issue:
in rwb_wrflush():
memmove(rwb->wrbuffer + padblocks * rwb->blocksize,
rwb->wrbuffer, rwb->wrnblocks * rwb->blocksize);
when the offest from rwb->wrblockstart to startblock plus rwb->wrnblocks is greater
than rwb->wralignblocks, it will be causing memory overflow since rwb->wrbuffer is
allocated rwb.wrmaxblock(rwb.wralignblocks) blocks.
fix:
Let us ensure that the wrblockstart in rwbuffer must be aligned according to
wralignblocks after writing, so there is no need to perform memmove when flushing
Signed-off-by: dongjiuzhu1 <dongjiuzhu1@xiaomi.com>