fs/erofs/data.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2017-2018 HUAWEI, Inc.
  *             https://www.huawei.com/
  * Copyright (C) 2021, Alibaba Cloud
  */
 #include "internal.h"
 #include <linux/prefetch.h>
 #include <linux/sched/mm.h>
 #include <linux/dax.h>
 #include <trace/events/erofs.h>

 void erofs_unmap_metabuf(struct erofs_buf *buf)
 {
 	if (buf->kmap_type == EROFS_KMAP)
 		kunmap_local(buf->base);
 	buf->base = NULL;
 	buf->kmap_type = EROFS_NO_KMAP;
 }

 void erofs_put_metabuf(struct erofs_buf *buf)
 {
 	if (!buf->page)
 		return;
 	erofs_unmap_metabuf(buf);
 	put_page(buf->page);
 	buf->page = NULL;
 }

 void *erofs_bread(struct erofs_buf *buf, struct inode *inode,
 		  erofs_blk_t blkaddr, enum erofs_kmap_type type)
 {
 	struct address_space *const mapping = inode->i_mapping;
 	erofs_off_t offset = blknr_to_addr(blkaddr);
 	pgoff_t index = offset >> PAGE_SHIFT;
 	struct page *page = buf->page;
 	struct folio *folio;
 	unsigned int nofs_flag;

 	if (!page || page->index != index) {
 		erofs_put_metabuf(buf);

 		nofs_flag = memalloc_nofs_save();
 		folio = read_cache_folio(mapping, index, NULL, NULL);
 		memalloc_nofs_restore(nofs_flag);
 		if (IS_ERR(folio))
 			return folio;

 		/* should already be PageUptodate, no need to lock page */
 		page = folio_file_page(folio, index);
 		buf->page = page;
 	}
 	if (buf->kmap_type == EROFS_NO_KMAP) {
 		if (type == EROFS_KMAP)
 			buf->base = kmap_local_page(page);
 		buf->kmap_type = type;
 	} else if (buf->kmap_type != type) {
 		DBG_BUGON(1);
 		return ERR_PTR(-EFAULT);
 	}
 	if (type == EROFS_NO_KMAP)
 		return NULL;
 	return buf->base + (offset & ~PAGE_MASK);
 }

 void *erofs_read_metabuf(struct erofs_buf *buf, struct super_block *sb,
 			 erofs_blk_t blkaddr, enum erofs_kmap_type type)
 {
 	if (erofs_is_fscache_mode(sb))
 		return erofs_bread(buf, EROFS_SB(sb)->s_fscache->inode,
 				   blkaddr, type);

 	return erofs_bread(buf, sb->s_bdev->bd_inode, blkaddr, type);
 }

 static int erofs_map_blocks_flatmode(struct inode *inode,
 				     struct erofs_map_blocks *map)
 {
 	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);

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

 	/* 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) {
 		map->m_pa = erofs_iloc(inode) + vi->inode_isize +
 			vi->xattr_isize + erofs_blkoff(offset);
 		map->m_plen = inode->i_size - offset;

 		/* inline data should be located in the same meta block */
 		if (erofs_blkoff(map->m_pa) + map->m_plen > EROFS_BLKSIZ) {
 			erofs_err(inode->i_sb,
 				  "inline data cross block boundary @ nid %llu",
 				  vi->nid);
 			DBG_BUGON(1);
 			return -EFSCORRUPTED;
 		}
 		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);
 		return -EIO;
 	}
 	return 0;
 }

 int erofs_map_blocks(struct inode *inode, struct erofs_map_blocks *map)
 {
 	struct super_block *sb = inode->i_sb;
 	struct erofs_inode *vi = EROFS_I(inode);
 	struct erofs_inode_chunk_index *idx;
 	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
 	u64 chunknr;
 	unsigned int unit;
 	erofs_off_t pos;
 	void *kaddr;
 	int err = 0;

