Btrfs: fix old data problem caused by aio vs dio

index 876cddd..fc0f485 100644
@@ -18,6 +18,7 @@
 
 #include <linux/fs.h>
 #include <linux/pagemap.h>
+#include <linux/pagevec.h>
 #include <linux/highmem.h>
 #include <linux/time.h>
 #include <linux/init.h>

@@ -1328,6 +1329,91 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
 	return num_written ? num_written : ret;
 }
 
+static void btrfs_dio_update_existed_pages(struct inode *inode,
+					   struct iov_iter *it,
+					   loff_t pos, size_t size)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct pagevec pvec;
+	pgoff_t index;
+	pgoff_t end;
+	size_t copied;
+	loff_t copy_pos = pos;
+	int offset = pos & (PAGE_CACHE_SIZE - 1);
+	int i;
+
+	BUG_ON(pos & (PAGE_CACHE_SIZE - 1));
+	BUG_ON(size & (PAGE_CACHE_SIZE - 1));
+
+	pagevec_init(&pvec, 0);
+	index = pos >> PAGE_CACHE_SHIFT;
+	end = (pos + size - 1) >> PAGE_CACHE_SHIFT;
+
+	while (index <= end && pagevec_lookup(&pvec, mapping, index,
+			min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
+		i = 0;
+		while (i < pagevec_count(&pvec)) {
+			struct page *page = pvec.pages[i];
+			size_t count = min_t(size_t, PAGE_CACHE_SIZE - offset,
+					     size);
+
+			index = page->index;
+			if (index > end)
+				break;
+
+			lock_page(page);
+			WARN_ON(page->index != index);
+			BUG_ON(PageDirty(page));
+			BUG_ON(PageWriteback(page));
+
+			if (page->mapping != mapping) {
+				unlock_page(page);
+				i++;
+				continue;
+			}
+
+			if (!PageUptodate(page)) {
+				unlock_page(page);
+				i++;
+				continue;
+			}
+
+			if ((index << PAGE_CACHE_SHIFT) > copy_pos) {
+				copied = (index << PAGE_CACHE_SHIFT) - copy_pos;
+				iov_iter_advance(it, copied);
+				offset = 0;
+				size -= copied;
+				count = min_t(size_t, PAGE_CACHE_SIZE, size);
+			}
+
+			pagefault_disable();
+			copied = iov_iter_copy_from_user_atomic(page, it,
+								offset,
+								count);
+			pagefault_enable();
+			flush_dcache_page(page);
+
+			if (copied < count)
+				copied = 0;
+
+			iov_iter_advance(it, copied);
+			size -= copied;
+			copy_pos += copied;
+
+			if (unlikely(copied < PAGE_CACHE_SIZE - offset)) {
+				offset += copied;
+			} else {
+				offset = 0;
+				i++;
+			}
+			unlock_page(page);
+		}
+		pagevec_release(&pvec);
+		cond_resched();
+		index++;
+	}
+}
+
 static ssize_t __btrfs_direct_write(struct kiocb *iocb,
 				    const struct iovec *iov,
 				    unsigned long nr_segs, loff_t pos,

@@ -1356,6 +1442,11 @@ static ssize_t __btrfs_direct_write(struct kiocb *iocb,
 		mark_inode_dirty(inode);
 	}
 
+	if (written > 0) {
+		iov_iter_init(&i, iov, nr_segs, count, 0);
+		btrfs_dio_update_existed_pages(inode, &i, pos, written);
+	}
+
 	if (written < 0 || written == count)
 		return written;
 

index 3f2c8cb..6de67a5 100644
@@ -6350,6 +6350,7 @@ static ssize_t check_direct_IO(struct btrfs_root *root, int rw, struct kiocb *io
 out:
 	return retval;
 }
+
 static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
 			const struct iovec *iov, loff_t offset,
 			unsigned long nr_segs)