consistent treatment of EFAULT on O_DIRECT read/write

Make local filesystems treat a fault as shortened IO,
returning -EFAULT only if nothing had been transferred.
That's how everything else (NFS, FUSE, ceph, Lustre)
behaves.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 7c3ce73..fb9aa16 100644 (file)
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -246,6 +246,9 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
                if ((dio->op == REQ_OP_READ) &&
                    ((offset + transferred) > dio->i_size))
                        transferred = dio->i_size - offset;
+               /* ignore EFAULT if some IO has been done */
+               if (unlikely(ret == -EFAULT) && transferred)
+                       ret = 0;
        }
 
        if (ret == 0)