[patch v2] mm, memcg: do not retry precharge charges

[David Rientjes]

When memory.move_charge_at_immigrate is enabled and precharges are
depleted during move, mem_cgroup_move_charge_pte_range() will attempt to
increase the size of the precharge.

This can be allowed to do reclaim, but should not call the oom killer to
oom kill a process.  It's better to fail the attach rather than oom kill
a process attached to the memcg hierarchy.

Prevent precharges from ever looping by setting __GFP_NORETRY.  This was
probably the intention of the GFP_KERNEL & ~__GFP_NORETRY, which is
pointless as written.

Fixes: 0029e19ebf84 ("mm: memcontrol: remove explicit OOM parameter in charge 
path")
Signed-off-by: David Rientjes <rient...@google.com>
---
 mm/memcontrol.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4353,9 +4353,12 @@ static int mem_cgroup_do_precharge(unsigned long count)
                return ret;
        }
 
-       /* Try charges one by one with reclaim */
+       /*
+        * Try charges one by one with reclaim, but do not retry.  This avoids
+        * calling the oom killer when the precharge should just fail.
+        */
        while (count--) {
-               ret = try_charge(mc.to, GFP_KERNEL & ~__GFP_NORETRY, 1);
+               ret = try_charge(mc.to, GFP_KERNEL | __GFP_NORETRY, 1);
                if (ret)
                        return ret;
                mc.precharge++;