gianfar: Do not reuse pages from emergency reserve

[ Upstream commit 69fed99baac186013840ced3524562841296034f ]

A driver using dev_alloc_page() must not reuse a page that had to
use emergency memory reserve.

Otherwise all packets using this page will be immediately dropped,
unless for very specific sockets having SOCK_MEMALLOC bit set.

This issue might be hard to debug, because only a fraction of the RX
ring buffer would suffer from drops.

Fixes: 7535414 ("gianfar: Add paged allocation and Rx S/G")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Claudiu Manoil <claudiu.manoil@freescale.com>
Acked-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: edumazet

drivers/net/ethernet/freescale/gianfar.c

@@ -2939,7 +2939,7 @@ static bool gfar_add_rx_frag(struct gfar_rx_buff *rxb, u32 lstatus,
 				size, GFAR_RXB_TRUESIZE);
 
 	/* try reuse page */
-	if (unlikely(page_count(page) != 1))
+	if (unlikely(page_count(page) != 1 || page_is_pfmemalloc(page)))
 		return false;
 
 	/* change offset to the other half */