = ds->ds_data_levels;
  	super->s_total_levels = super->s_ifile_levels + super->s_iblock_levels
  		+ super->s_data_levels;

  	put_page(page);

  	return 0;
  }

  static int logfs_read_sb(struct super_block *sb, int read_only)

  {
  	struct logfs_super *super = logfs_super(sb);
  	int ret;
  
  	super->s_btree_pool = mempool_create(32, btree_alloc, btree_free, NULL);
  	if (!super->s_btree_pool)
  		return -ENOMEM;
  
  	btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool);
  	btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool);

  	btree_init_mempool32(&super->s_shadow_tree.segment_map,
  			super->s_btree_pool);

  
  	ret = logfs_init_mapping(sb);
  	if (ret)
  		return ret;
  
  	ret = __logfs_read_sb(sb);
  	if (ret)
  		return ret;

  	if (super->s_feature_incompat & ~LOGFS_FEATURES_INCOMPAT)
  		return -EIO;
  	if ((super->s_feature_ro_compat & ~LOGFS_FEATURES_RO_COMPAT) &&
  			!read_only)
  		return -EIO;

  	ret = logfs_init_rw(sb);
  	if (ret)
  		return ret;
  
  	ret = logfs_init_areas(sb);
  	if (ret)
  		return ret;
  
  	ret = logfs_init_gc(sb);
  	if (ret)
  		return ret;
  
  	ret = logfs_init_journal(sb);
  	if (ret)
  		return ret;
  
  	return 0;
  }
  
  static void logfs_kill_sb(struct super_block *sb)
  {
  	struct logfs_super *super = logfs_super(sb);
  
  	log_super("LogFS: Start unmounting
  ");
  	/* Alias entries slow down mount, so evict as many as possible */
  	sync_filesystem(sb);

  	logfs_write_anchor(sb);

  	free_areas(sb);

  
  	/*
  	 * From this point on alias entries are simply dropped - and any
  	 * writes to the object store are considered bugs.
  	 */

  	log_super("LogFS: Now in shutdown
  ");
  	generic_shutdown_super(sb);

  	super->s_flags |= LOGFS_SB_FLAG_SHUTDOWN;

  
  	BUG_ON(super->s_dirty_used_bytes || super->s_dirty_free_bytes);
  
  	logfs_cleanup_gc(sb);
  	logfs_cleanup_journal(sb);
  	logfs_cleanup_areas(sb);
  	logfs_cleanup_rw(sb);

  	if (super->s_erase_page)
  		__free_page(super->s_erase_page);

  	super->s_devops->put_device(super);

  	logfs_mempool_destroy(super->s_btree_pool);
  	logfs_mempool_destroy(super->s_alias_pool);

  	kfree(super);
  	log_super("LogFS: Finished unmounting
  ");
  }

  static struct dentry *logfs_get_sb_device(struct logfs_super *super,
  		struct file_system_type *type, int flags)

  {

  	struct super_block *sb;
  	int err = -ENOMEM;
  	static int mount_count;
  
  	log_super("LogFS: Start mount %x
  ", mount_count++);

  	err = -EINVAL;

  	sb = sget(type, logfs_sb_test, logfs_sb_set, flags | MS_NOATIME, super);

  	if (IS_ERR(sb)) {
  		super->s_devops->put_device(super);
  		kfree(super);
  		return ERR_CAST(sb);
  	}

  
  	if (sb->s_root) {
  		/* Device is already in use */

  		super->s_devops->put_device(super);
  		kfree(super);
  		return dget(sb->s_root);

  	}

  	/*
  	 * sb->s_maxbytes is limited to 8TB.  On 32bit systems, the page cache
  	 * only covers 16TB and the upper 8TB are used for indirect blocks.
  	 * On 64bit system we could bump up the limit, but that would make
  	 * the filesystem incompatible with 32bit systems.
  	 */
  	sb->s_maxbytes	= (1ull << 43) - 1;

  	sb->s_max_links = LOGFS_LINK_MAX;

  	sb->s_op	= &logfs_super_operations;

  	err = logfs_read_sb(sb, sb->s_flags & MS_RDONLY);

  	if (err)
  		goto err1;
  
  	sb->s_flags |= MS_ACTIVE;

  	err = logfs_get_sb_final(sb);
  	if (err) {

  		deactivate_locked_super(sb);

  		return ERR_PTR(err);
  	}
  	return dget(sb->s_root);

  
  err1:

  	/* no ->s_root, no ->put_super() */
  	iput(super->s_master_inode);
  	iput(super->s_segfile_inode);
  	iput(super->s_mapping_inode);

  	deactivate_locked_super(sb);

  	return ERR_PTR(err);

  }

  static struct dentry *logfs_mount(struct file_system_type *type, int flags,
  		const char *devname, void *data)

  {
  	ulong mtdnr;

  	struct logfs_super *super;

  	int err;

  
  	super = kzalloc(sizeof(*super), GFP_KERNEL);
  	if (!super)

  		return ERR_PTR(-ENOMEM);

  	mutex_init(&super->s_dirop_mutex);
  	mutex_init(&super->s_object_alias_mutex);
  	INIT_LIST_HEAD(&super->s_freeing_list);

  	if (!devname)

  		err = logfs_get_sb_bdev(super, type, devname);
  	else if (strncmp(devname, "mtd", 3))
  		err = logfs_get_sb_bdev(super, type, devname);
  	else {

  		char *garbage;
  		mtdnr = simple_strtoul(devname+3, &garbage, 0);

  		if (*garbage)
  			err = -EINVAL;
  		else
  			err = logfs_get_sb_mtd(super, mtdnr);
  	}
  
  	if (err) {
  		kfree(super);

  		return ERR_PTR(err);

  	}

  	return logfs_get_sb_device(super, type, flags);

  }
  
  static struct file_system_type logfs_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "logfs",

  	.mount		= logfs_mount,

  	.kill_sb	= logfs_kill_sb,
  	.fs_flags	= FS_REQUIRES_DEV,
  
  };

  MODULE_ALIAS_FS("logfs");

  
  static int __init logfs_init(void)
  {
  	int ret;
  
  	emergency_page = alloc_pages(GFP_KERNEL, 0);
  	if (!emergency_page)
  		return -ENOMEM;
  
  	ret = logfs_compr_init();
  	if (ret)
  		goto out1;
  
  	ret = logfs_init_inode_cache();
  	if (ret)
  		goto out2;

  	ret = register_filesystem(&logfs_fs_type);
  	if (!ret)
  		return 0;
  	logfs_destroy_inode_cache();

  out2:
  	logfs_compr_exit();
  out1:
  	__free_pages(emergency_page, 0);
  	return ret;
  }
  
  static void __exit logfs_exit(void)
  {
  	unregister_filesystem(&logfs_fs_type);
  	logfs_destroy_inode_cache();
  	logfs_compr_exit();
  	__free_pages(emergency_page, 0);
  }
  
  module_init(logfs_init);
  module_exit(logfs_exit);
  
  MODULE_LICENSE("GPL v2");
  MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
  MODULE_DESCRIPTION("scalable flash filesystem");