[PATCH RFC 1/1] f2fs: add per-device superblocks

From: Qiuyang Sun Currently, a multi-device F2FS only has superblocks written in its start device, but not the others. Thus, we cannot tell if a single device is part of a F2FS by reading itself only, which may be unsafe in scenarios like transferring devices between

[PATCH RFC 1/1] f2fs: add per-device superblocks

From: Qiuyang Sun Currently, a multi-device F2FS only has superblocks written in its start device, but not the others. Thus, we cannot tell if a single device is part of a F2FS by reading itself only, which may be unsafe in scenarios like transferring devices between computer systems. This patch