svn commit: r340187 - head/sys/geom

[Maxim Sobolev]

Rodney, this was actually my original intention, however then I noticed in
the GEOM code there is at least one case when BIO_FLUSH request is being
generated internally with bio_offset == mediasize and bio_lenth == 0, so I
thought there might be some need to allow such requests through. But I'd
happily go with the stricter rule if it does no harm. I simply don't know
enough about the intended use and the logic behind zero-length transfers to
make that call.

-Max

int
g_io_flush(struct g_consumer *cp)
{
...
        bp = g_alloc_bio();
        bp->bio_cmd = BIO_FLUSH;
...
        bp->bio_offset = cp->provider->mediasize;
        bp->bio_length = 0;
        bp->bio_data = NULL;
        g_io_request(bp, cp);
 ...
}



On Tue, Nov 6, 2018 at 8:31 AM Rodney W. Grimes <
freebsd at pdx.rh.cn85.dnsmgr.net> wrote:
>
> > Author: sobomax
> > Date: Tue Nov  6 15:55:41 2018
> > New Revision: 340187
> > URL: https://svnweb.freebsd.org/changeset/base/340187
> >
> > Log:
> >   Don't allow BIO_READ, BIO_WRITE or BIO_DELETE requests that are
> >   fully beyond the end of providers media. The only exception is made
> >   for the zero length transfers which are allowed to be just on the
> >   boundary. Previously, any requests starting on the boundary (i.e. next
> >   byte after the last one) have been allowed to go through.
> >
> >   No response from:   freebsd-geom@, phk
> >   MFC after:          1 month
> >
> > Modified:
> >   head/sys/geom/geom_io.c
> >
> > Modified: head/sys/geom/geom_io.c
> >
==============================================================================
> > --- head/sys/geom/geom_io.c   Tue Nov  6 15:52:49 2018        (r340186)
> > +++ head/sys/geom/geom_io.c   Tue Nov  6 15:55:41 2018        (r340187)
> > @@ -420,6 +420,8 @@ g_io_check(struct bio *bp)
> >                       return (EIO);
> >               if (bp->bio_offset > pp->mediasize)
> >                       return (EIO);
> > +             if (bp->bio_offset == pp->mediasize && bp->bio_length > 0)
> > +                     return (EIO);
>
> Isnt mediasize 0 based, such that any operation at pp->mediasize is
> technically past the end of the media and should get an EIO no
> matter how big it is?
>
> Who is doing 0 byte operations at pp->mediasize?
> That code should probably be fixed rather than allowing
> this special case here.
>
> >               /* Truncate requests to the end of providers media. */
> >               excess = bp->bio_offset + bp->bio_length;
> >
> >
>
> --
> Rod Grimes
rgrimes at freebsd.org