// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
 */

#include <linux/init.h>
#include <linux/buffer_head.h>
#include <linux/mpage.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/time.h>
#include <linux/writeback.h>
#include <linux/uio.h>
#include <linux/random.h>
#include <linux/iversion.h>

#include "exfat_raw.h"
#include "exfat_fs.h"

int __exfat_write_inode(struct inode *inode, int sync)
{
	unsigned long long on_disk_size;
	struct exfat_dentry *ep, *ep2;
	struct exfat_entry_set_cache es;
	struct super_block *sb = inode->i_sb;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	struct exfat_inode_info *ei = EXFAT_I(inode);
	bool is_dir = (ei->type == TYPE_DIR);
	struct timespec64 ts;

	if (inode->i_ino == EXFAT_ROOT_INO)
		return 0;

	/*
	 * If the inode is already unlinked, there is no need for updating it.
	 */
	if (ei->dir.dir == DIR_DELETED)
		return 0;

	if (is_dir && ei->dir.dir == sbi->root_dir && ei->entry == -1)
		return 0;

	exfat_set_volume_dirty(sb);

	/* get the directory entry of given file or directory */
	if (exfat_get_dentry_set_by_ei(&es, sb, ei))
		return -EIO;
	ep = exfat_get_dentry_cached(&es, ES_IDX_FILE);
	ep2 = exfat_get_dentry_cached(&es, ES_IDX_STREAM);

	ep->dentry.file.attr = cpu_to_le16(exfat_make_attr(inode));

	/* set FILE_INFO structure using the acquired struct exfat_dentry */
	exfat_set_entry_time(sbi, &ei->i_crtime,
			&ep->dentry.file.create_tz,
			&ep->dentry.file.create_time,
			&ep->dentry.file.create_date,
			&ep->dentry.file.create_time_cs);
	ts = inode_get_mtime(inode);
	exfat_set_entry_time(sbi, &ts,
			     &ep->dentry.file.modify_tz,
			     &ep->dentry.file.modify_time,
			     &ep->dentry.file.modify_date,
			     &ep->dentry.file.modify_time_cs);
	ts = inode_get_atime(inode);
	exfat_set_entry_time(sbi, &ts,
			     &ep->dentry.file.access_tz,
			     &ep->dentry.file.access_time,
			     &ep->dentry.file.access_date,
			     NULL);

	/* File size should be zero if there is no cluster allocated */
	on_disk_size = i_size_read(inode);

	if (ei->start_clu == EXFAT_EOF_CLUSTER)
		on_disk_size = 0;

	ep2->dentry.stream.size = cpu_to_le64(on_disk_size);
	/*
	 * mmap write does not use exfat_write_end(), valid_size may be
	 * extended to the sector-aligned length in exfat_get_block().
	 * So we need to fixup valid_size to the writren length.
	 */
	if (on_disk_size < ei->valid_size)
		ep2->dentry.stream.valid_size = ep2->dentry.stream.size;
	else
		ep2->dentry.stream.valid_size = cpu_to_le64(ei->valid_size);

	if (on_disk_size) {
		ep2->dentry.stream.flags = ei->flags;
		ep2->dentry.stream.start_clu = cpu_to_le32(ei->start_clu);
	} else {
		ep2->dentry.stream.flags = ALLOC_FAT_CHAIN;
		ep2->dentry.stream.start_clu = EXFAT_FREE_CLUSTER;
	}

	exfat_update_dir_chksum(&es);
	return exfat_put_dentry_set(&es, sync);
}

int exfat_write_inode(struct inode *inode, struct writeback_control *wbc)
{
	int ret;

	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
		return -EIO;

	mutex_lock(&EXFAT_SB(inode->i_sb)->s_lock);
	ret = __exfat_write_inode(inode, wbc->sync_mode == WB_SYNC_ALL);
	mutex_unlock(&EXFAT_SB(inode->i_sb)->s_lock);

	return ret;
}

void exfat_sync_inode(struct inode *inode)
{
	lockdep_assert_held(&EXFAT_SB(inode->i_sb)->s_lock);
	__exfat_write_inode(inode, 1);
}

