/**
 * fs/f2fs/dir.c
 *
 * Copyright (c) 2012 Samsung Electronics Co., Ltd.
 *             http://www.samsung.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.
 */
#include <linux/fs.h>
#include <linux/f2fs_fs.h>
#include "f2fs.h"
#include "acl.h"

static unsigned long dir_blocks(struct inode *inode)
{
	return ((unsigned long long) (i_size_read(inode) + PAGE_CACHE_SIZE - 1))
							>> PAGE_CACHE_SHIFT;
}

static unsigned int dir_buckets(unsigned int level)
{
	if (level < MAX_DIR_HASH_DEPTH / 2)
		return 1 << level;
	else
		return 1 << ((MAX_DIR_HASH_DEPTH / 2) - 1);
}

static unsigned int bucket_blocks(unsigned int level)
{
	if (level < MAX_DIR_HASH_DEPTH / 2)
		return 2;
	else
		return 4;
}

static unsigned char f2fs_filetype_table[F2FS_FT_MAX] = {
	[F2FS_FT_UNKNOWN]	= DT_UNKNOWN,
	[F2FS_FT_REG_FILE]	= DT_REG,
	[F2FS_FT_DIR]		= DT_DIR,
	[F2FS_FT_CHRDEV]	= DT_CHR,
	[F2FS_FT_BLKDEV]	= DT_BLK,
	[F2FS_FT_FIFO]		= DT_FIFO,
	[F2FS_FT_SOCK]		= DT_SOCK,
	[F2FS_FT_SYMLINK]	= DT_LNK,
};

#define S_SHIFT 12
static unsigned char f2fs_type_by_mode[S_IFMT >> S_SHIFT] = {
	[S_IFREG >> S_SHIFT]	= F2FS_FT_REG_FILE,
	[S_IFDIR >> S_SHIFT]	= F2FS_FT_DIR,
	[S_IFCHR >> S_SHIFT]	= F2FS_FT_CHRDEV,
	[S_IFBLK >> S_SHIFT]	= F2FS_FT_BLKDEV,
	[S_IFIFO >> S_SHIFT]	= F2FS_FT_FIFO,
	[S_IFSOCK >> S_SHIFT]	= F2FS_FT_SOCK,
	[S_IFLNK >> S_SHIFT]	= F2FS_FT_SYMLINK,
};

static void set_de_type(struct f2fs_dir_entry *de, struct inode *inode)
{
	mode_t mode = inode->i_mode;
	de->file_type = f2fs_type_by_mode[(mode & S_IFMT) >> S_SHIFT];
}

static unsigned long dir_block_index(unsigned int level, unsigned int idx)
{
	unsigned long i;
	unsigned long bidx = 0;

	for (i = 0; i < level; i++)
		bidx += dir_buckets(i) * bucket_blocks(i);
	bidx += idx * bucket_blocks(level);
	return bidx;
}

static bool early_match_name(const char *name, int namelen,
			f2fs_hash_t namehash, struct f2fs_dir_entry *de)
{
	if (le16_to_cpu(de->name_len) != namelen)
		return false;

	if (de->hash_code != namehash)
		return false;

	return true;
}

static struct f2fs_dir_entry *find_in_block(struct page *dentry_page,
			const char *name, int namelen, int *max_slots,
			f2fs_hash_t namehash, struct page **res_page)
{
	struct f2fs_dir_entry *de;
	unsigned long bit_pos, end_pos, next_pos;
	struct f2fs_dentry_block *dentry_blk = kmap(dentry_page);
	int slots;

	bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
					NR_DENTRY_IN_BLOCK, 0);
	while (bit_pos < NR_DENTRY_IN_BLOCK) {
		de = &dentry_blk->dentry[bit_pos];
		slots = (le16_to_cpu(de->name_len) + F2FS_NAME_LEN - 1) /
							F2FS_NAME_LEN;

