erofs: allow 16-byte volume name again

Actually, volume name doesn't need to include the NIL terminator if
the string length matches the on-disk field size as mentioned in [1].

I tend to relax it together with the upcoming 48-bit block addressing
(or stable kernels which backport this fix) so that we could have a
chance to record a 16-byte volume name like ext4.

Since in-memory `volume_name` has no user, just get rid of the unneeded
check for now.  `sbi->uuid` is useless and avoid it too.

[1] https://lore.kernel.org/r/96efe46b-dcce-4490-bba1-a0b00932d1cc@linux.alibaba.com

Fixes: a64d949 ("staging: erofs: refuse to mount images with malformed volume name")
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250225033934.2542635-1-hsiangkao@linux.alibaba.com

Author: hsiangkao

fs/erofs/internal.h

@@ -152,8 +152,6 @@ struct erofs_sb_info {
 	/* used for statfs, f_files - f_favail */
 	u64 inos;
 
-	u8 uuid[16];                    /* 128-bit uuid for volume */
-	u8 volume_name[16];             /* volume name */
 	u32 feature_compat;
 	u32 feature_incompat;
 

fs/erofs/super.c

@@ -317,14 +317,6 @@ static int erofs_read_superblock(struct super_block *sb)
 
 	super_set_uuid(sb, (void *)dsb->uuid, sizeof(dsb->uuid));
 
-	ret = strscpy(sbi->volume_name, dsb->volume_name,
-		      sizeof(dsb->volume_name));
-	if (ret < 0) {	/* -E2BIG */
-		erofs_err(sb, "bad volume name without NIL terminator");
-		ret = -EFSCORRUPTED;
-		goto out;
-	}
-
 	/* parse on-disk compression configurations */
 	ret = z_erofs_parse_cfgs(sb, dsb);
 	if (ret < 0)