/*
 * Input: inode, (logical) clu_offset, target allocation area
 * Output: errcode, cluster number
 * *clu = (~0), if it's unable to allocate a new cluster
 */
static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
		unsigned int *clu, unsigned int *count, int create)
{
	int ret;
	unsigned int last_clu;
	struct exfat_chain new_clu;
	struct super_block *sb = inode->i_sb;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	struct exfat_inode_info *ei = EXFAT_I(inode);
	unsigned int local_clu_offset = clu_offset;
	unsigned int num_to_be_allocated = 0, num_clusters;

	num_clusters = EXFAT_B_TO_CLU(exfat_ondisk_size(inode), sbi);

	if (clu_offset >= num_clusters)
		num_to_be_allocated = clu_offset - num_clusters + 1;

	if (!create && (num_to_be_allocated > 0)) {
		*clu = EXFAT_EOF_CLUSTER;
		return 0;
	}

	*clu = last_clu = ei->start_clu;

	if (*clu == EXFAT_EOF_CLUSTER) {
		*count = 0;
	} else if (ei->flags == ALLOC_NO_FAT_CHAIN) {
		last_clu += num_clusters - 1;
		if (clu_offset < num_clusters) {
			*clu += clu_offset;
			*count = min(num_clusters - clu_offset, *count);
		} else {
			*clu = EXFAT_EOF_CLUSTER;
			*count = 0;
		}
	} else {
		int err = exfat_get_cluster(inode, clu_offset,
				clu, count, &last_clu);
		if (err)
			return -EIO;
	}

	if (*clu == EXFAT_EOF_CLUSTER) {
		exfat_set_volume_dirty(sb);

		new_clu.dir = (last_clu == EXFAT_EOF_CLUSTER) ?
				EXFAT_EOF_CLUSTER : last_clu + 1;
		new_clu.size = 0;
		new_clu.flags = ei->flags;

		/* allocate a cluster */
		if (num_to_be_allocated < 1) {
			/* Broken FAT (i_sze > allocated FAT) */
			exfat_fs_error(sb, "broken FAT chain.");
			return -EIO;
		}

		ret = exfat_alloc_cluster(inode, num_to_be_allocated, &new_clu,
				inode_needs_sync(inode));
		if (ret)
			return ret;

		if (new_clu.dir == EXFAT_EOF_CLUSTER ||
		    new_clu.dir == EXFAT_FREE_CLUSTER) {
			exfat_fs_error(sb,
				"bogus cluster new allocated (last_clu : %u, new_clu : %u)",
				last_clu, new_clu.dir);
			return -EIO;
		}

		/* append to the FAT chain */
		if (last_clu == EXFAT_EOF_CLUSTER) {
			if (new_clu.flags == ALLOC_FAT_CHAIN)
				ei->flags = ALLOC_FAT_CHAIN;
			ei->start_clu = new_clu.dir;
		} else {
			if (new_clu.flags != ei->flags) {
				/* no-fat-chain bit is disabled,
				 * so fat-chain should be synced with
				 * alloc-bitmap
				 */
				if (exfat_chain_cont_cluster(sb, ei->start_clu,
						num_clusters))
					return -EIO;
				ei->flags = ALLOC_FAT_CHAIN;
			}
			if (new_clu.flags == ALLOC_FAT_CHAIN)
				if (exfat_ent_set(sb, last_clu, new_clu.dir))
					return -EIO;
		}

		*clu = new_clu.dir;

		inode->i_blocks += EXFAT_CLU_TO_B(num_to_be_allocated, sbi) >> 9;

