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<== Date ==> <== Thread ==>

Subject: Re: sscan/ saveData problem with RW permission, and not an NFS issue
From: Tim Mooney <mooney@aps.anl.gov>
To: Vesna Samardzic-Boban <Vesna.Samardzic-Boban@synchrotron.org.au>
Cc: tech-talk@aps.anl.gov
Date: Wed, 17 Apr 2013 10:36:27 -0500 (CDT)
Hi Vesna,

If it were a bug in creat(), I'd expect the same behavior here with vxWorks
6.9, but Ron Sluiter verified that it works here.  Of course it may be that
your 6.9 is differently configured.  If so, saveData's sensitivity to the
difference might be good information to have, as more folks start using
vxWorks 6.x.

I'm concerned that there is something different about your system that might
have hard-to-diagnose consequences later, and I think we should turn over a
few more stones before just moving on.  I think open(..., O_CREAT, ...) is
not exactly the same as creat().  It would succeed if the file already
existed - perhaps because saveData lacks the ability to delete files - so it's
not a bulletproof indicator that saveData can create a new file.

Are you confident that you're using NFS?  vxWorks is pretty sneaky about
silently falling back to netDrv if an NFS mount to the path it needs is not
available.  But saveData is not tested with netDrv.  On vxWorks, saveData only
works reliably with NFS.

If you are using NFS, which version are you using?