		if (early_match_name(name, namelen, namehash, de)) {
			if (!memcmp(dentry_blk->filename[bit_pos],
							name, namelen)) {
				*res_page = dentry_page;
				goto found;
			}
		}
		next_pos = bit_pos + slots;
		bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
				NR_DENTRY_IN_BLOCK, next_pos);
		if (bit_pos >= NR_DENTRY_IN_BLOCK)
			end_pos = NR_DENTRY_IN_BLOCK;
		else
			end_pos = bit_pos;
		if (*max_slots < end_pos - next_pos)
			*max_slots = end_pos - next_pos;
	}

	de = NULL;
	kunmap(dentry_page);
found:
	return de;
}

static struct f2fs_dir_entry *find_in_level(struct inode *dir,
		unsigned int level, const char *name, int namelen,
			f2fs_hash_t namehash, struct page **res_page)
{
	int s = (namelen + F2FS_NAME_LEN - 1) / F2FS_NAME_LEN;
	unsigned int nbucket, nblock;
	unsigned int bidx, end_block;
	struct page *dentry_page;
	struct f2fs_dir_entry *de = NULL;
	bool room = false;
	int max_slots = 0;

	BUG_ON(level > MAX_DIR_HASH_DEPTH);

	nbucket = dir_buckets(level);
	nblock = bucket_blocks(level);

	bidx = dir_block_index(level, le32_to_cpu(namehash) % nbucket);
	end_block = bidx + nblock;

	for (; bidx < end_block; bidx++) {
		/* no need to allocate new dentry pages to all the indices */
		dentry_page = find_data_page(dir, bidx);
		if (IS_ERR(dentry_page)) {
			room = true;
			continue;
		}

		de = find_in_block(dentry_page, name, namelen,
					&max_slots, namehash, res_page);
		if (de)
			break;

		if (max_slots >= s)
			room = true;
		f2fs_put_page(dentry_page, 0);
	}

	if (!de && room && F2FS_I(dir)->chash != namehash) {
		F2FS_I(dir)->chash = namehash;
		F2FS_I(dir)->clevel = level;
	}

	return de;
}

/*
 * Find an entry in the specified directory with the wanted name.
 * It returns the page where the entry was found (as a parameter - res_page),
 * and the entry itself. Page is returned mapped and unlocked.
 * Entry is guaranteed to be valid.
 */
struct f2fs_dir_entry *f2fs_find_entry(struct inode *dir,
			struct qstr *child, struct page **res_page)
{
	const char *name = child->name;
	int namelen = child->len;
	unsigned long npages = dir_blocks(dir);
	struct f2fs_dir_entry *de = NULL;
	f2fs_hash_t name_hash;
	unsigned int max_depth;
	unsigned int level;

	if (npages == 0)
		return NULL;

	*res_page = NULL;

	name_hash = f2fs_dentry_hash(name, namelen);
	max_depth = F2FS_I(dir)->i_current_depth;

	for (level = 0; level < max_depth; level++) {
		de = find_in_level(dir, level, name,
				namelen, name_hash, res_page);
		if (de)
			break;
	}
	if (!de && F2FS_I(dir)->chash != name_hash) {
		F2FS_I(dir)->chash = name_hash;
		F2FS_I(dir)->clevel = level - 1;
	}
	return de;
}

struct f2fs_dir_entry *f2fs_parent_dir(struct inode *dir, struct page **p)
{
	struct page *page = NULL;
	struct f2fs_dir_entry *de = NULL;
	struct f2fs_dentry_block *dentry_blk = NULL;

	page = get_lock_data_page(dir, 0);
	if (IS_ERR(page))
		return NULL;

	dentry_blk = kmap(page);
	de = &dentry_blk->dentry[1];
	*p = page;
	unlock_page(page);
	return de;
}

ino_t f2fs_inode_by_name(struct inode *dir, struct qstr *qstr)
{
	ino_t res = 0;
	struct f2fs_dir_entry *de;
	struct page *page;

