On Fri, Apr 9, 2021 at 8:54 PM Jakub Kicinski <k...@kernel.org> wrote:
>
> On Fri, 9 Apr 2021 20:06:04 +0200 Matteo Croce wrote:
> > From: Matteo Croce <mcr...@microsoft.com>
> >
> > use the new helper macro skb_for_each_frag() which allows to iterate
> > through all the SKB fragments.
> >
> > The patch was created with Coccinelle, this was the semantic patch:
>
> Bunch of set but not used warnings here. Please make sure the code
> builds cleanly allmodconfig, W=1 C=1 before posting.
>
Will do.
> What pops to mind (although quite nit picky) is the question if the
> assembly changes much between driver which used to cache nr_frags and
> now always going skb_shinfo(skb)->nr_frags? It's a relatively common
> pattern.
Since skb_shinfo() is a macro and skb_end_pointer() a static inline,
it should be the same, but I was curious to check so, this is a diff
between the following snippet before and afer the macro:
int frags = skb_shinfo(skb)->nr_frags;
int i;
for (i = 0; i < frags; i++)
kfree(skb->frags[i]);
1 file changed, 8 insertions(+), 7 deletions(-)
--- ins1.s 2021-04-09 22:35:59.384523865 +0200
+++ ins2.s 2021-04-09 22:36:08.132594737 +0200
@@ -1,26 +1,27 @@
iter:
movsx rax, DWORD PTR [rdi+16]
mov rdx, QWORD PTR [rdi+8]
mov eax, DWORD PTR [rdx+rax]
test eax, eax
jle .L6
push rbp
- sub eax, 1
+ mov rbp, rdi
push rbx
- lea rbp, [rdi+32+rax*8]
- lea rbx, [rdi+24]
+ xor ebx, ebx
sub rsp, 8
.L3:
- mov rdi, QWORD PTR [rbx]
- add rbx, 8
+ mov rdi, QWORD PTR [rbp+24+rbx*8]
+ add rbx, 1
call kfree
- cmp rbx, rbp
- jne .L3
+ movsx rax, DWORD PTR [rbp+16]
+ mov rdx, QWORD PTR [rbp+8]
+ cmp DWORD PTR [rdx+rax], ebx
+ jg .L3
add rsp, 8
xor eax, eax
pop rbx
pop rbp
ret
.L6:
xor eax, eax
ret
--
per aspera ad upstream
