On 02/02/2014 08:15 PM, "Kai Mäkisara (Kolumbus)" wrote: > > On 2.2.2014, at 13.42, Hannes Reinecke <h...@suse.de> wrote: > > [part of explanation snipped from reply] > >> But we're now trying to deprecate the original (and unmaintained) >> scsi_id program and replace it with the standard 'sg_inq' program. >> Which is a standard program which just issues the respective SCSI >> command; most of the post-processing will be done by udev rules. >> And implementing the same workaround here is really a bit hackish. >> Hence this proposal to allow 'sg_inq' (or any program from sg3_utils) >> to be called without interrupting normal operations on a tape device. >> > OK. After your explanation I think adding the new MTIOCTOP operation is the > least ugly solution :-) > Ok.
>>> If you absolutely have to do this, then do it. But new ioctls are >>> deprecated and >>> also it is a bad habit to change the kernel to make things easier for a >>> single >>> program. >>> >> Well, the actual problem here is that the 'st' driver is not designed for >> multi-initiator environments. The original design for the driver assumed >> that a single program had control over the 'st' driver, and there is only >> one instance talking to the hardware. >> Which simply doesn't fit well with the modern, asynchronous, setup. >> > The basic problem is that a sequential access device does not fit well the > asynchronous setup. I admit that some simplifications have been made because of this. > >> And it's not just udev which suffers here; try to setup multipath on a tape >> device ... >> >>>> I'll be drafting up a patch. >>>> >>> If you do, don’t forget to update the documentation. >>> >> Okay. New patch attached. >> > I think you have not compiled the patched st.c: > > @@ -2263,6 +2265,8 @@ static int st_set_options(struct scsi_tape *STp, long > options) > STm->sysv = value; > if ((options & MT_ST_SILI) != 0) > STp->sili = value; > + if (value && (options & MT_ST_NOREWIND) != 0) > + Stp->rew_at_close = 0; > ^^^ > Should be STp. > > However, looking at the code already suggests that this operation does not > belong to MT_ST_*. > These bits set/clear options that persist. The operations you need is transient so that the > effect disappears when the device is closed. I think it would be better to define it as and > ordinary MTIOCTOP operation code, e.g., in mtio.h: > > #define MTNOAUTOREWIND 36 /* suppress possible pending automatic rewind */ > > or something like that? > Ok, can do. Let's draft up a new version. Cheers, Hannes -- Dr. Hannes Reinecke zSeries & Storage h...@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