	de = f2fs_find_entry(dir, qstr, &page);
	if (de) {
		res = le32_to_cpu(de->ino);
		kunmap(page);
		f2fs_put_page(page, 0);
	}

	return res;
}

void f2fs_set_link(struct inode *dir, struct f2fs_dir_entry *de,
		struct page *page, struct inode *inode)
{
	struct f2fs_sb_info *sbi = F2FS_SB(dir->i_sb);

	mutex_lock_op(sbi, DENTRY_OPS);
	lock_page(page);
	wait_on_page_writeback(page);
	de->ino = cpu_to_le32(inode->i_ino);
	set_de_type(de, inode);
	kunmap(page);
	set_page_dirty(page);
	dir->i_mtime = dir->i_ctime = CURRENT_TIME;
	mark_inode_dirty(dir);
	f2fs_put_page(page, 1);
	mutex_unlock_op(sbi, DENTRY_OPS);
}

void init_dent_inode(struct dentry *dentry, struct page *ipage)
{
	struct inode *dir = dentry->d_parent->d_inode;
	struct f2fs_node *rn;

	if (IS_ERR(ipage))
		return;

	wait_on_page_writeback(ipage);

	/* copy dentry info. to this inode page */
	rn = (struct f2fs_node *)page_address(ipage);
	rn->i.i_pino = cpu_to_le32(dir->i_ino);
	rn->i.i_namelen = cpu_to_le32(dentry->d_name.len);
	memcpy(rn->i.i_name, dentry->d_name.name, dentry->d_name.len);
	set_page_dirty(ipage);
}

static int init_inode_metadata(struct inode *inode, struct dentry *dentry)
{
	struct inode *dir = dentry->d_parent->d_inode;

	if (is_inode_flag_set(F2FS_I(inode), FI_NEW_INODE)) {
		int err;
		err = new_inode_page(inode, dentry);
		if (err)
			return err;

		if (S_ISDIR(inode->i_mode)) {
			err = f2fs_make_empty(inode, dir);
			if (err) {
				remove_inode_page(inode);
				return err;
			}
		}

		err = f2fs_init_acl(inode, dir);
		if (err) {
			remove_inode_page(inode);
			return err;
		}
	} else {
		struct page *ipage;
		ipage = get_node_page(F2FS_SB(dir->i_sb), inode->i_ino);
		if (IS_ERR(ipage))
			return PTR_ERR(ipage);
		init_dent_inode(dentry, ipage);
		f2fs_put_page(ipage, 1);
	}
	if (is_inode_flag_set(F2FS_I(inode), FI_INC_LINK)) {
		inc_nlink(inode);
		f2fs_write_inode(inode, NULL);
	}
	return 0;
}

static void update_parent_metadata(struct inode *dir, struct inode *inode,
						unsigned int current_depth)
{
	bool need_dir_update = false;

	if (is_inode_flag_set(F2FS_I(inode), FI_NEW_INODE)) {
		if (S_ISDIR(inode->i_mode)) {
			inc_nlink(dir);
			need_dir_update = true;
		}
		clear_inode_flag(F2FS_I(inode), FI_NEW_INODE);
	}
	dir->i_mtime = dir->i_ctime = CURRENT_TIME;
	if (F2FS_I(dir)->i_current_depth != current_depth) {
		F2FS_I(dir)->i_current_depth = current_depth;
		need_dir_update = true;
	}

	if (need_dir_update)
		f2fs_write_inode(dir, NULL);
	else
		mark_inode_dirty(dir);

	if (is_inode_flag_set(F2FS_I(inode), FI_INC_LINK))
		clear_inode_flag(F2FS_I(inode), FI_INC_LINK);
}

