Btrfs: mark mapping with error flag to report errors to userspace

commit 5dca6eea91653e9949ce6eb9e9acab6277e2f2c4 upstream.

According to commit 865ffef3
(fs: fix fsync() error reporting),
it's not stable to just check error pages because pages can be
truncated or invalidated, we should also mark mapping with error
flag so that a later fsync can catch the error.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>