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From: Steven Stewart-Gallus <sstewartgallus00@mylangara.bc.ca>
To: Andy Lutomirski <luto@amacapital.net>
Cc: linux-kernel@vger.kernel.org
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Date: Thu, 04 Sep 2014 07:35:08 +0000 (GMT)
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Subject: Re: How is pivot_root intended to be used?
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Thank you, I think I will change the code to be like:

    int old_root = open("/", O_DIRECTORY);
    if (-1 == old_root) {
        perror("open");
        return EXIT_FAILURE;
    }

    if (-1 == syscall(__NR_pivot_root, ".", ".")) {
        perror("pivot_root");
        return EXIT_FAILURE;
    }

    if (-1 == fchdir(old_root)) {
        perror("fchdir");
        return EXIT_FAILURE;
    }

    if (-1 == umount2(".", MNT_DETACH)) {
        perror("umount");
        return EXIT_FAILURE;
    }

    if (-1 == close(old_root)) {
        perror("close");
        return EXIT_FAILURE;
    }

    if (-1 == chdir("/")) {
        perror("chdir");
        return EXIT_FAILURE;
    }

This seems more understandable to me and less likely to have bugs later on.