hexagon/mm/vm_fault.c: Port OOM changes to do_page_fault

Commit d065bd810b6deb67d4897a14bfe21f8eb526ba99
(mm: retry page fault when blocking on disk transfer) and
commit 37b23e0525d393d48a7d59f870b3bc061a30ccdb
(x86,mm: make pagefault killable)

The above commits introduced changes into the x86 pagefault handler
for making the page fault handler retryable as well as killable.

These changes reduce the mmap_sem hold time, which is crucial
during OOM killer invocation.

Port these changes to hexagon.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: Richard Kuo <rkuo@codeaurora.org>

1 files changed, 17 insertions, 5 deletions

diff --git a/arch/hexagon/mm/vm_fault.c b/arch/hexagon/mm/vm_fault.c
index c10b76ff9d65..06695cc4fe58 100644
--- a/arch/hexagon/mm/vm_fault.c
+++ b/arch/hexagon/mm/vm_fault.c
@@ -53,6 +53,8 @@ void do_page_fault(unsigned long address, long cause, struct pt_regs *regs)
         int si_code = SEGV_MAPERR;
         int fault;
         const struct exception_table_entry *fixup;
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+                                 (cause > 0 ? FAULT_FLAG_WRITE : 0);
 
         /*
          * If we're in an interrupt or have no user context,
@@ -63,6 +65,7 @@ void do_page_fault(unsigned long address, long cause, struct pt_regs *regs)
 
         local_irq_enable();
 
+retry:
         down_read(&mm->mmap_sem);
         vma = find_vma(mm, address);
         if (!vma)
@@ -96,14 +99,23 @@ good_area:
                 break;
         }
 
-        fault = handle_mm_fault(mm, vma, address, (cause > 0));
+        fault = handle_mm_fault(mm, vma, address, flags);
+
+        if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+                return;
 
         /* The most common case -- we are done. */
         if (likely(!(fault & VM_FAULT_ERROR))) {
-                if (fault & VM_FAULT_MAJOR)
-                        current->maj_flt++;
-                else
-                        current->min_flt++;
+                if (flags & FAULT_FLAG_ALLOW_RETRY) {
+                        if (fault & VM_FAULT_MAJOR)
+                                current->maj_flt++;
+                        else
+                                current->min_flt++;
+                        if (fault & VM_FAULT_RETRY) {
+                                flags &= ~FAULT_FLAG_ALLOW_RETRY;
+                                goto retry;
+                        }
+                }
 
                 up_read(&mm->mmap_sem);
                 return;