9pfs: fix filesystem to wait for stable page writeback

Fix up the ->page_mkwrite handler to provide stable page writes if necessary.

Signed-off-by: Darrick J. Wong <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Artem Bityutskiy <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Steven Whitehouse <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Eric Van Hensbergen <[email protected]>
Cc: Ron Minnich <[email protected]>
Cc: Latchesar Ionkov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/9p/vfs_file.c

@@ -616,6 +616,7 @@ v9fs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 	lock_page(page);
 	if (page->mapping != inode->i_mapping)
 		goto out_unlock;
+	wait_for_stable_page(page);
 
 	return VM_FAULT_LOCKED;
 out_unlock: