arch: mm: pass userspace fault flag to generic fault handler

Unlike global OOM handling, memory cgroup code will invoke the OOM killer
in any OOM situation because it has no way of telling faults occuring in
kernel context - which could be handled more gracefully - from
user-triggered faults.

Pass a flag that identifies faults originating in user space from the
architecture-specific fault handlers to generic code so that memcg OOM
handling can be improved.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: azurIt <azurit@pobox.sk>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 7de4469915f0..fc6679210d83 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -302,6 +302,8 @@ static inline int do_exception(struct pt_regs *regs, int access)
         address = trans_exc_code & __FAIL_ADDR_MASK;
         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
         flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+        if (user_mode(regs))
+                flags |= FAULT_FLAG_USER;
         if (access == VM_WRITE || (trans_exc_code & store_indication) == 0x400)
                 flags |= FAULT_FLAG_WRITE;
         down_read(&mm->mmap_sem);