// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2017-2018 HUAWEI, Inc.
 *             https://www.huawei.com/
 */
#include "internal.h"
#include <linux/prefetch.h>
#include <linux/iomap.h>
#include <linux/dax.h>
#include <trace/events/erofs.h>

static void erofs_readendio(struct bio *bio)
{
	struct bio_vec *bvec;
	blk_status_t err = bio->bi_status;
	struct bvec_iter_all iter_all;

	bio_for_each_segment_all(bvec, bio, iter_all) {
		struct page *page = bvec->bv_page;

		/* page is already locked */
		DBG_BUGON(PageUptodate(page));

		if (err)
			SetPageError(page);
		else
			SetPageUptodate(page);

		unlock_page(page);
		/* page could be reclaimed now */
	}
	bio_put(bio);
}

struct page *erofs_get_meta_page(struct super_block *sb, erofs_blk_t blkaddr)
{
	struct address_space *const mapping = sb->s_bdev->bd_inode->i_mapping;
	struct page *page;

	page = read_cache_page_gfp(mapping, blkaddr,
				   mapping_gfp_constraint(mapping, ~__GFP_FS));
	/* should already be PageUptodate */
	if (!IS_ERR(page))
		lock_page(page);
	return page;
}

static int erofs_map_blocks_flatmode(struct inode *inode,
				     struct erofs_map_blocks *map,
				     int flags)
{
	int err = 0;
	erofs_blk_t nblocks, lastblk;
	u64 offset = map->m_la;
	struct erofs_inode *vi = EROFS_I(inode);
	bool tailendpacking = (vi->datalayout == EROFS_INODE_FLAT_INLINE);

	trace_erofs_map_blocks_flatmode_enter(inode, map, flags);

	nblocks = DIV_ROUND_UP(inode->i_size, PAGE_SIZE);
	lastblk = nblocks - tailendpacking;

	if (offset >= inode->i_size) {
		/* leave out-of-bound access unmapped */
		map->m_flags = 0;
		map->m_plen = 0;
		goto out;
	}

	/* there is no hole in flatmode */
	map->m_flags = EROFS_MAP_MAPPED;

	if (offset < blknr_to_addr(lastblk)) {
		map->m_pa = blknr_to_addr(vi->raw_blkaddr) + map->m_la;
		map->m_plen = blknr_to_addr(lastblk) - offset;
	} else if (tailendpacking) {
		/* 2 - inode inline B: inode, [xattrs], inline last blk... */
		struct erofs_sb_info *sbi = EROFS_SB(inode->i_sb);

		map->m_pa = iloc(sbi, vi->nid) + vi->inode_isize +
			vi->xattr_isize + erofs_blkoff(map->m_la);
		map->m_plen = inode->i_size - offset;

		/* inline data should be located in one meta block */
		if (erofs_blkoff(map->m_pa) + map->m_plen > PAGE_SIZE) {
			erofs_err(inode->i_sb,
				  "inline data cross block boundary @ nid %llu",
				  vi->nid);
			DBG_BUGON(1);
			err = -EFSCORRUPTED;
			goto err_out;
		}

		map->m_flags |= EROFS_MAP_META;
	} else {
		erofs_err(inode->i_sb,
			  "internal error @ nid: %llu (size %llu), m_la 0x%llx",
			  vi->nid, inode->i_size, map->m_la);
		DBG_BUGON(1);
		err = -EIO;
		goto err_out;
	}

out:
	map->m_llen = map->m_plen;

err_out:
	trace_erofs_map_blocks_flatmode_exit(inode, map, flags, 0);
	return err;
}

static inline struct bio *erofs_read_raw_page(struct bio *bio,
					      struct address_space *mapping,
					      struct page *page,
					      erofs_off_t *last_block,
					      unsigned int nblocks,
					      unsigned int *eblks,
					      bool ra)
{
	struct inode *const inode = mapping->host;
	struct super_block *const sb = inode->i_sb;
	erofs_off_t current_block = (erofs_off_t)page->index;
	int err;

	DBG_BUGON(!nblocks);

	if (PageUptodate(page)) {
		err = 0;
		goto has_updated;
	}

	/* note that for readpage case, bio also equals to NULL */
	if (bio &&
	    (*last_block + 1 != current_block || !*eblks)) {
submit_bio_retry:
		submit_bio(bio);
		bio = NULL;
	}

	if (!bio) {
		struct erofs_map_blocks map = {
			.m_la = blknr_to_addr(current_block),
		};
		erofs_blk_t blknr;
		unsigned int blkoff;

		err = erofs_map_blocks_flatmode(inode, &map, EROFS_GET_BLOCKS_RAW);
		if (err)
			goto err_out;