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

 	if (vi->datalayout != EROFS_INODE_CHUNK_BASED) {
 		err = erofs_map_blocks_flatmode(inode, map);
 		goto out;
 	}

 	if (vi->chunkformat & EROFS_CHUNK_FORMAT_INDEXES)
 		unit = sizeof(*idx);			/* chunk index */
 	else
 		unit = EROFS_BLOCK_MAP_ENTRY_SIZE;	/* block map */

 	chunknr = map->m_la >> vi->chunkbits;
 	pos = ALIGN(erofs_iloc(inode) + vi->inode_isize +
 		    vi->xattr_isize, unit) + unit * chunknr;

 	kaddr = erofs_read_metabuf(&buf, sb, erofs_blknr(pos), EROFS_KMAP);
 	if (IS_ERR(kaddr)) {
 		err = PTR_ERR(kaddr);
 		goto out;
 	}
 	map->m_la = chunknr << vi->chunkbits;
 	map->m_plen = min_t(erofs_off_t, 1UL << vi->chunkbits,
 			    roundup(inode->i_size - map->m_la, EROFS_BLKSIZ));

 	/* handle block map */
 	if (!(vi->chunkformat & EROFS_CHUNK_FORMAT_INDEXES)) {
 		__le32 *blkaddr = kaddr + erofs_blkoff(pos);

 		if (le32_to_cpu(*blkaddr) == EROFS_NULL_ADDR) {
 			map->m_flags = 0;
 		} else {
 			map->m_pa = blknr_to_addr(le32_to_cpu(*blkaddr));
 			map->m_flags = EROFS_MAP_MAPPED;
 		}
 		goto out_unlock;
 	}
 	/* parse chunk indexes */
 	idx = kaddr + erofs_blkoff(pos);
 	switch (le32_to_cpu(idx->blkaddr)) {
 	case EROFS_NULL_ADDR:
 		map->m_flags = 0;
 		break;
 	default:
 		map->m_deviceid = le16_to_cpu(idx->device_id) &
 			EROFS_SB(sb)->device_id_mask;
 		map->m_pa = blknr_to_addr(le32_to_cpu(idx->blkaddr));
 		map->m_flags = EROFS_MAP_MAPPED;
 		break;
 	}
 out_unlock:
 	erofs_put_metabuf(&buf);
 out:
 	if (!err)
 		map->m_llen = map->m_plen;
 	trace_erofs_map_blocks_exit(inode, map, 0, err);
 	return err;
 }

 int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
 {
 	struct erofs_dev_context *devs = EROFS_SB(sb)->devs;
 	struct erofs_device_info *dif;
 	int id;

 	/* primary device by default */
 	map->m_bdev = sb->s_bdev;
 	map->m_daxdev = EROFS_SB(sb)->dax_dev;
 	map->m_dax_part_off = EROFS_SB(sb)->dax_part_off;
 	map->m_fscache = EROFS_SB(sb)->s_fscache;

 	if (map->m_deviceid) {
 		down_read(&devs->rwsem);
 		dif = idr_find(&devs->tree, map->m_deviceid - 1);
 		if (!dif) {
 			up_read(&devs->rwsem);
 			return -ENODEV;
 		}
 		map->m_bdev = dif->bdev;
 		map->m_daxdev = dif->dax_dev;
 		map->m_dax_part_off = dif->dax_part_off;
 		map->m_fscache = dif->fscache;
 		up_read(&devs->rwsem);
 	} else if (devs->extra_devices) {
 		down_read(&devs->rwsem);
 		idr_for_each_entry(&devs->tree, dif, id) {
 			erofs_off_t startoff, length;

 			if (!dif->mapped_blkaddr)
 				continue;
 			startoff = blknr_to_addr(dif->mapped_blkaddr);
 			length = blknr_to_addr(dif->blocks);

 			if (map->m_pa >= startoff &&
 			    map->m_pa < startoff + length) {
 				map->m_pa -= startoff;
 				map->m_bdev = dif->bdev;
 				map->m_daxdev = dif->dax_dev;
 				map->m_dax_part_off = dif->dax_part_off;
 				map->m_fscache = dif->fscache;
 				break;
 			}
 		}
 		up_read(&devs->rwsem);
 	}
 	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;
 	struct erofs_map_dev mdev;

