Date: Tue, 6 Nov 2018 08:54:10 -0800 From: Maxim Sobolev <sobomax@freebsd.org> To: rgrimes@freebsd.org Cc: src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r340187 - head/sys/geom Message-ID: <CAH7qZfvW2ZEqWL5yg9i67=zD562-KtY3tgcpSzCjku1JT3HGXQ@mail.gmail.com> In-Reply-To: <201811061630.wA6GUwaK096771@pdx.rh.CN85.dnsmgr.net> References: <201811061555.wA6FtfiT017783@repo.freebsd.org> <201811061630.wA6GUwaK096771@pdx.rh.CN85.dnsmgr.net>
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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@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@freebsd.org
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