[Qemu-devel] [PATCH 3/3] qemu-nbd: Improve error reporting

[Ryota Ozaki]

- use err(3) instead of errx(3) if errno is available
  to report why failed
- let fail prior to daemon(3) if opening a nbd file
  is likely to fail after daemonizing to avoid silent
  failure exit
- add missing 'ret = 1' when unix_socket_outgoing failed

Signed-off-by: Ryota Ozaki <ozaki.ry...@gmail.com>
---
 qemu-nbd.c |   17 ++++++++++++-----
 1 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/qemu-nbd.c b/qemu-nbd.c
index 7ef409f..d3e1814 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -324,7 +324,7 @@ int main(int argc, char **argv)
     if (disconnect) {
         fd = open(argv[optind], readonly ? O_RDONLY : O_RDWR);
         if (fd == -1) {
-            errx(EXIT_FAILURE, "Cannot open %s", argv[optind]);
+            err(EXIT_FAILURE, "Cannot open %s", argv[optind]);
         }
 
         nbd_disconnect(fd);
@@ -343,25 +343,31 @@ int main(int argc, char **argv)
         return 1;
     }
 
-    if (bdrv_open(bs, argv[optind], flags) < 0) {
-        return 1;
+    if ((ret = bdrv_open(bs, argv[optind], flags)) < 0) {
+        errno = -ret;
+        err(EXIT_FAILURE, "Failed to bdrv_open '%s'", argv[optind]);
     }
 
     fd_size = bs->total_sectors * 512;
 
     if (partition != -1 &&
         find_partition(bs, partition, &dev_offset, &fd_size)) {
-        errx(EXIT_FAILURE, "Could not find partition %d", partition);
+        err(EXIT_FAILURE, "Could not find partition %d", partition);
     }
 
     if (device) {
         pid_t pid;
         int sock;
 
+        /* want to fail before daemonizing */
+        if (access(device, readonly ? R_OK : R_OK|W_OK) == -1) {
+            err(EXIT_FAILURE, "Could not access '%s'", device);
+        }
+
         if (!verbose) {
             /* detach client and server */
             if (daemon(0, 0) == -1) {
-                errx(EXIT_FAILURE, "Failed to daemonize");
+                err(EXIT_FAILURE, "Failed to daemonize");
             }
         }
 
@@ -386,6 +392,7 @@ int main(int argc, char **argv)
                 sock = unix_socket_outgoing(socket);
                 if (sock == -1) {
                     if (errno != ENOENT && errno != ECONNREFUSED) {
+                        ret = 1;
                         goto out;
                     }
                     sleep(1);  /* wait children */
-- 
1.6.5.2