mn10300/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 mn10300.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 25 insertions, 8 deletions

diff --git a/arch/mn10300/mm/fault.c b/arch/mn10300/mm/fault.c
index 90f346f7392d..d48a84fd7fae 100644
--- a/arch/mn10300/mm/fault.c
+++ b/arch/mn10300/mm/fault.c
@@ -123,7 +123,8 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long fault_code,
         struct mm_struct *mm;
         unsigned long page;
         siginfo_t info;
-        int write, fault;
+        int fault;
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 #ifdef CONFIG_GDBSTUB
         /* handle GDB stub causing a fault */
@@ -170,6 +171,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long fault_code,
         if (in_atomic() || !mm)
                 goto no_context;
 
+retry:
         down_read(&mm->mmap_sem);
 
         vma = find_vma(mm, address);
@@ -220,7 +222,6 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long fault_code,
  */
 good_area:
         info.si_code = SEGV_ACCERR;
-        write = 0;
         switch (fault_code & (MMUFCR_xFC_PGINVAL|MMUFCR_xFC_TYPE)) {
         default:        /* 3: write, present */
         case MMUFCR_xFC_TYPE_WRITE:
@@ -232,7 +233,7 @@ good_area:
         case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_WRITE:
                 if (!(vma->vm_flags & VM_WRITE))
                         goto bad_area;
-                write++;
+                flags |= FAULT_FLAG_WRITE;
                 break;
 
                 /* read from protected page */
@@ -251,7 +252,11 @@ good_area:
          * make sure we exit gracefully rather than endlessly redo
          * the fault.
          */
-        fault = handle_mm_fault(mm, vma, address, 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;
@@ -259,10 +264,22 @@ good_area:
                         goto do_sigbus;
                 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;