fix invalidate_inode_pages2_range() to not clear ret

DIO invalidates page cache through invalidate_inode_pages2_range().
invalidate_inode_pages2_range() sets ret=-EIO when
invalidate_complete_page2() fails, but this ret is cleared if
do_launder_page() succeed on a page of next index.

In this case, dio is carried out even if invalidate_complete_page2() fails
on some pages.

This can cause inconsistency between memory and blocks on HDD because the
page cache still exists.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Ken Chen <kenchen@google.com>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Chuck Lever <cel@citi.umich.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/truncate.c

@@ -391,6 +391,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 	pgoff_t next;
 	int i;
 	int ret = 0;
+	int ret2 = 0;
 	int did_range_unmap = 0;
 	int wrapped = 0;
 
@@ -438,9 +439,13 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
 				}
 			}
 			BUG_ON(page_mapped(page));
-			ret = do_launder_page(mapping, page);
-			if (ret == 0 && !invalidate_complete_page2(mapping, page))
-				ret = -EIO;
+			ret2 = do_launder_page(mapping, page);
+			if (ret2 == 0) {
+				if (!invalidate_complete_page2(mapping, page))
+					ret2 = -EIO;
+			}
+			if (ret2 < 0)
+				ret = ret2;
 			unlock_page(page);
 		}
 		pagevec_release(&pvec);