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

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

 	mdev = (struct erofs_map_dev) {
 		.m_deviceid = map.m_deviceid,
 		.m_pa = map.m_pa,
 	};
 	ret = erofs_map_dev(inode->i_sb, &mdev);
 	if (ret)
 		return ret;

 	iomap->offset = map.m_la;
 	if (flags & IOMAP_DAX)
 		iomap->dax_dev = mdev.m_daxdev;
 	else
 		iomap->bdev = mdev.m_bdev;
 	iomap->length = map.m_llen;
 	iomap->flags = 0;
 	iomap->private = NULL;

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

 	if (map.m_flags & EROFS_MAP_META) {
 		void *ptr;
 		struct erofs_buf buf = __EROFS_BUF_INITIALIZER;

 		iomap->type = IOMAP_INLINE;
 		ptr = erofs_read_metabuf(&buf, inode->i_sb,
 					 erofs_blknr(mdev.m_pa), EROFS_KMAP);
 		if (IS_ERR(ptr))
 			return PTR_ERR(ptr);
 		iomap->inline_data = ptr + erofs_blkoff(mdev.m_pa);
 		iomap->private = buf.base;
 	} else {
 		iomap->type = IOMAP_MAPPED;
 		iomap->addr = mdev.m_pa;
 		if (flags & IOMAP_DAX)
 			iomap->addr += mdev.m_dax_part_off;
 	}
 	return 0;
 }

 static int erofs_iomap_end(struct inode *inode, loff_t pos, loff_t length,
 		ssize_t written, unsigned int flags, struct iomap *iomap)
 {
 	void *ptr = iomap->private;

 	if (ptr) {
 		struct erofs_buf buf = {
 			.page = kmap_to_page(ptr),
 			.base = ptr,
 			.kmap_type = EROFS_KMAP,
 		};

 		DBG_BUGON(iomap->type != IOMAP_INLINE);
 		erofs_put_metabuf(&buf);
 	} else {
 		DBG_BUGON(iomap->type == IOMAP_INLINE);
 	}
 	return written;
 }

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

 int erofs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		 u64 start, u64 len)
 {
 	if (erofs_inode_is_data_compressed(EROFS_I(inode)->datalayout)) {
 #ifdef CONFIG_EROFS_FS_ZIP
 		return iomap_fiemap(inode, fieinfo, start, len,
 				    &z_erofs_iomap_report_ops);
 #else
 		return -EOPNOTSUPP;
 #endif
 	}
 	return iomap_fiemap(inode, fieinfo, start, len, &erofs_iomap_ops);
 }

 /*
  * since we dont have write or truncate flows, so no inode
  * locking needs to be held at the moment.
  */
 static int erofs_read_folio(struct file *file, struct folio *folio)
 {
 	return iomap_read_folio(folio, &erofs_iomap_ops);
 }

 static void erofs_readahead(struct readahead_control *rac)
 {
 	return iomap_readahead(rac, &erofs_iomap_ops);
 }

 static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
 {
 	return iomap_bmap(mapping, block, &erofs_iomap_ops);
 }

 static ssize_t erofs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);

 	/* 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(inode))
 		return dax_iomap_rw(iocb, to, &erofs_iomap_ops);
 #endif
 	if (iocb->ki_flags & IOCB_DIRECT) {
 		struct block_device *bdev = inode->i_sb->s_bdev;
 		unsigned int blksize_mask;

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

 		if ((iocb->ki_pos | iov_iter_count(to) |
 		     iov_iter_alignment(to)) & blksize_mask)
 			return -EINVAL;

 		return iomap_dio_rw(iocb, to, &erofs_iomap_ops,
 				    NULL, 0, NULL, 0);
 	}
 	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 = {
 	.read_folio = erofs_read_folio,
 	.readahead = erofs_readahead,
 	.bmap = erofs_bmap,
 	.direct_IO = noop_direct_IO,
 	.release_folio = iomap_release_folio,
 	.invalidate_folio = iomap_invalidate_folio,
 };

