Commit 1461e8c2 authored Mar 22, 2022 by Shakeel Butt Committed by Linus Torvalds Mar 22, 2022

memcg: unify force charging conditions

Currently the kernel force charges the allocations which have __GFP_HIGH
flag without triggering the memory reclaim.  __GFP_HIGH indicates that
the caller is high priority and since commit 869712fd ("mm:
memcontrol: fix network errors from failing __GFP_ATOMIC charges") the
kernel lets such allocations do force charging.  Please note that
__GFP_ATOMIC has been replaced by __GFP_HIGH.

__GFP_HIGH does not tell if the caller can block or can trigger reclaim.
There are separate checks to determine that.  So, there is no need to
skip reclaiming for __GFP_HIGH allocations.  So, handle __GFP_HIGH
together with __GFP_NOFAIL which also does force charging.

Please note that this is a noop change as there are no __GFP_HIGH
allocators in the kernel which also have __GFP_ACCOUNT (or SLAB_ACCOUNT)
and does not allow reclaim for now.

Link: https://lkml.kernel.org/r/20220211064917.2028469-3-shakeelb@google.com


Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Chris Down <chris@chrisdown.name>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent becdf89d

mm/memcontrol.c

+7 −10

Original line number	Diff line number	Diff line
		@@ -2565,15 +2565,6 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
		goto retry;
		}

		/*
		* Memcg doesn't have a dedicated reserve for atomic
		* allocations. But like the global atomic pool, we need to
		* put the burden of reclaim on regular allocation requests
		* and let these go through as privileged allocations.
		*/
		if (gfp_mask & __GFP_ATOMIC)
		goto force;

		/*
		* Prevent unbounded recursion when reclaim operations need to
		* allocate memory. This might exceed the limits temporarily,
		@@ -2647,7 +2638,13 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
		goto retry;
		}
		nomem:
		if (!(gfp_mask & __GFP_NOFAIL))
		/*
		* Memcg doesn't have a dedicated reserve for atomic
		* allocations. But like the global atomic pool, we need to
		* put the burden of reclaim on regular allocation requests
		* and let these go through as privileged allocations.
		*/
		if (!(gfp_mask & (__GFP_NOFAIL \| __GFP_HIGH)))
		return -ENOMEM;
		force:
		/*