Re: [PATCH 3/7] tcp_conn: Avoid 7-bit hole in struct tcp_splice_conn

On Wed, 29 Jan 2025 12:02:09 +1100
David Gibson <david(a)gibson.dropbear.id.au> wrote:

...
  On Tue, Jan 28, 2025 at 07:48:33AM +0100, Stefano
Brivio wrote:
  On Tue, 28 Jan 2025 11:53:09 +1100
 David Gibson <david(a)gibson.dropbear.id.au> wrote:
   
  On Tue, Jan 28, 2025 at 12:15:28AM +0100, Stefano
Brivio wrote:  
  Moving in_epoll out of the common flow data
created a 7-bit hole in
 struct tcp_splice_conn: repack by shrinking @flags by one (otherwise
 unused) bit.     
 
 Is this actually necessary for the migration stuff?  Or just a cleanup
 you spotted along the way?   
 
 I thought it was helpful to keep the same size on 32-bit, but it looks
 like it's not actually needed.
 
 Let me drop it from this series as it's just noise and I'm trying to
 keep this slim. If we are all happy with it I can apply it. If not I'll
 forget about it.   
 
 Eh, I don't care that much either way.
 
 Note, btw, that bit-field packing is another way source and
 destination could potentially have mismatching data structures.  IIUC
 bit field packing is described by the ABI and doesn't necessarily
 match the byte endianness. 
Right, that's actually the reason that brought me to this change: I was
comparing stuff between x86_64 and armv6l. On the other hand, this part
of the specific ABI is generally considered stable so I can rely on it.

-- 
Stefano