Tim

----- Original Message -----
> From: "Vesna Samardzic-Boban" <Vesna.Samardzic-Boban@synchrotron.org.au>
> To: "Tim Mooney" <mooney@aps.anl.gov>, "Andrew Johnson" <anj@aps.anl.gov>
> Cc: tech-talk@aps.anl.gov
> Sent: Wednesday, April 17, 2013 4:56:27 AM
> Subject: RE: sscan/ saveData problem with RW permission, and not an NFS issue
> 
> Hi Tim and Andrew,
> 
> Agree with Andrew it is a vxWorks bug in creat().
> But it's easier (for me) to replace the line/creat() in saveData.c
>     file= creat(tmpfile, O_RDWR);
> with open() e.g.
> #ifdef vxWorks
>     file = open (tmpfile, O_CREAT | O_RDWR, 0666);
> #else
>     file = creat (tmpfile, O_RDWR);       /* if this is needed by
>     other OS's*/
> #endif
> That way we do not depend on Wind River and their bug/fix.
> 
> REgards Vesna
> 
> ________________________________________
> From: Andrew Johnson [anj@aps.anl.gov]
> Sent: Wednesday, 17 April 2013 1:31 AM
> To: tech-talk@aps.anl.gov
> Cc: Tim Mooney; Vesna Samardzic-Boban
> Subject: Re: sscan/ saveData problem with RW permission, and not an
> NFS issue
> 
> Hi Tim,
> 
> On 2013-04-16 Tim Mooney wrote:
> > Thanks for the information.  I haven't tested sscan on vxWorks 6.9,
> > though
> > I'm told it works on vxWorks 6.8.  I don't think creat() uses
> > O_RDRW as a
> > file-permission mask, and I don't understand why open() would work
> > while
> > creat() does not.  I'm ok with making this change, but I'd like to
> > understand it better first.
> 
> I don't think there's going to be any difference in the behavior
> between
> VxWorks 6.8 and 6.9.  This is one of those things that I believe Wind
> River
> got wrong very early in the life of VxWorks and it has never been
> fixed
> properly.  This is from the documentation for creat():
>     The parameter mode is set to O_RDONLY (0), O_WRONLY (1), or
>     O_RDWR (2)
>     for the duration of time the file is open. On NFS and POSIX
>     compliant
>     file systems such as HRFS, mode refers instead to the UNIX style
>     file
>     permission bits.
> They even say that the second argument has a different meaning on
> different
> file-systems, which means there is /no/ way to write code using this
> routine
> that works properly on all file-systems, because you have to know
> what kind of
> file-system it is to give the right parameter.
> I recommend that creat() not be used in code that runs on vxWorks,
> and that
> all calls to it be replaced with the equivalent open() call instead.
>  The
> Linux man-page for creat() says:
>     creat() is equivalent to open() with flags equal to
>     O_CREAT|O_WRONLY|O_TRUNC.
> You will also need to add the mode parameter 0666.
> - Andrew
> --
> It is difficult to get a man to understand something, when his salary
> depends upon his not understanding it. -- Upton Sinclair
> 
> ________________________________________
> From: Tim Mooney [mooney@aps.anl.gov]
> Sent: Wednesday, 17 April 2013 1:18 AM
> To: Vesna Samardzic-Boban
> Cc: tech-talk@aps.anl.gov
> Subject: Re: sscan/ saveData problem with RW permission, and not an
> NFS issue
> 
> Hi Vesna,
> 
> Thanks for the information.  I haven't tested sscan on vxWorks 6.9,
> though
> I'm told it works on vxWorks 6.8.  I don't think creat() uses O_RDRW
> as a
> file-permission mask, and I don't understand why open() would work
> while
> creat() does not.  I'm ok with making this change, but I'd like to
> understand
> it better first.
> 
> Tim
> 
> ----- Original Message -----
> > From: "Vesna Samardzic-Boban"
> > <Vesna.Samardzic-Boban@synchrotron.org.au>
> > To: tech-talk@aps.anl.gov
> > Sent: Monday, April 15, 2013 8:52:30 PM
> > Subject: sscan/ saveData problem with RW permission, and not an NFS
> > issue
> >
> > Hi All,
> >
> >
> > Found a problem as follows:
> >
> > Running a scan record on a vxWorks IOC and when entering 'File
> > system' in scan_saveData.adl screen, an error message in the 'Save
> > status' field follows:
> > "RW permission denied !!!"
> >
> > At first I suspected NFS but after checking it found that my
> > problem
> > was in the sscan's saveData.c and/or VxWorks is 6.9
> >
> > Tried two versions of sscan, 2-6-6 and 2-8-2, they gave the same
> > result as above. These two versions are same regarding the
> > saveData.c and its function
> >     checkRWpermission(char* path)
> > and specifically the line
> >
> >     file= creat(tmpfile, O_RDWR);
> >
> > that creates test file "rix_" with file permissions 002 (because
> > O_RDRW = 2)
> > (O_RDRW is flag "Open for reading and writing" or File Access
> > Options)
> >
> > The file permissions 002 become
> > -------w-  in   terms of    rwxrwxrwx
> > and hence the error "RW permission denied !!!"
> >
> > Found a solution by using vxWorks function open() instead of
> > creat().
> > open() - opens a file and optionally creates a file if it does not
> > exist.
> > open() - also offers a parameter for "mode" i.e. file permissions,
> > which i set to 0x666 in the example below
> >
> >      file = open (tmpfile, O_CREAT | O_RDWR, 0666);
> >
> > Then scan data can be saved as expected.
> >
> > BTW
> > saveData.c uses open() for creating 'subdirectory'.
> >           fd = open (local_pathname, O_RDWR | O_CREAT,
> >                            FSTAT_DIR | DEFAULT_DIR_PERM | 0775);
> >
> >
> > Has anyone had similar problems ?
> > Is this an sscan/saveData.c issue or vxWorks 6.9 issue (I do not
> > have
> > any other version of vxWorks) ?
> > How about sscan/saveData on OS's other than vxWorks?
> >
> >
> > Thanks Vesna
> >
> > P.S.
> > In my vxWorks 6.9 and its ioLib.c, creat() does not offer file
> > permissions (set to 0 as below):
> > int creat
> >     (
> >     const char *name,           /* name of the file to create */
> >     int         flag            /* file permissions */
> >     )
> >     {
> >     return (ioCreateOrOpen (name, flag, 0, TRUE));
> >     }
> 
> SUPPLIERS: As of 1 January 2013, the Australian Synchrotron Company
> Ltd has changed its business name. However, the trading name will
> remain Australian Synchrotron.
> Please address all quotations and invoices to: Synchrotron Light
> Source Australia Pty Ltd (SLSA), ABN: 18 159 468 256
> 

Replies:
Re: sscan/ saveData problem with RW permission, and not an NFS issue Ron Sluiter
References:
RE: sscan/ saveData problem with RW permission, and not an NFS issue Vesna Samardzic-Boban

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