net-memcg: pass in gfp_t mask to mem_cgroup_charge_skmem()

Add gfp_t mask as an input parameter to mem_cgroup_charge_skmem(),
to give more control to the networking stack and enable it to change
memcg charging behavior. In the future, the networking stack may decide
to avoid oom-kills when fallbacks are more appropriate.

One behavior change in mem_cgroup_charge_skmem() by this patch is to
avoid force charging by default and let the caller decide when and if
force charging is needed through the presence or absence of
__GFP_NOFAIL.

Signed-off-by: Wei Wang <weiwan@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 13 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8ef06f9e0db1..be585ceaba98 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -7048,14 +7048,14 @@ void mem_cgroup_sk_free(struct sock *sk)
  * mem_cgroup_charge_skmem - charge socket memory
  * @memcg: memcg to charge
  * @nr_pages: number of pages to charge
+ * @gfp_mask: reclaim mode
  *
  * Charges @nr_pages to @memcg. Returns %true if the charge fit within
- * @memcg's configured limit, %false if the charge had to be forced.
+ * @memcg's configured limit, %false if it doesn't.
  */
-bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
+bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages,
+			     gfp_t gfp_mask)
 {
-	gfp_t gfp_mask = GFP_KERNEL;
-
 	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) {
 		struct page_counter *fail;
 
@@ -7063,21 +7063,19 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
 			memcg->tcpmem_pressure = 0;
 			return true;
 		}
-		page_counter_charge(&memcg->tcpmem, nr_pages);
 		memcg->tcpmem_pressure = 1;
+		if (gfp_mask & __GFP_NOFAIL) {
+			page_counter_charge(&memcg->tcpmem, nr_pages);
+			return true;
+		}
 		return false;
 	}
 
-	/* Don't block in the packet receive path */
-	if (in_softirq())
-		gfp_mask = GFP_NOWAIT;
-
-	mod_memcg_state(memcg, MEMCG_SOCK, nr_pages);
-
-	if (try_charge(memcg, gfp_mask, nr_pages) == 0)
+	if (try_charge(memcg, gfp_mask, nr_pages) == 0) {
+		mod_memcg_state(memcg, MEMCG_SOCK, nr_pages);
 		return true;
+	}
 
-	try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages);
 	return false;
 }