[PATCH] erofs: scan devices from device table

[Gao Xiang]

On Tue, May 10, 2022 at 05:35:11PM +0800, Jeffle Xu wrote:
> When "-o device" mount option is not specified, scan the device table
> and instantiate the devices if there's any in the device table. In this
> case, the tag field of each device slot uniquely specifies a device.
> 
> Signed-off-by: Jeffle Xu <jefflexu at linux.alibaba.com>
> ---
>  fs/erofs/erofs_fs.h |   9 ++--
>  fs/erofs/super.c    | 102 ++++++++++++++++++++++++++++++--------------
>  2 files changed, 72 insertions(+), 39 deletions(-)
> 
> diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
> index 1238ca104f09..1adde3a813b4 100644
> --- a/fs/erofs/erofs_fs.h
> +++ b/fs/erofs/erofs_fs.h
> @@ -37,12 +37,9 @@
>  #define EROFS_SB_EXTSLOT_SIZE	16
>  
>  struct erofs_deviceslot {
> -	union {
> -		u8 uuid[16];		/* used for device manager later */
> -		u8 userdata[64];	/* digest(sha256), etc. */
> -	} u;
> -	__le32 blocks;			/* total fs blocks of this device */
> -	__le32 mapped_blkaddr;		/* map starting at mapped_blkaddr */
> +	u8 tag[64];		/* digest(sha256), etc. */
> +	__le32 blocks;		/* total fs blocks of this device */
> +	__le32 mapped_blkaddr;	/* map starting at mapped_blkaddr */
>  	u8 reserved[56];
>  };
>  #define EROFS_DEVT_SLOT_SIZE	sizeof(struct erofs_deviceslot)
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index 4a623630e1c4..3f19c2031e69 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -219,7 +219,52 @@ static int erofs_load_compr_cfgs(struct super_block *sb,
>  }
>  #endif
>  
> -static int erofs_init_devices(struct super_block *sb,
> +static int erofs_init_device(struct erofs_buf *buf, struct super_block *sb,
> +			     struct erofs_device_info *dif, erofs_off_t *pos)
> +{
> +	struct erofs_sb_info *sbi = EROFS_SB(sb);
> +	struct erofs_deviceslot *dis;
> +	struct block_device *bdev;
> +	void *ptr;
> +	int ret;
> +
> +	ptr = erofs_read_metabuf(buf, sb, erofs_blknr(*pos), EROFS_KMAP);
> +	if (IS_ERR(ptr))
> +		return PTR_ERR(ptr);
> +	dis = ptr + erofs_blkoff(*pos);
> +
> +	if (!dif->path) {
> +		if (!dis->tag[0]) {
> +			erofs_err(sb, "Empty digest data (pos %llu)", *pos);

			erofs_err(sb, "empty tag @ pos %llu", *pos);
?

Otherwise it looks good to me,
Reviewed-by: Gao Xiang <hsiangkao at linux.alibaba.com>

Thanks,
Gao Xiang