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, 4 insertions, 3 deletions

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 2dd69bf4af46..51ab9e7e6c39 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -223,9 +223,6 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
         is_write = error_code & ESR_DST;
 #endif /* CONFIG_4xx || CONFIG_BOOKE */
 
-        if (is_write)
-                flags |= FAULT_FLAG_WRITE;
-
 #ifdef CONFIG_PPC_ICSWX
         /*
          * we need to do this early because this "data storage
@@ -288,6 +285,9 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
         if (user_mode(regs))
                 store_update_sp = store_updates_sp(regs);
 
+        if (user_mode(regs))
+                flags |= FAULT_FLAG_USER;
+
         /* When running in the kernel we expect faults to occur only to
          * addresses in user space.  All other faults represent errors in the
          * kernel and should generate an OOPS.  Unfortunately, in the case of an
@@ -415,6 +415,7 @@ good_area:
         } else if (is_write) {
                 if (!(vma->vm_flags & VM_WRITE))
                         goto bad_area;
+                flags |= FAULT_FLAG_WRITE;
         /* a read */
         } else {
                 /* protection fault */