linux-kernel - [PATCH 17/19 v2] parisc/mm/fault.c: Port OOM changes to do_page

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Message-Id: <1333195588-5490-1-git-send-email-consul.kautuk@gmail.com>
Date:	Sat, 31 Mar 2012 08:06:28 -0400
From:	Kautuk Consul <consul.kautuk@...il.com>
To:	<jejb@...isc-linux.org>, Helge Deller <deller@....de>
Cc:	linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Kautuk Consul <consul.kautuk@...il.com>
Subject: [PATCH 17/19 v2] 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.

Signed-off-by: Kautuk Consul <consul.kautuk@...il.com>
---
 arch/parisc/mm/fault.c |   29 ++++++++++++++++++++++++-----
 1 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
index 18162ce..bd66ed6 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 +221,22 @@ 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;
 
-- 
1.7.5.4

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