public long blockStart(long value) {
        return value & fsBlockNotMask;
    }
Given <tt>value</tt>, find the largest number less than or equal
to <tt>value</tt> which is a multiple of the fs block size.

@param value
@return The largest number less than or equal to <tt>value</tt>
which is a multiple of the soft block size
s3stream/src/main/java/com/automq/stream/thirdparty/moe/cnkirito/kdio/DirectIOLib.java