		/*
		 * Move *clu pointer along FAT chains (hole care) because the
		 * caller of this function expect *clu to be the last cluster.
		 * This only works when num_to_be_allocated >= 2,
		 * *clu = (the first cluster of the allocated chain) =>
		 * (the last cluster of ...)
		 */
		if (exfat_cluster_walk(sb, clu, num_to_be_allocated - 1, ei->flags))
			return -EIO;
		*count = 1;
	}

	/* hint information */
	ei->hint_bmap.off = local_clu_offset;
	ei->hint_bmap.clu = *clu;

	return 0;
}

static int exfat_get_block(struct inode *inode, sector_t iblock,
		struct buffer_head *bh_result, int create)
{
	struct exfat_inode_info *ei = EXFAT_I(inode);
	struct super_block *sb = inode->i_sb;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
	int err = 0;
	unsigned long mapped_blocks = 0;
	unsigned int cluster, sec_offset, count;
	sector_t last_block;
	sector_t phys = 0;
	sector_t valid_blks;
	loff_t i_size;

	mutex_lock(&sbi->s_lock);
	i_size = i_size_read(inode);
	last_block = EXFAT_B_TO_BLK_ROUND_UP(i_size, sb);
	if (iblock >= last_block && !create)
		goto done;

	/* Is this block already allocated? */
	count = EXFAT_B_TO_CLU_ROUND_UP(bh_result->b_size, sbi);
	err = exfat_map_cluster(inode, iblock >> sbi->sect_per_clus_bits,
			&cluster, &count, create);
	if (err) {
		if (err != -ENOSPC)
			exfat_fs_error_ratelimit(sb,
				"failed to bmap (inode : %p iblock : %llu, err : %d)",
				inode, (unsigned long long)iblock, err);
		goto unlock_ret;
	}

	if (cluster == EXFAT_EOF_CLUSTER)
		goto done;

	/* sector offset in cluster */
	sec_offset = iblock & (sbi->sect_per_clus - 1);

	phys = exfat_cluster_to_sector(sbi, cluster) + sec_offset;
	mapped_blocks = ((unsigned long)count << sbi->sect_per_clus_bits) - sec_offset;
	max_blocks = min(mapped_blocks, max_blocks);

	map_bh(bh_result, sb, phys);
	if (buffer_delay(bh_result))
		clear_buffer_delay(bh_result);

	/*
	 * In most cases, we just need to set bh_result to mapped, unmapped
	 * or new status as follows:
	 *  1. i_size == valid_size
	 *  2. write case (create == 1)
	 *  3. direct_read (!bh_result->b_folio)
	 *     -> the unwritten part will be zeroed in exfat_direct_IO()
	 *
	 * Otherwise, in the case of buffered read, it is necessary to take
	 * care the last nested block if valid_size is not equal to i_size.
	 */
	if (i_size == ei->valid_size || create || !bh_result->b_folio)
		valid_blks = EXFAT_B_TO_BLK_ROUND_UP(ei->valid_size, sb);
	else
		valid_blks = EXFAT_B_TO_BLK(ei->valid_size, sb);

	/* The range has been fully written, map it */
	if (iblock + max_blocks < valid_blks)
		goto done;

	/* The range has been partially written, map the written part */
	if (iblock < valid_blks) {
		max_blocks = valid_blks - iblock;
		goto done;
	}

	/* The area has not been written, map and mark as new for create case */
	if (create) {
		set_buffer_new(bh_result);
		ei->valid_size = EXFAT_BLK_TO_B(iblock + max_blocks, sb);
		mark_inode_dirty(inode);
		goto done;
	}

	/*
	 * The area has just one block partially written.
	 * In that case, we should read and fill the unwritten part of
	 * a block with zero.
	 */
	if (bh_result->b_folio && iblock == valid_blks &&
	    (ei->valid_size & (sb->s_blocksize - 1))) {
		loff_t size, pos;
		void *addr;

		max_blocks = 1;

