[PATCH 09/20] m32r/mm/fault.c: Port OOM changes to do_page_fault

[Kautuk Consul <consul.kautuk@gmail.com>]

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 m32r.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
---
 arch/m32r/mm/fault.c |   33 ++++++++++++++++++++++++++++-----
 1 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/arch/m32r/mm/fault.c b/arch/m32r/mm/fault.c
index 2c9aeb4..cfc7e89 100644
--- a/arch/m32r/mm/fault.c
+++ b/arch/m32r/mm/fault.c
@@ -82,6 +82,7 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code,
 	int write;
 	int fault;
 	siginfo_t info;
+	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 	/*
 	 * If BPSW IE bit enable --> set PSW IE bit
@@ -137,6 +138,8 @@ asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code,
 		if ((error_code & ACE_USERMODE) == 0 &&
 		    !search_exception_tables(regs->psw))
 			goto bad_area_nosemaphore;
+
+retry:
 		down_read(&mm->mmap_sem);
 	}
 
@@ -175,6 +178,7 @@ good_area:
 			if (!(vma->vm_flags & VM_WRITE))
 				goto bad_area;
 			write++;
+			flags |= FAULT_FLAG_WRITE;
 			break;
 		case ACE_PROTECTION:	/* read, present */
 		case 0:		/* read, not present */
@@ -195,7 +199,11 @@ good_area:
 	 */
 	addr = (address & PAGE_MASK);
 	set_thread_fault_code(error_code);
-	fault = handle_mm_fault(mm, vma, addr, write ? FAULT_FLAG_WRITE : 0);
+	fault = handle_mm_fault(mm, vma, addr, 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;
@@ -203,10 +211,25 @@ good_area:
 			goto do_sigbus;
 		BUG();
 	}
-	if (fault & VM_FAULT_MAJOR)
-		tsk->maj_flt++;
-	else
-		tsk->min_flt++;
+
+	if (flags & FAULT_FLAG_ALLOW_RETRY) {
+		if (fault & VM_FAULT_MAJOR)
+			tsk->maj_flt++;
+		else
+			tsk->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;
+		}
+	}
+
 	set_thread_fault_code(0);
 	up_read(&mm->mmap_sem);
 	return;
-- 
1.7.5.4