Re: [PATCH] xen-netback: correct success/error reporting for the SKB-with-fraglist case

On 24.02.2021 17:39, Paul Durrant wrote:

On 23/02/2021 16:29, Jan Beulich wrote:

quoted

When re-entering the main loop of xenvif_tx_check_gop() a 2nd time, the
special considerations for the head of the SKB no longer apply. Don't
mistakenly report ERROR to the frontend for the first entry in the list,
even if - from all I can tell - this shouldn't matter much as the overall
transmit will need to be considered failed anyway.

Signed-off-by: Jan Beulich <redacted>

--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c

@@ -499,7 +499,7 @@ check_frags:
  				 * the header's copy failed, and they are
  				 * sharing a slot, send an error
  				 */
-				if (i == 0 && sharedslot)
+				if (i == 0 && !first_shinfo && sharedslot)
  					xenvif_idx_release(queue, pending_idx,
  							   XEN_NETIF_RSP_ERROR);
  				else

I think this will DTRT, but to my mind it would make more sense to clear 
'sharedslot' before the 'goto check_frags' at the bottom of the function.

That was my initial idea as well, but
- I think it is for a reason that the variable is "const".
- There is another use of it which would then instead need further
  amending (and which I believe is at least part of the reason for
  the variable to be "const").

Jan