[PATCH] erofs-utils: lib: fix chunk index reads from metabox

[Yifan Zhao <stopire@gmail.com>]

Chunk indexes stored in metabox are incorrectly read from the primary
device, resulting in incorrect file contents.

Assisted-by: Codex:gpt-6-astra
Signed-off-by: Yifan Zhao <stopire@gmail.com>
---
 lib/data.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/data.c b/lib/data.c
index 5a17af5..fa2907b 100644
--- a/lib/data.c
+++ b/lib/data.c
@@ -72,7 +72,7 @@ int __erofs_map_blocks(struct erofs_inode *inode,
 	struct erofs_sb_info *sbi = inode->sbi;
 	unsigned int unit, blksz = 1 << sbi->blkszbits;
 	struct erofs_inode_chunk_index *idx;
-	u8 buf[EROFS_MAX_BLOCK_SIZE];
+	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
 	erofs_blk_t startblk, addrmask, nblocks;
 	bool tailpacking;
 	erofs_off_t pos;
@@ -115,11 +115,10 @@ int __erofs_map_blocks(struct erofs_inode *inode,
 	pos = roundup(erofs_iloc(vi) + vi->inode_isize +
 		      vi->xattr_isize, unit) + unit * chunknr;
 
-	err = erofs_blk_read(sbi, 0, buf, erofs_blknr(sbi, pos), 1);
-	if (err < 0)
-		return -EIO;
-
-	idx = (void *)buf + erofs_blkoff(sbi, pos);
+	idx = erofs_read_metabuf(&buf, sbi, pos,
+				erofs_inode_in_metabox(vi));
+	if (IS_ERR(idx))
+		return PTR_ERR(idx);
 	map->m_la = chunknr << vi->u.chunkbits;
 	map->m_llen = min_t(erofs_off_t, 1ULL << vi->u.chunkbits,
 			    round_up(inode->i_size - map->m_la, blksz));
@@ -141,6 +140,7 @@ int __erofs_map_blocks(struct erofs_inode *inode,
 			map->m_flags = EROFS_MAP_MAPPED;
 		}
 	}
+	erofs_put_metabuf(&buf);
 out:
 	if (!err) {
 		map->m_plen = map->m_llen;
-- 
2.55.0