		/*
		 * No buffer_head is allocated.
		 * (1) bmap: It's enough to set blocknr without I/O.
		 * (2) read: The unwritten part should be filled with zero.
		 *           If a folio does not have any buffers,
		 *           let's returns -EAGAIN to fallback to
		 *           block_read_full_folio() for per-bh IO.
		 */
		if (!folio_buffers(bh_result->b_folio)) {
			err = -EAGAIN;
			goto done;
		}

		pos = EXFAT_BLK_TO_B(iblock, sb);
		size = ei->valid_size - pos;
		addr = folio_address(bh_result->b_folio) +
			offset_in_folio(bh_result->b_folio, pos);

		/* Check if bh->b_data points to proper addr in folio */
		if (bh_result->b_data != addr) {
			exfat_fs_error_ratelimit(sb,
					"b_data(%p) != folio_addr(%p)",
					bh_result->b_data, addr);
			err = -EINVAL;
			goto done;
		}

		/* Read a block */
		err = bh_read(bh_result, 0);
		if (err < 0)
			goto done;

		/* Zero unwritten part of a block */
		memset(bh_result->b_data + size, 0, bh_result->b_size - size);
		err = 0;
		goto done;
	}

	/*
	 * The area has not been written, clear mapped for read/bmap cases.
	 * If so, it will be filled with zero without reading from disk.
	 */
	clear_buffer_mapped(bh_result);
done:
	bh_result->b_size = EXFAT_BLK_TO_B(max_blocks, sb);
	if (err < 0)
		clear_buffer_mapped(bh_result);
unlock_ret:
	mutex_unlock(&sbi->s_lock);
	return err;
}

static int exfat_read_folio(struct file *file, struct folio *folio)
{
	return mpage_read_folio(folio, exfat_get_block);
}

static void exfat_readahead(struct readahead_control *rac)
{
	struct address_space *mapping = rac->mapping;
	struct inode *inode = mapping->host;
	struct exfat_inode_info *ei = EXFAT_I(inode);
	loff_t pos = readahead_pos(rac);

	/* Range cross valid_size, read it page by page. */
	if (ei->valid_size < i_size_read(inode) &&
	    pos <= ei->valid_size &&
	    ei->valid_size < pos + readahead_length(rac))
		return;

	mpage_readahead(rac, exfat_get_block);
}

static int exfat_writepages(struct address_space *mapping,
		struct writeback_control *wbc)
{
	if (unlikely(exfat_forced_shutdown(mapping->host->i_sb)))
		return -EIO;

	return mpage_writepages(mapping, wbc, exfat_get_block);
}

static void exfat_write_failed(struct address_space *mapping, loff_t to)
{
	struct inode *inode = mapping->host;

	if (to > i_size_read(inode)) {
		truncate_pagecache(inode, i_size_read(inode));
		inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
		exfat_truncate(inode);
	}
}

static int exfat_write_begin(const struct kiocb *iocb,
			     struct address_space *mapping,
			     loff_t pos, unsigned int len,
			     struct folio **foliop, void **fsdata)
{
	int ret;

	if (unlikely(exfat_forced_shutdown(mapping->host->i_sb)))
		return -EIO;

	ret = block_write_begin(mapping, pos, len, foliop, exfat_get_block);

	if (ret < 0)
		exfat_write_failed(mapping, pos+len);

	return ret;
}

static int exfat_write_end(const struct kiocb *iocb,
			   struct address_space *mapping,
			   loff_t pos, unsigned int len, unsigned int copied,
			   struct folio *folio, void *fsdata)
{
	struct inode *inode = mapping->host;
	struct exfat_inode_info *ei = EXFAT_I(inode);
	int err;

	err = generic_write_end(iocb, mapping, pos, len, copied, folio, fsdata);
	if (err < len)
		exfat_write_failed(mapping, pos+len);

	if (!(err < 0) && pos + err > ei->valid_size) {
		ei->valid_size = pos + err;
		mark_inode_dirty(inode);
	}

	if (!(err < 0) && !(ei->attr & EXFAT_ATTR_ARCHIVE)) {
		inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
		ei->attr |= EXFAT_ATTR_ARCHIVE;
		mark_inode_dirty(inode);
	}

	return err;
}

static ssize_t exfat_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
{
	struct address_space *mapping = iocb->ki_filp->f_mapping;
	struct inode *inode = mapping->host;
	struct exfat_inode_info *ei = EXFAT_I(inode);
	loff_t pos = iocb->ki_pos;
	loff_t size = pos + iov_iter_count(iter);
	int rw = iov_iter_rw(iter);
	ssize_t ret;

