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, 10 insertions, 7 deletions

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 0bb7db41f4fe..6d6acf153bff 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -199,13 +199,6 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
         unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC;
         unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
-        if (esr & ESR_LNX_EXEC) {
-                vm_flags = VM_EXEC;
-        } else if ((esr & ESR_WRITE) && !(esr & ESR_CM)) {
-                vm_flags = VM_WRITE;
-                mm_flags |= FAULT_FLAG_WRITE;
-        }
-
         tsk = current;
         mm  = tsk->mm;
 
@@ -220,6 +213,16 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
         if (in_atomic() || !mm)
                 goto no_context;
 
+        if (user_mode(regs))
+                mm_flags |= FAULT_FLAG_USER;
+
+        if (esr & ESR_LNX_EXEC) {
+                vm_flags = VM_EXEC;
+        } else if ((esr & ESR_WRITE) && !(esr & ESR_CM)) {
+                vm_flags = VM_WRITE;
+                mm_flags |= FAULT_FLAG_WRITE;
+        }
+
         /*
          * As per x86, we may deadlock here. However, since the kernel only
          * validly references user space from well defined areas of the code,