FROMLIST: mm, memcg: add mem_cgroup_disabled checks in vmpressure and swap-related functions

Add mem_cgroup_disabled check in vmpressure, mem_cgroup_uncharge_swap and
cgroup_throttle_swaprate functions. This minimizes the memcg overhead in
the pagefault and exit_mmap paths when memcgs are disabled using
cgroup_disable=memory command-line option.
This change results in ~2.1% overhead reduction when running PFT test [1]
comparing {CONFIG_MEMCG=n, CONFIG_MEMCG_SWAP=n} against {CONFIG_MEMCG=y,
CONFIG_MEMCG_SWAP=y, cgroup_disable=memory} configuration on an 8-core
ARM64 Android device.

[1] https://lkml.org/lkml/2006/8/29/294 also used in mmtests suite

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>

Link: https://lore.kernel.org/patchwork/patch/1458906/
Bug: 191223209
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: Ic1fc75eb1e4d7a9848cf641b9f232ad3262c490b

mm/swapfile.c

@@ -3818,6 +3818,9 @@ void cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask)
 	struct swap_info_struct *si, *next;
 	int nid = page_to_nid(page);
 
+	if (mem_cgroup_disabled())
+		return;
+
 	if (!(gfp_mask & __GFP_IO))
 		return;