On Sat, 20 Mar 2010, Ryota Ozaki wrote:
> - 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
I'm under impression that you and the original author of this
code is misunderstading how err[x] works, first argument is
what will be used to exit the process and has little to do
with POSIX/C error codes.
> ---
> qemu-nbd.c | 16 +++++++++++-----
> 1 files changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index b89c361..5f10ff0 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -316,7 +316,7 @@ int main(int argc, char **argv)
> if (disconnect) {
> fd = open(argv[optind], O_RDWR);
> if (fd == -1)
> - errx(errno, "Cannot open %s", argv[optind]);
> + err(errno, "Cannot open %s", argv[optind]);
>
> nbd_disconnect(fd);
>
> @@ -333,23 +333,29 @@ int main(int argc, char **argv)
> if (bs == NULL)
> return 1;
>
> - if (bdrv_open(bs, argv[optind], flags) < 0)
> - return 1;
> + if ((ret = bdrv_open(bs, argv[optind], flags)) < 0) {
> + errno = -ret;
> + err(errno, "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(errno, "Could not find partition %d", partition);
> + err(errno, "Could not find partition %d", partition);
>
> if (device) {
> pid_t pid;
> int sock;
>
> + /* want to fail before daemonizing */
> + if (access(device, R_OK|W_OK) == -1)
> + err(errno, "Could not access '%s'", device);
> +
> if (!verbose) {
> /* detach client and server */
> if (daemon(0, 0) == -1) {
> - errx(errno, "Failed to daemonize");
> + err(errno, "Failed to daemonize");
> }
> }
>
>
--
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