btrfs-progs: send-stream: handle EINTR during buffer reads

Read error are handled but EINTR is a transient and can be handled
without returning a hard error.

Signed-off-by: David Sterba <dsterba@suse.com>

Author: kdave

common/send-stream.c

@@ -76,6 +76,8 @@ static int read_buf(struct btrfs_send_stream *sctx, char *buf, size_t len)
 
 		rbytes = read(sctx->fd, buf + pos, len - pos);
 		if (rbytes < 0) {
+			if (errno == EINTR)
+				continue;
 			ret = -errno;
 			error("read from stream failed: %m");
 			goto out;