ext2: call dax_pfn_mkwrite() for DAX fsync/msync

To properly support the new DAX fsync/msync infrastructure filesystems
need to call dax_pfn_mkwrite() so that DAX can track when user pages are
dirtied.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ext2/file.c

@@ -102,8 +102,8 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 {
 	struct inode *inode = file_inode(vma->vm_file);
 	struct ext2_inode_info *ei = EXT2_I(inode);
-	int ret = VM_FAULT_NOPAGE;
 	loff_t size;
+	int ret;
 
 	sb_start_pagefault(inode->i_sb);
 	file_update_time(vma->vm_file);
@@ -113,6 +113,8 @@ static int ext2_dax_pfn_mkwrite(struct vm_area_struct *vma,
 	size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	if (vmf->pgoff >= size)
 		ret = VM_FAULT_SIGBUS;
+	else
+		ret = dax_pfn_mkwrite(vma, vmf);
 
 	up_read(&ei->dax_sem);
 	sb_end_pagefault(inode->i_sb);