 #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;
 	vm_flags_set(vma, 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,
 };
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2017-2018 HUAWEI, Inc.
	* https://www.huawei.com/
	* Copyright (C) 2021, Alibaba Cloud
	*/
	#include "internal.h"
	#include <linux/prefetch.h>
	#include <linux/sched/mm.h>
	#include <linux/dax.h>
	#include <trace/events/erofs.h>

	void erofs_unmap_metabuf(struct erofs_buf *buf)
	{
	if (buf->kmap_type == EROFS_KMAP)
	kunmap_local(buf->base);
	buf->base = NULL;
	buf->kmap_type = EROFS_NO_KMAP;
	}

	void erofs_put_metabuf(struct erofs_buf *buf)
	{
	if (!buf->page)
	return;
	erofs_unmap_metabuf(buf);
	put_page(buf->page);
	buf->page = NULL;
	}

	void erofs_bread(struct erofs_buf buf, struct inode *inode,
	erofs_blk_t blkaddr, enum erofs_kmap_type type)
	{
	struct address_space *const mapping = inode->i_mapping;
	erofs_off_t offset = blknr_to_addr(blkaddr);
	pgoff_t index = offset >> PAGE_SHIFT;
	struct page *page = buf->page;
	struct folio *folio;
	unsigned int nofs_flag;

	if (!page \|\| page->index != index) {
	erofs_put_metabuf(buf);

	nofs_flag = memalloc_nofs_save();
	folio = read_cache_folio(mapping, index, NULL, NULL);
	memalloc_nofs_restore(nofs_flag);
	if (IS_ERR(folio))
	return folio;

	/* should already be PageUptodate, no need to lock page */
	page = folio_file_page(folio, index);
	buf->page = page;
	}
	if (buf->kmap_type == EROFS_NO_KMAP) {
	if (type == EROFS_KMAP)
	buf->base = kmap_local_page(page);
	buf->kmap_type = type;
	} else if (buf->kmap_type != type) {
	DBG_BUGON(1);
	return ERR_PTR(-EFAULT);
	}
	if (type == EROFS_NO_KMAP)
	return NULL;
	return buf->base + (offset & ~PAGE_MASK);
	}

	void erofs_read_metabuf(struct erofs_buf buf, struct super_block *sb,
	erofs_blk_t blkaddr, enum erofs_kmap_type type)
	{
	if (erofs_is_fscache_mode(sb))
	return erofs_bread(buf, EROFS_SB(sb)->s_fscache->inode,
	blkaddr, type);

	return erofs_bread(buf, sb->s_bdev->bd_inode, blkaddr, type);
	}

	static int erofs_map_blocks_flatmode(struct inode *inode,
	struct erofs_map_blocks *map)
	{
	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);

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

	/* 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) {
	map->m_pa = erofs_iloc(inode) + vi->inode_isize +
	vi->xattr_isize + erofs_blkoff(offset);
	map->m_plen = inode->i_size - offset;

	/* inline data should be located in the same meta block */
	if (erofs_blkoff(map->m_pa) + map->m_plen > EROFS_BLKSIZ) {
	erofs_err(inode->i_sb,
	"inline data cross block boundary @ nid %llu",
	vi->nid);
	DBG_BUGON(1);
	return -EFSCORRUPTED;
	}
	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);
	return -EIO;
	}
	return 0;
	}

	int erofs_map_blocks(struct inode inode, struct erofs_map_blocks map)
	{
	struct super_block *sb = inode->i_sb;
	struct erofs_inode *vi = EROFS_I(inode);
	struct erofs_inode_chunk_index *idx;
	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
	u64 chunknr;
	unsigned int unit;
	erofs_off_t pos;
	void *kaddr;
	int err = 0;

