[PATCH erofs-utils v2 2/2] erofs-utils: handle 48-bit blocks/uniaddr for extra devices

[Gao Xiang]

On 2026/4/3 21:05, Zhan Xusheng wrote:
> erofs_write_device_table() only writes blocks_lo and uniaddr_lo to
> the on-disk device slot, but does not write blocks_hi or uniaddr_hi.
> Similarly, erofs_init_devices() only reads the _lo fields for extra
> devices.
> 
> For extra devices whose blocks or uniaddr exceed 32 bits in a 48-bit
> EROFS image, the upper bits are silently lost in both read and write
> paths.  This is inconsistent with the primary device handling, which
> correctly writes blocks_hi (super.c:231) and reads it (super.c:125).
> 
> Also sync the erofs_deviceslot on-disk definition with the kernel:
> blocks_hi should be __le16 (not __le32), matching the 48-bit design
> where all block address high parts are 16-bit.
> 
> A corresponding kernel fix has been applied:
>    ("erofs: handle 48-bit blocks/uniaddr for extra devices")
> 
> Signed-off-by: Zhan Xusheng <zhanxusheng at xiaomi.com>
> ---
>   include/erofs_fs.h |  4 ++--
>   lib/super.c        | 10 ++++++++--
>   2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/include/erofs_fs.h b/include/erofs_fs.h
> index ff8ac78..5d12049 100644
> --- a/include/erofs_fs.h
> +++ b/include/erofs_fs.h
> @@ -45,9 +45,9 @@ 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)
>   
> diff --git a/lib/super.c b/lib/super.c
> index 86d50a1..fd7972c 100644
> --- a/lib/super.c
> +++ b/lib/super.c
> @@ -54,6 +54,8 @@ static int erofs_init_devices(struct erofs_sb_info *sbi,
>   	if (!sbi->devs)
>   		return -ENOMEM;
>   	pos = le16_to_cpu(dsb->devt_slotoff) * EROFS_DEVT_SLOT_SIZE;
> +	bool _48bit = erofs_sb_has_48bit(sbi);

It should be refined with the variable definitions.

I will manually fix it up instead.

Thanks,
Gao Xiang