parisc/mm/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 parisc.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 25 insertions, 5 deletions

diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index 18162ce4261e..f247a3480e8e 100644
--- a/arch/parisc/mm/fault.c
+++ b/arch/parisc/mm/fault.c
@@ -175,10 +175,12 @@ void do_page_fault(struct pt_regs *regs, unsigned long code,
         struct mm_struct *mm = tsk->mm;
         unsigned long acc_type;
         int fault;
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
         if (in_atomic() || !mm)
                 goto no_context;
 
+retry:
         down_read(&mm->mmap_sem);
         vma = find_vma_prev(mm, address, &prev_vma);
         if (!vma || address < vma->vm_start)
@@ -201,7 +203,12 @@ good_area:
          * fault.
          */
 
-        fault = handle_mm_fault(mm, vma, address, (acc_type & VM_WRITE) ? FAULT_FLAG_WRITE : 0);
+        fault = handle_mm_fault(mm, vma, address,
+                        flags | ((acc_type & VM_WRITE) ? FAULT_FLAG_WRITE : 0));
+
+        if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+                return;
+
         if (unlikely(fault & VM_FAULT_ERROR)) {
                 /*
                  * We hit a shared mapping outside of the file, or some
@@ -214,10 +221,23 @@ good_area:
                         goto bad_area;
                 BUG();
         }
-        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;
+
+                        /*
+                         * No need to up_read(&mm->mmap_sem) as we would
+                         * have already released it in __lock_page_or_retry
+                         * in mm/filemap.c.
+                         */
+
+                        goto retry;
+                }
+        }
         up_read(&mm->mmap_sem);
         return;