static int room_for_filename(struct f2fs_dentry_block *dentry_blk, int slots)
{
	int bit_start = 0;
	int zero_start, zero_end;
next:
	zero_start = find_next_zero_bit_le(&dentry_blk->dentry_bitmap,
						NR_DENTRY_IN_BLOCK,
						bit_start);
	if (zero_start >= NR_DENTRY_IN_BLOCK)
		return NR_DENTRY_IN_BLOCK;

	zero_end = find_next_bit_le(&dentry_blk->dentry_bitmap,
						NR_DENTRY_IN_BLOCK,
						zero_start);
	if (zero_end - zero_start >= slots)
		return zero_start;

	bit_start = zero_end + 1;

	if (zero_end + 1 >= NR_DENTRY_IN_BLOCK)
		return NR_DENTRY_IN_BLOCK;
	goto next;
}

int f2fs_add_link(struct dentry *dentry, struct inode *inode)
{
	unsigned int bit_pos;
	unsigned int level;
	unsigned int current_depth;
	unsigned long bidx, block;
	f2fs_hash_t dentry_hash;
	struct f2fs_dir_entry *de;
	unsigned int nbucket, nblock;
	struct inode *dir = dentry->d_parent->d_inode;
	struct f2fs_sb_info *sbi = F2FS_SB(dir->i_sb);
	const char *name = dentry->d_name.name;
	int namelen = dentry->d_name.len;
	struct page *dentry_page = NULL;
	struct f2fs_dentry_block *dentry_blk = NULL;
	int slots = (namelen + F2FS_NAME_LEN - 1) / F2FS_NAME_LEN;
	int err = 0;
	int i;

	dentry_hash = f2fs_dentry_hash(name, dentry->d_name.len);
	level = 0;
	current_depth = F2FS_I(dir)->i_current_depth;
	if (F2FS_I(dir)->chash == dentry_hash) {
		level = F2FS_I(dir)->clevel;
		F2FS_I(dir)->chash = 0;
	}

start:
	if (current_depth == MAX_DIR_HASH_DEPTH)
		return -ENOSPC;

	/* Increase the depth, if required */
	if (level == current_depth)
		++current_depth;

	nbucket = dir_buckets(level);
	nblock = bucket_blocks(level);

	bidx = dir_block_index(level, (le32_to_cpu(dentry_hash) % nbucket));

	for (block = bidx; block <= (bidx + nblock - 1); block++) {
		mutex_lock_op(sbi, DENTRY_OPS);
		dentry_page = get_new_data_page(dir, block, true);
		if (IS_ERR(dentry_page)) {
			mutex_unlock_op(sbi, DENTRY_OPS);
			return PTR_ERR(dentry_page);
		}

		dentry_blk = kmap(dentry_page);
		bit_pos = room_for_filename(dentry_blk, slots);
		if (bit_pos < NR_DENTRY_IN_BLOCK)
			goto add_dentry;

		kunmap(dentry_page);
		f2fs_put_page(dentry_page, 1);
		mutex_unlock_op(sbi, DENTRY_OPS);
	}

	/* Move to next level to find the empty slot for new dentry */
	++level;
	goto start;
add_dentry:
	err = init_inode_metadata(inode, dentry);
	if (err)
		goto fail;

	wait_on_page_writeback(dentry_page);

	de = &dentry_blk->dentry[bit_pos];
	de->hash_code = dentry_hash;
	de->name_len = cpu_to_le16(namelen);
	memcpy(dentry_blk->filename[bit_pos], name, namelen);
	de->ino = cpu_to_le32(inode->i_ino);
	set_de_type(de, inode);
	for (i = 0; i < slots; i++)
		test_and_set_bit_le(bit_pos + i, &dentry_blk->dentry_bitmap);
	set_page_dirty(dentry_page);
	update_parent_metadata(dir, inode, current_depth);
fail:
	kunmap(dentry_page);
	f2fs_put_page(dentry_page, 1);
	mutex_unlock_op(sbi, DENTRY_OPS);
	return err;
}