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

	if (vi->datalayout != EROFS_INODE_CHUNK_BASED) {
	err = erofs_map_blocks_flatmode(inode, map);
	goto out;
	}

	if (vi->chunkformat & EROFS_CHUNK_FORMAT_INDEXES)
	unit = sizeof(idx); / chunk index */
	else
	unit = EROFS_BLOCK_MAP_ENTRY_SIZE; /* block map */

	chunknr = map->m_la >> vi->chunkbits;
	pos = ALIGN(erofs_iloc(inode) + vi->inode_isize +
	vi->xattr_isize, unit) + unit * chunknr;

	kaddr = erofs_read_metabuf(&buf, sb, erofs_blknr(pos), EROFS_KMAP);
	if (IS_ERR(kaddr)) {
	err = PTR_ERR(kaddr);
	goto out;
	}
	map->m_la = chunknr << vi->chunkbits;
	map->m_plen = min_t(erofs_off_t, 1UL << vi->chunkbits,
	roundup(inode->i_size - map->m_la, EROFS_BLKSIZ));

	/* handle block map */
	if (!(vi->chunkformat & EROFS_CHUNK_FORMAT_INDEXES)) {
	__le32 *blkaddr = kaddr + erofs_blkoff(pos);

	if (le32_to_cpu(*blkaddr) == EROFS_NULL_ADDR) {
	map->m_flags = 0;
	} else {
	map->m_pa = blknr_to_addr(le32_to_cpu(*blkaddr));
	map->m_flags = EROFS_MAP_MAPPED;
	}
	goto out_unlock;
	}
	/* parse chunk indexes */
	idx = kaddr + erofs_blkoff(pos);
	switch (le32_to_cpu(idx->blkaddr)) {
	case EROFS_NULL_ADDR:
	map->m_flags = 0;
	break;
	default:
	map->m_deviceid = le16_to_cpu(idx->device_id) &
	EROFS_SB(sb)->device_id_mask;
	map->m_pa = blknr_to_addr(le32_to_cpu(idx->blkaddr));
	map->m_flags = EROFS_MAP_MAPPED;
	break;
	}
	out_unlock:
	erofs_put_metabuf(&buf);
	out:
	if (!err)
	map->m_llen = map->m_plen;
	trace_erofs_map_blocks_exit(inode, map, 0, err);
	return err;
	}

	int erofs_map_dev(struct super_block sb, struct erofs_map_dev map)
	{
	struct erofs_dev_context *devs = EROFS_SB(sb)->devs;
	struct erofs_device_info *dif;
	int id;

	/* primary device by default */
	map->m_bdev = sb->s_bdev;
	map->m_daxdev = EROFS_SB(sb)->dax_dev;
	map->m_dax_part_off = EROFS_SB(sb)->dax_part_off;
	map->m_fscache = EROFS_SB(sb)->s_fscache;

	if (map->m_deviceid) {
	down_read(&devs->rwsem);
	dif = idr_find(&devs->tree, map->m_deviceid - 1);
	if (!dif) {
	up_read(&devs->rwsem);
	return -ENODEV;
	}
	map->m_bdev = dif->bdev;
	map->m_daxdev = dif->dax_dev;
	map->m_dax_part_off = dif->dax_part_off;
	map->m_fscache = dif->fscache;
	up_read(&devs->rwsem);
	} else if (devs->extra_devices) {
	down_read(&devs->rwsem);
	idr_for_each_entry(&devs->tree, dif, id) {
	erofs_off_t startoff, length;

	if (!dif->mapped_blkaddr)
	continue;
	startoff = blknr_to_addr(dif->mapped_blkaddr);
	length = blknr_to_addr(dif->blocks);

	if (map->m_pa >= startoff &&
	map->m_pa < startoff + length) {
	map->m_pa -= startoff;
	map->m_bdev = dif->bdev;
	map->m_daxdev = dif->dax_dev;
	map->m_dax_part_off = dif->dax_part_off;
	map->m_fscache = dif->fscache;
	break;
	}
	}
	up_read(&devs->rwsem);
	}
	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;
	struct erofs_map_dev mdev;

