解決方法：在生成UBIFS image時加個-F參數即可

What is the the purpose of the -F (--space-fixup) mkfs.ubifs option?

Because of subtle ECC errors that can arise when programming NAND flash (see here), ubiformat is the recommended way of flashing a UBI image which contains a UBIFS file system. However, this is not always possible - for example, some embedded devices are manufactured using an industrial NAND flash programmer which has no knowledge of UBI or UBIFS.

The -F option causes mkfs.ubifs to set a special flag in the superblock, which triggers a "free space fixup" procedure in the kernel the very first time the filesystem is mounted. This fixup procedure involves finding all empty pages in the UBIFS file system and re-erasing them. This ensures that NAND pages which contain all 0xFF data get fully erased, which removes any problematic non-0xFF data from their OOB areas.

Of course it is not possible to re-erase individual NAND pages, and entire PEBs are erased. UBIFS performs this procedure by reading the useful (non 0xFF'ed) contents of LEBs and then invoking the atomic LEB change UBI operation. Obviously, this means that UBIFS has to read and write a lot of LEBs which takes time. But this happens only once, and the "free space fixup" procedure then unsets the "fixup" UBIFS superblock flag.

This option is supported if you are running a kernel version 3.0 or higher, or if you have pulled the changes from a UBIFS back-port tree. Note that ubiformat is still the preferred flashing method if the image is not being flashed for the first time, since it preserves existing erase counters (while using nandwrite or its equivalent does not).

Reference:

http://www.linux-mtd.infradead.org/faq/ubifs.html#L_free_space_fixup