Re: [PATCH 1/2] Add a method to determine whether a block device is read-only.

[David Cantrell <dcantrell@xxxxxxxxxx>]

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On Wed, 22 Jul 2009, Chris Lumens wrote:

> ---
> isys/isys.c  |   24 ++++++++++++++++++++++++
> isys/isys.py |    6 ++++++
> 2 files changed, 30 insertions(+), 0 deletions(-)
>
> diff --git a/isys/isys.c b/isys/isys.c
> index fcec6fd..90a697c 100644
> --- a/isys/isys.c
> +++ b/isys/isys.c
> @@ -124,6 +124,7 @@ static PyObject * doGetBiosDisk(PyObject * s, PyObject * args);
> static PyObject * doSegvHandler(PyObject *s, PyObject *args);
> static PyObject * doAuditDaemon(PyObject *s);
> static PyObject * doPrefixToNetmask(PyObject *s, PyObject *args);
> +static PyObject * doDeviceReadOnly(PyObject *s, PyObject *args);
>
> static PyMethodDef isysModuleMethods[] = {
>     { "ejectcdrom", (PyCFunction) doEjectCdrom, METH_VARARGS, NULL },
> @@ -180,6 +181,7 @@ static PyMethodDef isysModuleMethods[] = {
>     { "handleSegv", (PyCFunction) doSegvHandler, METH_VARARGS, NULL },
>     { "auditdaemon", (PyCFunction) doAuditDaemon, METH_NOARGS, NULL },
>     { "prefix2netmask", (PyCFunction) doPrefixToNetmask, METH_VARARGS, NULL },
> +    { "deviceIsReadOnly", (PyCFunction) doDeviceReadOnly, METH_VARARGS, NULL },
>     { NULL, NULL, 0, NULL }
> } ;
>
> @@ -1416,4 +1418,26 @@ static PyObject * doAuditDaemon(PyObject *s) {
>     return Py_None;
> }
>
> +static PyObject * doDeviceReadOnly(PyObject *s, PyObject *args) {
> +    char *diskname = NULL;
> +    int fd, is_ro;
> +
> +    if (!PyArg_ParseTuple(args, "s", &diskname)) return NULL;
> +
> +    fd = open(diskname, O_RDONLY);
> +    if (fd == -1) {
> +      Py_INCREF(Py_None);
> +      return Py_None;
> +    }
> +
> +    if (ioctl(fd, BLKROGET, &is_ro)) {
> +        close(fd);
> +        PyErr_SetFromErrno(PyExc_SystemError);
> +        return NULL;
> +    }
> +
> +    close(fd);
> +    return PyBool_FromLong(is_ro);
> +}

Rather than PyBool_FromLong(is_ro), I would do this:

    if (is_ro)
        Py_RETURN_TRUE;
    else
        Py_RETURN_FALSE;

When we worked on pyparted, I remember the *_FromLong convenience functions
misbehaving on some 64-bit platforms.

> +
> /* vim:set shiftwidth=4 softtabstop=4: */
> diff --git a/isys/isys.py b/isys/isys.py
> index 4063130..189a6c1 100644
> --- a/isys/isys.py
> +++ b/isys/isys.py
> @@ -804,6 +804,12 @@ def driveUsesModule(device, modules):
>                     pass
>     return rc
>
> +def deviceIsReadOnly(device):
> +    if not device.startswith("/dev/"):
> +        return _isys.deviceIsReadOnly("/dev/" + device)
> +    else:
> +        return _isys.deviceIsReadOnly(device)
> +
> def mediaPresent(device):
>     try:
>         fd = os.open("/dev/%s" % device, os.O_RDONLY)

- -- 
David Cantrell <dcantrell@xxxxxxxxxx>
Red Hat / Honolulu, HI

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