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

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

	mdev = (struct erofs_map_dev) {
	.m_deviceid = map.m_deviceid,
	.m_pa = map.m_pa,
	};
	ret = erofs_map_dev(inode->i_sb, &mdev);
	if (ret)
	return ret;

	iomap->offset = map.m_la;
	if (flags & IOMAP_DAX)
	iomap->dax_dev = mdev.m_daxdev;
	else
	iomap->bdev = mdev.m_bdev;
	iomap->length = map.m_llen;
	iomap->flags = 0;
	iomap->private = NULL;

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

	if (map.m_flags & EROFS_MAP_META) {
	void *ptr;
	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;

	iomap->type = IOMAP_INLINE;
	ptr = erofs_read_metabuf(&buf, inode->i_sb,
	erofs_blknr(mdev.m_pa), EROFS_KMAP);
	if (IS_ERR(ptr))
	return PTR_ERR(ptr);
	iomap->inline_data = ptr + erofs_blkoff(mdev.m_pa);
	iomap->private = buf.base;
	} else {
	iomap->type = IOMAP_MAPPED;
	iomap->addr = mdev.m_pa;
	if (flags & IOMAP_DAX)
	iomap->addr += mdev.m_dax_part_off;
	}
	return 0;
	}

	static int erofs_iomap_end(struct inode *inode, loff_t pos, loff_t length,
	ssize_t written, unsigned int flags, struct iomap *iomap)
	{
	void *ptr = iomap->private;

	if (ptr) {
	struct erofs_buf buf = {
	.page = kmap_to_page(ptr),
	.base = ptr,
	.kmap_type = EROFS_KMAP,
	};

	DBG_BUGON(iomap->type != IOMAP_INLINE);
	erofs_put_metabuf(&buf);
	} else {
	DBG_BUGON(iomap->type == IOMAP_INLINE);
	}
	return written;
	}

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

	int erofs_fiemap(struct inode inode, struct fiemap_extent_info fieinfo,
	u64 start, u64 len)
	{
	if (erofs_inode_is_data_compressed(EROFS_I(inode)->datalayout)) {
	#ifdef CONFIG_EROFS_FS_ZIP
	return iomap_fiemap(inode, fieinfo, start, len,
	&z_erofs_iomap_report_ops);
	#else
	return -EOPNOTSUPP;
	#endif
	}
	return iomap_fiemap(inode, fieinfo, start, len, &erofs_iomap_ops);
	}

	/*
	* since we dont have write or truncate flows, so no inode
	* locking needs to be held at the moment.
	*/
	static int erofs_read_folio(struct file file, struct folio folio)
	{
	return iomap_read_folio(folio, &erofs_iomap_ops);
	}

	static void erofs_readahead(struct readahead_control *rac)
	{
	return iomap_readahead(rac, &erofs_iomap_ops);
	}

	static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
	{
	return iomap_bmap(mapping, block, &erofs_iomap_ops);
	}

	static ssize_t erofs_file_read_iter(struct kiocb iocb, struct iov_iter to)
	{
	struct inode *inode = file_inode(iocb->ki_filp);

	/* 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(inode))
	return dax_iomap_rw(iocb, to, &erofs_iomap_ops);
	#endif
	if (iocb->ki_flags & IOCB_DIRECT) {
	struct block_device *bdev = inode->i_sb->s_bdev;
	unsigned int blksize_mask;

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

	if ((iocb->ki_pos \| iov_iter_count(to) \|
	iov_iter_alignment(to)) & blksize_mask)
	return -EINVAL;

	return iomap_dio_rw(iocb, to, &erofs_iomap_ops,
	NULL, 0, NULL, 0);
	}
	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 = {
	.read_folio = erofs_read_folio,
	.readahead = erofs_readahead,
	.bmap = erofs_bmap,
	.direct_IO = noop_direct_IO,
	.release_folio = iomap_release_folio,
	.invalidate_folio = iomap_invalidate_folio,
	};

	#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;
	vm_flags_set(vma, 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,
	};