From acddd932feabcb57abfa6416f7ff68912e8b449a Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <djwong@us.ibm.com>
Date: Wed, 18 May 2011 13:55:20 -0400
Subject: [PATCH] --- yaml --- r: 251734 b: refs/heads/master c:
 0e499890c1fd9e0a1bed02002161c4c7873d7489 h: refs/heads/master v: v3

---
 [refs]                |  2 +-
 trunk/fs/ext4/inode.c | 24 +++++++++++++++++++-----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/[refs] b/[refs]
index 330d122311ea..b27e2ce3c2d5 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7cb1a5351da8ac499d965a78e94c79ad27891f43
+refs/heads/master: 0e499890c1fd9e0a1bed02002161c4c7873d7489
diff --git a/trunk/fs/ext4/inode.c b/trunk/fs/ext4/inode.c
index f6caaac83731..6348c1f610c2 100644
--- a/trunk/fs/ext4/inode.c
+++ b/trunk/fs/ext4/inode.c
@@ -5809,15 +5809,19 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 		goto out_unlock;
 	}
 	ret = 0;
-	if (PageMappedToDisk(page))
-		goto out_unlock;
+
+	lock_page(page);
+	wait_on_page_writeback(page);
+	if (PageMappedToDisk(page)) {
+		up_read(&inode->i_alloc_sem);
+		return VM_FAULT_LOCKED;
+	}
 
 	if (page->index == size >> PAGE_CACHE_SHIFT)
 		len = size & ~PAGE_CACHE_MASK;
 	else
 		len = PAGE_CACHE_SIZE;
 
-	lock_page(page);
 	/*
 	 * return if we have all the buffers mapped. This avoid
 	 * the need to call write_begin/write_end which does a
@@ -5827,8 +5831,8 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	if (page_has_buffers(page)) {
 		if (!walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
 					ext4_bh_unmapped)) {
-			unlock_page(page);
-			goto out_unlock;
+			up_read(&inode->i_alloc_sem);
+			return VM_FAULT_LOCKED;
 		}
 	}
 	unlock_page(page);
@@ -5848,6 +5852,16 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	if (ret < 0)
 		goto out_unlock;
 	ret = 0;
+
+	/*
+	 * write_begin/end might have created a dirty page and someone
+	 * could wander in and start the IO.  Make sure that hasn't
+	 * happened.
+	 */
+	lock_page(page);
+	wait_on_page_writeback(page);
+	up_read(&inode->i_alloc_sem);
+	return VM_FAULT_LOCKED;
 out_unlock:
 	if (ret)
 		ret = VM_FAULT_SIGBUS;