what is meant "seg fs" in the linux kernel bootsect.s file - c

Question

When I reading the early Linux kernel code, I encountered a problem in boot/bootsect.s that was difficult to understanding."seg fs" ,What is it doing? If I want to change to AT&T's assembly syntax, How should I do!
go: mov ax,cs
mov dx,#0x4000-12 ! 0x4000 is arbitrary value >= length of
! bootsect + length of setup + room for stack
! 12 is disk parm size
! bde - changed 0xff00 to 0x4000 to use debugger at 0x6400 up (bde). We
! wouldn't have to worry about this if we checked the top of memory. Also
! my BIOS can be configured to put the wini drive tables in high memory
! instead of in the vector table. The old stack might have clobbered the
! drive table.
mov ds,ax
mov es,ax
mov ss,ax ! put stack at INITSEG:0x4000-12.
mov sp,dx
/*
* Many BIOS's default disk parameter tables will not
* recognize multi-sector reads beyond the maximum sector number
* specified in the default diskette parameter tables - this may
* mean 7 sectors in some cases.
*
* Since single sector reads are slow and out of the question,
* we must take care of this by creating new parameter tables
* (for the first disk) in RAM. We will set the maximum sector
* count to 18 - the most we will encounter on an HD 1.44.
*
* High doesn't hurt. Low does.
*
* Segments are as follows: ds=es=ss=cs - INITSEG,
* fs = 0, gs = parameter table segment
*/
push #0
pop fs
mov bx,#0x78 ! fs:bx is parameter table address
seg fs
lgs si,(bx) ! gs:si is source
mov di,dx ! es:di is destination
mov cx,#6 ! copy 12 bytes
cld
rep
seg gs
movsw
mov di,dx
movb 4(di),*18 ! patch sector count
seg fs
mov (bx),di
seg fs
mov 2(bx),es
mov ax,cs
mov fs,ax
mov gs,ax
xor ah,ah ! reset FDC
xor dl,dl
int 0x13

Answer 1

I assume it assembles as a fs prefix for the next instruction. That would match the comments, and is the only thing that makes sense.
Should be easy enough to build it and disassemble (into AT&T syntax if you want).
In AT&T syntax, you can just use fs as a prefix to other mnemonics.
fs movsw
assembles to this (in 64-bit mode. 16-bit mode would skip the 66 operand-size prefix).
0000000000000000 <.text>:
0: 64 66 a5 movsw %fs:(%rsi),%es:(%rdi)

Answer 2

who can tell me to change this to be correct or not? !
__go:
movw %cs , %ax
movw $0x4000-12 , %dx
movw %ax , %ds
movw %ax , %es
movw %ax , %ss
movw %dx , %sp
pushw $0x0000
popw %fs
movw $0x0078 , %bx
lgs %fs:(%bx) , %si
movw %dx , %di
movw $0x0006 , %cx
cld
rep
movw %dx , %di
movw $0x12 , 0x0004(%di)
movw %di , %fs:(%bx)
movw %es , %fs:0x0002(%bx)
movw %cs , %ax
movw %ax , %fs
movw %ax , %gs
xorb %ah , %ah
xorb %dl , %dl
int $0x13