From b9c565d5a29a795f970b4a1340393d8fc6722fb9 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 4 Mar 2008 14:29:11 -0800 Subject: [PATCH] memcg: remove clear_page_cgroup and atomics Remove clear_page_cgroup: it's an unhelpful helper, see for example how mem_cgroup_uncharge_page had to unlock_page_cgroup just in order to call it (serious races from that? I'm not sure). Once that's gone, you can see it's pointless for page_cgroup's ref_cnt to be atomic: it's always manipulated under lock_page_cgroup, except where force_empty unilaterally reset it to 0 (and how does uncharge's atomic_dec_and_test protect against that?). Simplify this page_cgroup locking: if you've got the lock and the pc is attached, then the ref_cnt must be positive: VM_BUG_ONs to check that, and to check that pc->page matches page (we're on the way to finding why sometimes it doesn't, but this patch doesn't fix that). Signed-off-by: Hugh Dickins Cc: David Rientjes Cc: Balbir Singh Acked-by: KAMEZAWA Hiroyuki Cc: Hirokazu Takahashi Cc: YAMAMOTO Takashi Cc: Paul Menage Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-format-patch failed