/**
 * It only removes the dentry from the dentry page,corresponding name
 * entry in name page does not need to be touched during deletion.
 */
void f2fs_delete_entry(struct f2fs_dir_entry *dentry, struct page *page,
						struct inode *inode)
{
	struct	f2fs_dentry_block *dentry_blk;
	unsigned int bit_pos;
	struct address_space *mapping = page->mapping;
	struct inode *dir = mapping->host;
	struct f2fs_sb_info *sbi = F2FS_SB(dir->i_sb);
	int slots = (le16_to_cpu(dentry->name_len) + F2FS_NAME_LEN - 1) /
							F2FS_NAME_LEN;
	void *kaddr = page_address(page);
	int i;

	mutex_lock_op(sbi, DENTRY_OPS);

	lock_page(page);
	wait_on_page_writeback(page);

	dentry_blk = (struct f2fs_dentry_block *)kaddr;
	bit_pos = dentry - (struct f2fs_dir_entry *)dentry_blk->dentry;
	for (i = 0; i < slots; i++)
		test_and_clear_bit_le(bit_pos + i, &dentry_blk->dentry_bitmap);

	/* Let's check and deallocate this dentry page */
	bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
			NR_DENTRY_IN_BLOCK,
			0);
	kunmap(page); /* kunmap - pair of f2fs_find_entry */
	set_page_dirty(page);

	dir->i_ctime = dir->i_mtime = CURRENT_TIME;

	if (inode && S_ISDIR(inode->i_mode)) {
		drop_nlink(dir);
		f2fs_write_inode(dir, NULL);
	} else {
		mark_inode_dirty(dir);
	}

	if (inode) {
		inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
		drop_nlink(inode);
		if (S_ISDIR(inode->i_mode)) {
			drop_nlink(inode);
			i_size_write(inode, 0);
		}
		f2fs_write_inode(inode, NULL);
		if (inode->i_nlink == 0)
			add_orphan_inode(sbi, inode->i_ino);
	}

	if (bit_pos == NR_DENTRY_IN_BLOCK) {
		loff_t page_offset;
		truncate_hole(dir, page->index, page->index + 1);
		clear_page_dirty_for_io(page);
		ClearPageUptodate(page);
		dec_page_count(sbi, F2FS_DIRTY_DENTS);
		inode_dec_dirty_dents(dir);
		page_offset = page->index << PAGE_CACHE_SHIFT;
		f2fs_put_page(page, 1);
	} else {
		f2fs_put_page(page, 1);
	}
	mutex_unlock_op(sbi, DENTRY_OPS);
}

int f2fs_make_empty(struct inode *inode, struct inode *parent)
{
	struct page *dentry_page;
	struct f2fs_dentry_block *dentry_blk;
	struct f2fs_dir_entry *de;
	void *kaddr;

	dentry_page = get_new_data_page(inode, 0, true);
	if (IS_ERR(dentry_page))
		return PTR_ERR(dentry_page);

	kaddr = kmap_atomic(dentry_page);
	dentry_blk = (struct f2fs_dentry_block *)kaddr;

	de = &dentry_blk->dentry[0];
	de->name_len = cpu_to_le16(1);
	de->hash_code = 0;
	de->ino = cpu_to_le32(inode->i_ino);
	memcpy(dentry_blk->filename[0], ".", 1);
	set_de_type(de, inode);

	de = &dentry_blk->dentry[1];
	de->hash_code = 0;
	de->name_len = cpu_to_le16(2);
	de->ino = cpu_to_le32(parent->i_ino);
	memcpy(dentry_blk->filename[1], "..", 2);
	set_de_type(de, inode);

	test_and_set_bit_le(0, &dentry_blk->dentry_bitmap);
	test_and_set_bit_le(1, &dentry_blk->dentry_bitmap);
	kunmap_atomic(kaddr);

