erofs: support reading chunk-based uncompressed files

Add runtime support for chunk-based uncompressed files
described in the previous patch.

Link: https://lore.kernel.org/r/20210820100019.208490-2-hsiangkao@linux.alibaba.com
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

1 files changed, 80 insertions, 10 deletions

diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index 09c46fbdb9b2..9db829715652 100644
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -2,6 +2,7 @@
 /*
  * Copyright (C) 2017-2018 HUAWEI, Inc.
  *             https://www.huawei.com/
+ * Copyright (C) 2021, Alibaba Cloud
  */
 #include "internal.h"
 #include <linux/prefetch.h>
@@ -36,13 +37,6 @@ static int erofs_map_blocks_flatmode(struct inode *inode,
 	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;
 
@@ -77,14 +71,90 @@ static int erofs_map_blocks_flatmode(struct inode *inode,
 		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 int erofs_map_blocks(struct inode *inode,
+			    struct erofs_map_blocks *map, int flags)
+{
+	struct super_block *sb = inode->i_sb;
+	struct erofs_inode *vi = EROFS_I(inode);
+	struct erofs_inode_chunk_index *idx;
+	struct page *page;
+	u64 chunknr;
+	unsigned int unit;
+	erofs_off_t pos;
+	int err = 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)
+		return erofs_map_blocks_flatmode(inode, map, flags);
+
+	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(iloc(EROFS_SB(sb), vi->nid) + vi->inode_isize +
+		    vi->xattr_isize, unit) + unit * chunknr;
+
+	page = erofs_get_meta_page(inode->i_sb, erofs_blknr(pos));
+	if (IS_ERR(page))
+		return PTR_ERR(page);
+
+	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 = page_address(page) + 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 = page_address(page) + erofs_blkoff(pos);
+	switch (le32_to_cpu(idx->blkaddr)) {
+	case EROFS_NULL_ADDR:
+		map->m_flags = 0;
+		break;
+	default:
+		/* only one device is supported for now */
+		if (idx->device_id) {
+			erofs_err(sb, "invalid device id %u @ %llu for nid %llu",
+				  le16_to_cpu(idx->device_id),
+				  chunknr, vi->nid);
+			err = -EFSCORRUPTED;
+			goto out_unlock;
+		}
+		map->m_pa = blknr_to_addr(le32_to_cpu(idx->blkaddr));
+		map->m_flags = EROFS_MAP_MAPPED;
+		break;
+	}
+out_unlock:
+	unlock_page(page);
+	put_page(page);
+out:
+	map->m_llen = map->m_plen;
+	return err;
+}
+
 static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 		unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
 {
@@ -94,7 +164,7 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 	map.m_la = offset;
 	map.m_llen = length;
 
-	ret = erofs_map_blocks_flatmode(inode, &map, EROFS_GET_BLOCKS_RAW);
+	ret = erofs_map_blocks(inode, &map, EROFS_GET_BLOCKS_RAW);
 	if (ret < 0)
 		return ret;