erofs: handle 48-bit blocks/uniaddr for extra devices

erofs_init_device() only reads blocks_lo and uniaddr_lo from the
on-disk device slot, ignoring blocks_hi and uniaddr_hi that were
introduced alongside the 48-bit block addressing feature.

For the primary device (dif0), erofs_read_superblock() already handles
this correctly by combining blocks_lo with blocks_hi when 48-bit
layout is enabled.  But the same logic was not applied to extra
devices.

With a 48-bit EROFS image using extra devices whose uniaddr or blocks
exceed 32-bit range, the truncated values cause erofs_map_dev() to
compute wrong physical addresses, leading to silent data corruption.

Fix this by reading blocks_hi and uniaddr_hi in erofs_init_device()
when 48-bit layout is enabled, consistent with the primary device
handling.  Also fix the erofs_deviceslot on-disk definition where
blocks_hi was incorrectly declared as __le32 instead of __le16.

Fixes: 61ba89b ("erofs: add 48-bit block addressing on-disk support")
Suggested-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Author: Zhan Xusheng

fs/erofs/erofs_fs.h

@@ -44,9 +44,9 @@ struct erofs_deviceslot {
 	u8 tag[64];		/* digest(sha256), etc. */
 	__le32 blocks_lo;	/* total blocks count of this device */
 	__le32 uniaddr_lo;	/* unified starting block of this device */
-	__le32 blocks_hi;	/* total blocks count MSB */
+	__le16 blocks_hi;	/* total blocks count MSB */
 	__le16 uniaddr_hi;	/* unified starting block MSB */
-	u8 reserved[50];
+	u8 reserved[52];
 };
 #define EROFS_DEVT_SLOT_SIZE	sizeof(struct erofs_deviceslot)
 

fs/erofs/super.c

@@ -129,6 +129,7 @@ static int erofs_init_device(struct erofs_buf *buf, struct super_block *sb,
 	struct erofs_fscache *fscache;
 	struct erofs_deviceslot *dis;
 	struct file *file;
+	bool _48bit;
 
 	dis = erofs_read_metabuf(buf, sb, *pos, false);
 	if (IS_ERR(dis))
@@ -175,8 +176,11 @@ static int erofs_init_device(struct erofs_buf *buf, struct super_block *sb,
 		dif->file = file;
 	}
 
-	dif->blocks = le32_to_cpu(dis->blocks_lo);
-	dif->uniaddr = le32_to_cpu(dis->uniaddr_lo);
+	_48bit = erofs_sb_has_48bit(sbi);
+	dif->blocks = le32_to_cpu(dis->blocks_lo) |
+		(_48bit ? (u64)le16_to_cpu(dis->blocks_hi) << 32 : 0);
+	dif->uniaddr = le32_to_cpu(dis->uniaddr_lo) |
+		(_48bit ? (u64)le16_to_cpu(dis->uniaddr_hi) << 32 : 0);
 	sbi->total_blocks += dif->blocks;
 	*pos += EROFS_DEVT_SLOT_SIZE;
 	return 0;