		/* zero out the holed page */
		if (!(map.m_flags & EROFS_MAP_MAPPED)) {
			zero_user_segment(page, 0, PAGE_SIZE);
			SetPageUptodate(page);

			/* imply err = 0, see erofs_map_blocks */
			goto has_updated;
		}

		/* for RAW access mode, m_plen must be equal to m_llen */
		DBG_BUGON(map.m_plen != map.m_llen);

		blknr = erofs_blknr(map.m_pa);
		blkoff = erofs_blkoff(map.m_pa);

		/* deal with inline page */
		if (map.m_flags & EROFS_MAP_META) {
			void *vsrc, *vto;
			struct page *ipage;

			DBG_BUGON(map.m_plen > PAGE_SIZE);

			ipage = erofs_get_meta_page(inode->i_sb, blknr);

			if (IS_ERR(ipage)) {
				err = PTR_ERR(ipage);
				goto err_out;
			}

			vsrc = kmap_atomic(ipage);
			vto = kmap_atomic(page);
			memcpy(vto, vsrc + blkoff, map.m_plen);
			memset(vto + map.m_plen, 0, PAGE_SIZE - map.m_plen);
			kunmap_atomic(vto);
			kunmap_atomic(vsrc);
			flush_dcache_page(page);

			SetPageUptodate(page);
			/* TODO: could we unlock the page earlier? */
			unlock_page(ipage);
			put_page(ipage);

			/* imply err = 0, see erofs_map_blocks */
			goto has_updated;
		}

		/* pa must be block-aligned for raw reading */
		DBG_BUGON(erofs_blkoff(map.m_pa));

		/* max # of continuous pages */
		if (nblocks > DIV_ROUND_UP(map.m_plen, PAGE_SIZE))
			nblocks = DIV_ROUND_UP(map.m_plen, PAGE_SIZE);

		*eblks = bio_max_segs(nblocks);
		bio = bio_alloc(GFP_NOIO, *eblks);

		bio->bi_end_io = erofs_readendio;
		bio_set_dev(bio, sb->s_bdev);
		bio->bi_iter.bi_sector = (sector_t)blknr <<
			LOG_SECTORS_PER_BLOCK;
		bio->bi_opf = REQ_OP_READ | (ra ? REQ_RAHEAD : 0);
	}

	err = bio_add_page(bio, page, PAGE_SIZE, 0);
	/* out of the extent or bio is full */
	if (err < PAGE_SIZE)
		goto submit_bio_retry;
	--*eblks;
	*last_block = current_block;
	return bio;

err_out:
	/* for sync reading, set page error immediately */
	if (!ra) {
		SetPageError(page);
		ClearPageUptodate(page);
	}
has_updated:
	unlock_page(page);

	/* if updated manually, continuous pages has a gap */
	if (bio)
		submit_bio(bio);
	return err ? ERR_PTR(err) : NULL;
}

/*
 * since we dont have write or truncate flows, so no inode
 * locking needs to be held at the moment.
 */
static int erofs_raw_access_readpage(struct file *file, struct page *page)
{
	erofs_off_t last_block;
	unsigned int eblks;
	struct bio *bio;

	trace_erofs_readpage(page, true);

	bio = erofs_read_raw_page(NULL, page->mapping,
				  page, &last_block, 1, &eblks, false);

	if (IS_ERR(bio))
		return PTR_ERR(bio);

	if (bio)
		submit_bio(bio);
	return 0;
}

static void erofs_raw_access_readahead(struct readahead_control *rac)
{
	erofs_off_t last_block;
	unsigned int eblks;
	struct bio *bio = NULL;
	struct page *page;

	trace_erofs_readpages(rac->mapping->host, readahead_index(rac),
			readahead_count(rac), true);

	while ((page = readahead_page(rac))) {
		prefetchw(&page->flags);

		bio = erofs_read_raw_page(bio, rac->mapping, page, &last_block,
				readahead_count(rac), &eblks, true);

		/* all the page errors are ignored when readahead */
		if (IS_ERR(bio)) {
			pr_err("%s, readahead error at page %lu of nid %llu\n",
			       __func__, page->index,
			       EROFS_I(rac->mapping->host)->nid);

			bio = NULL;
		}

		put_page(page);
	}

	if (bio)
		submit_bio(bio);
}

static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
{
	struct inode *inode = mapping->host;
	struct erofs_map_blocks map = {
		.m_la = blknr_to_addr(block),
	};

	if (EROFS_I(inode)->datalayout == EROFS_INODE_FLAT_INLINE) {
		erofs_blk_t blks = i_size_read(inode) >> LOG_BLOCK_SIZE;

		if (block >> LOG_SECTORS_PER_BLOCK >= blks)
			return 0;
	}

	if (!erofs_map_blocks_flatmode(inode, &map, EROFS_GET_BLOCKS_RAW))
		return erofs_blknr(map.m_pa);

	return 0;
}

static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
		unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
{
	int ret;
	struct erofs_map_blocks map;

	map.m_la = offset;
	map.m_llen = length;

	ret = erofs_map_blocks_flatmode(inode, &map, EROFS_GET_BLOCKS_RAW);
	if (ret < 0)
		return ret;

	iomap->bdev = inode->i_sb->s_bdev;
	iomap->dax_dev = EROFS_I_SB(inode)->dax_dev;
	iomap->offset = map.m_la;
	iomap->length = map.m_llen;
	iomap->flags = 0;

	if (!(map.m_flags & EROFS_MAP_MAPPED)) {
		iomap->type = IOMAP_HOLE;
		iomap->addr = IOMAP_NULL_ADDR;
		if (!iomap->length)
			iomap->length = length;
		return 0;
	}

	/* that shouldn't happen for now */
	if (map.m_flags & EROFS_MAP_META) {
		DBG_BUGON(1);
		return -ENOTBLK;
	}
	iomap->type = IOMAP_MAPPED;
	iomap->addr = map.m_pa;
	return 0;
}

static const struct iomap_ops erofs_iomap_ops = {
	.iomap_begin = erofs_iomap_begin,
};

static int erofs_prepare_dio(struct kiocb *iocb, struct iov_iter *to)
{
	struct inode *inode = file_inode(iocb->ki_filp);
	loff_t align = iocb->ki_pos | iov_iter_count(to) |
		iov_iter_alignment(to);
	struct block_device *bdev = inode->i_sb->s_bdev;
	unsigned int blksize_mask;

	if (bdev)
		blksize_mask = (1 << ilog2(bdev_logical_block_size(bdev))) - 1;
	else
		blksize_mask = (1 << inode->i_blkbits) - 1;

	if (align & blksize_mask)
		return -EINVAL;

	/*
	 * Temporarily fall back tail-packing inline to buffered I/O instead
	 * since tail-packing inline support relies on an iomap core update.
	 */
	if (EROFS_I(inode)->datalayout == EROFS_INODE_FLAT_INLINE &&
	    iocb->ki_pos + iov_iter_count(to) >
			rounddown(inode->i_size, EROFS_BLKSIZ))
		return 1;
	return 0;
}

static ssize_t erofs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
	/* no need taking (shared) inode lock since it's a ro filesystem */
	if (!iov_iter_count(to))
		return 0;

#ifdef CONFIG_FS_DAX
	if (IS_DAX(iocb->ki_filp->f_mapping->host))
		return dax_iomap_rw(iocb, to, &erofs_iomap_ops);
#endif
	if (iocb->ki_flags & IOCB_DIRECT) {
		int err = erofs_prepare_dio(iocb, to);

		if (!err)
			return iomap_dio_rw(iocb, to, &erofs_iomap_ops,
					    NULL, 0);
		if (err < 0)
			return err;
	}
	return filemap_read(iocb, to, 0);
}

/* for uncompressed (aligned) files and raw access for other files */
const struct address_space_operations erofs_raw_access_aops = {
	.readpage = erofs_raw_access_readpage,
	.readahead = erofs_raw_access_readahead,
	.bmap = erofs_bmap,
	.direct_IO = noop_direct_IO,
};

#ifdef CONFIG_FS_DAX
static vm_fault_t erofs_dax_huge_fault(struct vm_fault *vmf,
		enum page_entry_size pe_size)
{
	return dax_iomap_fault(vmf, pe_size, NULL, NULL, &erofs_iomap_ops);
}

static vm_fault_t erofs_dax_fault(struct vm_fault *vmf)
{
	return erofs_dax_huge_fault(vmf, PE_SIZE_PTE);
}

static const struct vm_operations_struct erofs_dax_vm_ops = {
	.fault		= erofs_dax_fault,
	.huge_fault	= erofs_dax_huge_fault,
};

static int erofs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
	if (!IS_DAX(file_inode(file)))
		return generic_file_readonly_mmap(file, vma);

	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
		return -EINVAL;

	vma->vm_ops = &erofs_dax_vm_ops;
	vma->vm_flags |= VM_HUGEPAGE;
	return 0;
}
#else
#define erofs_file_mmap	generic_file_readonly_mmap
#endif

const struct file_operations erofs_file_fops = {
	.llseek		= generic_file_llseek,
	.read_iter	= erofs_file_read_iter,
	.mmap		= erofs_file_mmap,
	.splice_read	= generic_file_splice_read,
};