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>

diff --git a/arch/hexagon/mm/vm_fault.c b/arch/hexagon/mm/vm_fault.c
index c10b76f..06695cc 100644 (file)
--- 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;