microblaze: 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 microblaze.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>

1 files changed, 28 insertions, 5 deletions

diff --git a/arch/microblaze/mm/fault.c b/arch/microblaze/mm/fault.c
index c38a265846de..eb365d6795fa 100644
--- a/arch/microblaze/mm/fault.c
+++ b/arch/microblaze/mm/fault.c
@@ -92,6 +92,8 @@ void do_page_fault(struct pt_regs *regs, unsigned long address,
         int code = SEGV_MAPERR;
         int is_write = error_code & ESR_S;
         int fault;
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+                                         (is_write ? FAULT_FLAG_WRITE : 0);
 
         regs->ear = address;
         regs->esr = error_code;
@@ -138,6 +140,7 @@ void do_page_fault(struct pt_regs *regs, unsigned long address,
                 if (kernel_mode(regs) && !search_exception_tables(regs->pc))
                         goto bad_area_nosemaphore;
 
+retry:
                 down_read(&mm->mmap_sem);
         }
 
@@ -210,7 +213,11 @@ good_area:
          * make sure we exit gracefully rather than endlessly redo
          * the fault.
          */
-        fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
+        fault = handle_mm_fault(mm, vma, address, flags);
+
+        if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+                return;
+
         if (unlikely(fault & VM_FAULT_ERROR)) {
                 if (fault & VM_FAULT_OOM)
                         goto out_of_memory;
@@ -218,11 +225,27 @@ good_area:
                         goto do_sigbus;
                 BUG();
         }
-        if (unlikely(fault & VM_FAULT_MAJOR))
-                current->maj_flt++;
-        else
-                current->min_flt++;
+
+        if (flags & FAULT_FLAG_ALLOW_RETRY) {
+                if (unlikely(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);
+
         /*
          * keep track of tlb+htab misses that are good addrs but
          * just need pte's created via handle_mm_fault()