Re: [Libguestfs] [PATCH] file: Better support for read-only files

>> >> h->fd = openat (dfd, file, flags); >> + if (h->fd == -1 && !readonly) { >> + int saved_errno = errno; >> + flags = (flags & ~O_ACCMODE) | O_RDONLY; >> + h->fd = openat (dfd, file, flags); >> + if (h->fd == -1) >> + errno = saved_errno; >> + else >> + h->can_write = false; >> + } >> if (h->fd == -1) { >> nbdkit_error ("open: %s: %m", file); > > This will always report the error that failed open when using O_RDWR. > But if open(O_RDWR) fail with EPERM, and open(O_RDONLY) fails > with another error, the other error will be hidden. > > Maybe it is better to log the first error so we don't need to save errno > when trying to open in read only mode? Maybe we could put it in a nbdkit_debug message?