	/*
	 * Need to use the DIO_LOCKING for avoiding the race
	 * condition of exfat_get_block() and ->truncate().
	 */
	ret = blockdev_direct_IO(iocb, inode, iter, exfat_get_block);
	if (ret < 0) {
		if (rw == WRITE && ret != -EIOCBQUEUED)
			exfat_write_failed(mapping, size);

		return ret;
	}

	size = pos + ret;

	if (rw == WRITE) {
		/*
		 * If the block had been partially written before this write,
		 * ->valid_size will not be updated in exfat_get_block(),
		 * update it here.
		 */
		if (ei->valid_size < size) {
			ei->valid_size = size;
			mark_inode_dirty(inode);
		}
	} else if (pos < ei->valid_size && ei->valid_size < size) {
		/* zero the unwritten part in the partially written block */
		iov_iter_revert(iter, size - ei->valid_size);
		iov_iter_zero(size - ei->valid_size, iter);
	}

	return ret;
}

static sector_t exfat_aop_bmap(struct address_space *mapping, sector_t block)
{
	sector_t blocknr;

	/* exfat_get_cluster() assumes the requested blocknr isn't truncated. */
	down_read(&EXFAT_I(mapping->host)->truncate_lock);
	blocknr = generic_block_bmap(mapping, block, exfat_get_block);
	up_read(&EXFAT_I(mapping->host)->truncate_lock);
	return blocknr;
}

/*
 * exfat_block_truncate_page() zeroes out a mapping from file offset `from'
 * up to the end of the block which corresponds to `from'.
 * This is required during truncate to physically zeroout the tail end
 * of that block so it doesn't yield old data if the file is later grown.
 * Also, avoid causing failure from fsx for cases of "data past EOF"
 */
int exfat_block_truncate_page(struct inode *inode, loff_t from)
{
	return block_truncate_page(inode->i_mapping, from, exfat_get_block);
}

static const struct address_space_operations exfat_aops = {
	.dirty_folio	= block_dirty_folio,
	.invalidate_folio = block_invalidate_folio,
	.read_folio	= exfat_read_folio,
	.readahead	= exfat_readahead,
	.writepages	= exfat_writepages,
	.write_begin	= exfat_write_begin,
	.write_end	= exfat_write_end,
	.direct_IO	= exfat_direct_IO,
	.bmap		= exfat_aop_bmap,
	.migrate_folio	= buffer_migrate_folio,
};

static inline unsigned long exfat_hash(loff_t i_pos)
{
	return hash_32(i_pos, EXFAT_HASH_BITS);
}

void exfat_hash_inode(struct inode *inode, loff_t i_pos)
{
	struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
	struct hlist_head *head = sbi->inode_hashtable + exfat_hash(i_pos);

	spin_lock(&sbi->inode_hash_lock);
	EXFAT_I(inode)->i_pos = i_pos;
	hlist_add_head(&EXFAT_I(inode)->i_hash_fat, head);
	spin_unlock(&sbi->inode_hash_lock);
}

void exfat_unhash_inode(struct inode *inode)
{
	struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);

	spin_lock(&sbi->inode_hash_lock);
	hlist_del_init(&EXFAT_I(inode)->i_hash_fat);
	EXFAT_I(inode)->i_pos = 0;
	spin_unlock(&sbi->inode_hash_lock);
}

struct inode *exfat_iget(struct super_block *sb, loff_t i_pos)
{
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	struct exfat_inode_info *info;
	struct hlist_head *head = sbi->inode_hashtable + exfat_hash(i_pos);
	struct inode *inode = NULL;

	spin_lock(&sbi->inode_hash_lock);
	hlist_for_each_entry(info, head, i_hash_fat) {
		WARN_ON(info->vfs_inode.i_sb != sb);

		if (i_pos != info->i_pos)
			continue;
		inode = igrab(&info->vfs_inode);
		if (inode)
			break;
	}
	spin_unlock(&sbi->inode_hash_lock);
	return inode;
}

