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, 2 deletions

diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
index 94d3a31ab144..becc42bb1849 100644
--- a/arch/mips/mm/fault.c
+++ b/arch/mips/mm/fault.c
@@ -42,8 +42,7 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
         const int field = sizeof(unsigned long) * 2;
         siginfo_t info;
         int fault;
-        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
-                                                 (write ? FAULT_FLAG_WRITE : 0);
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 #if 0
         printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(),
@@ -93,6 +92,8 @@ static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
         if (in_atomic() || !mm)
                 goto bad_area_nosemaphore;
 
+        if (user_mode(regs))
+                flags |= FAULT_FLAG_USER;
 retry:
         down_read(&mm->mmap_sem);
         vma = find_vma(mm, address);
@@ -114,6 +115,7 @@ good_area:
         if (write) {
                 if (!(vma->vm_flags & VM_WRITE))
                         goto bad_area;
+                flags |= FAULT_FLAG_WRITE;
         } else {
                 if (cpu_has_rixi) {
                         if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {