treewide: convert PF_MEMALLOC manipulations to new helpers

We now have memalloc_noreclaim_{save,restore} helpers for robust setting
and clearing of PF_MEMALLOC.  Let's convert the code which was using the
generic tsk_restore_flags().  No functional change.

[vbabka@suse.cz: in net/core/sock.c the hunk is missing]
Link: http://lkml.kernel.org/r/20170405074700.29871-4-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Josef Bacik <jbacik@fb.com>
Cc: Lee Duncan <lduncan@suse.com>
Cc: Chris Leech <cleech@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Wouter Verhelst <w@uter.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/net/core/dev.c b/net/core/dev.c
index 99924d1..96cf83d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -81,6 +81,7 @@
 #include <linux/hash.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <linux/sched/mm.h>
 #include <linux/mutex.h>
 #include <linux/string.h>
 #include <linux/mm.h>
@@ -4235,7 +4236,7 @@ static int __netif_receive_skb(struct sk_buff *skb)
 	int ret;
 
 	if (sk_memalloc_socks() && skb_pfmemalloc(skb)) {
-		unsigned long pflags = current->flags;
+		unsigned int noreclaim_flag;
 
 		/*
 		 * PFMEMALLOC skbs are special, they should
@@ -4246,9 +4247,9 @@ static int __netif_receive_skb(struct sk_buff *skb)
 		 * Use PF_MEMALLOC as this saves us from propagating the allocation
 		 * context down to all allocation sites.
 		 */
-		current->flags |= PF_MEMALLOC;
+		noreclaim_flag = memalloc_noreclaim_save();
 		ret = __netif_receive_skb_core(skb, true);
-		current_restore_flags(pflags, PF_MEMALLOC);
+		memalloc_noreclaim_restore(noreclaim_flag);
 	} else
 		ret = __netif_receive_skb_core(skb, false);