	set_page_dirty(dentry_page);
	f2fs_put_page(dentry_page, 1);
	return 0;
}

bool f2fs_empty_dir(struct inode *dir)
{
	unsigned long bidx;
	struct page *dentry_page;
	unsigned int bit_pos;
	struct	f2fs_dentry_block *dentry_blk;
	unsigned long nblock = dir_blocks(dir);

	for (bidx = 0; bidx < nblock; bidx++) {
		void *kaddr;
		dentry_page = get_lock_data_page(dir, bidx);
		if (IS_ERR(dentry_page)) {
			if (PTR_ERR(dentry_page) == -ENOENT)
				continue;
			else
				return false;
		}

		kaddr = kmap_atomic(dentry_page);
		dentry_blk = (struct f2fs_dentry_block *)kaddr;
		if (bidx == 0)
			bit_pos = 2;
		else
			bit_pos = 0;
		bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
						NR_DENTRY_IN_BLOCK,
						bit_pos);
		kunmap_atomic(kaddr);

		f2fs_put_page(dentry_page, 1);

		if (bit_pos < NR_DENTRY_IN_BLOCK)
			return false;
	}
	return true;
}

static int f2fs_readdir(struct file *file, void *dirent, filldir_t filldir)
{
	unsigned long pos = file->f_pos;
	struct inode *inode = file->f_dentry->d_inode;
	unsigned long npages = dir_blocks(inode);
	unsigned char *types = NULL;
	unsigned int bit_pos = 0, start_bit_pos = 0;
	int over = 0;
	struct f2fs_dentry_block *dentry_blk = NULL;
	struct f2fs_dir_entry *de = NULL;
	struct page *dentry_page = NULL;
	unsigned int n = 0;
	unsigned char d_type = DT_UNKNOWN;
	int slots;

	types = f2fs_filetype_table;
	bit_pos = (pos % NR_DENTRY_IN_BLOCK);
	n = (pos / NR_DENTRY_IN_BLOCK);

	for ( ; n < npages; n++) {
		dentry_page = get_lock_data_page(inode, n);
		if (IS_ERR(dentry_page))
			continue;

		start_bit_pos = bit_pos;
		dentry_blk = kmap(dentry_page);
		while (bit_pos < NR_DENTRY_IN_BLOCK) {
			d_type = DT_UNKNOWN;
			bit_pos = find_next_bit_le(&dentry_blk->dentry_bitmap,
							NR_DENTRY_IN_BLOCK,
							bit_pos);
			if (bit_pos >= NR_DENTRY_IN_BLOCK)
				break;

			de = &dentry_blk->dentry[bit_pos];
			if (types && de->file_type < F2FS_FT_MAX)
				d_type = types[de->file_type];

			over = filldir(dirent,
					dentry_blk->filename[bit_pos],
					le16_to_cpu(de->name_len),
					(n * NR_DENTRY_IN_BLOCK) + bit_pos,
					le32_to_cpu(de->ino), d_type);
			if (over) {
				file->f_pos += bit_pos - start_bit_pos;
				goto success;
			}
			slots = (le16_to_cpu(de->name_len) + F2FS_NAME_LEN - 1)
								/ F2FS_NAME_LEN;
			bit_pos += slots;
		}
		bit_pos = 0;
		file->f_pos = (n + 1) * NR_DENTRY_IN_BLOCK;
		kunmap(dentry_page);
		f2fs_put_page(dentry_page, 1);
		dentry_page = NULL;
	}
success:
	if (dentry_page && !IS_ERR(dentry_page)) {
		kunmap(dentry_page);
		f2fs_put_page(dentry_page, 1);
	}

	return 0;
}

const struct file_operations f2fs_dir_operations = {
	.llseek		= generic_file_llseek,
	.read		= generic_read_dir,
	.readdir	= f2fs_readdir,
	.fsync		= f2fs_sync_file,
	.unlocked_ioctl	= f2fs_ioctl,
};