/* doesn't deal with root inode */
static int exfat_fill_inode(struct inode *inode, struct exfat_dir_entry *info)
{
	struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
	struct exfat_inode_info *ei = EXFAT_I(inode);
	loff_t size = info->size;

	ei->dir = info->dir;
	ei->entry = info->entry;
	ei->attr = info->attr;
	ei->start_clu = info->start_clu;
	ei->flags = info->flags;
	ei->type = info->type;
	ei->valid_size = info->valid_size;

	ei->version = 0;
	ei->hint_stat.eidx = 0;
	ei->hint_stat.clu = info->start_clu;
	ei->hint_femp.eidx = EXFAT_HINT_NONE;
	ei->hint_bmap.off = EXFAT_EOF_CLUSTER;
	ei->i_pos = 0;

	inode->i_uid = sbi->options.fs_uid;
	inode->i_gid = sbi->options.fs_gid;
	inode_inc_iversion(inode);
	inode->i_generation = get_random_u32();

	if (info->attr & EXFAT_ATTR_SUBDIR) { /* directory */
		inode->i_generation &= ~1;
		inode->i_mode = exfat_make_mode(sbi, info->attr, 0777);
		inode->i_op = &exfat_dir_inode_operations;
		inode->i_fop = &exfat_dir_operations;
		set_nlink(inode, info->num_subdirs);
	} else { /* regular file */
		inode->i_generation |= 1;
		inode->i_mode = exfat_make_mode(sbi, info->attr, 0777);
		inode->i_op = &exfat_file_inode_operations;
		inode->i_fop = &exfat_file_operations;
		inode->i_mapping->a_ops = &exfat_aops;
		inode->i_mapping->nrpages = 0;
	}

	i_size_write(inode, size);

	exfat_save_attr(inode, info->attr);

	inode->i_blocks = round_up(i_size_read(inode), sbi->cluster_size) >> 9;
	inode_set_mtime_to_ts(inode, info->mtime);
	inode_set_ctime_to_ts(inode, info->mtime);
	ei->i_crtime = info->crtime;
	inode_set_atime_to_ts(inode, info->atime);

	return 0;
}

struct inode *exfat_build_inode(struct super_block *sb,
		struct exfat_dir_entry *info, loff_t i_pos)
{
	struct inode *inode;
	int err;

	inode = exfat_iget(sb, i_pos);
	if (inode)
		goto out;
	inode = new_inode(sb);
	if (!inode) {
		inode = ERR_PTR(-ENOMEM);
		goto out;
	}
	inode->i_ino = iunique(sb, EXFAT_ROOT_INO);
	inode_set_iversion(inode, 1);
	err = exfat_fill_inode(inode, info);
	if (err) {
		iput(inode);
		inode = ERR_PTR(err);
		goto out;
	}
	exfat_hash_inode(inode, i_pos);
	insert_inode_hash(inode);
out:
	return inode;
}

void exfat_evict_inode(struct inode *inode)
{
	truncate_inode_pages_final(&inode->i_data);

	if (!inode->i_nlink) {
		i_size_write(inode, 0);
		mutex_lock(&EXFAT_SB(inode->i_sb)->s_lock);
		__exfat_truncate(inode);
		mutex_unlock(&EXFAT_SB(inode->i_sb)->s_lock);
	}

	clear_inode(inode);
	exfat_cache_inval_inode(inode);
	exfat_unhash_inode(inode);
}