netdev - RE: SG_IO with >4k buffer size to iscsi sg device causes "Bad page" panic

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Date:	Thu, 10 May 2007 12:31:18 -0600
From:	"Qi, Yanling" <Yanling.Qi@....com>
To:	<open-iscsi@...glegroups.com>
Cc:	<netdev@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
	<linux-iscsi-devel@...ts.sourceforge.net>, <michaelc@...wisc.edu>,
	<dougg@...que.net>, <James.Bottomley@...eleye.com>
Subject: RE: SG_IO with >4k buffer size to iscsi sg device causes "Bad page" panic



> -----Original Message-----
> From: open-iscsi@...glegroups.com [mailto:open-iscsi@...glegroups.com]
On
> Behalf Of Herbert Xu
> Sent: Wednesday, May 09, 2007 6:39 PM
> To: Qi, Yanling
> Cc: netdev@...r.kernel.org; linux-scsi@...r.kernel.org; open-
> iscsi@...glegroups.com; linux-iscsi-devel@...ts.sourceforge.net; Qi,
> Yanling; michaelc@...wisc.edu; dougg@...que.net;
> James.Bottomley@...eleye.com
> Subject: Re: SG_IO with >4k buffer size to iscsi sg device causes "Bad
> page" panic
> 
> 
> Qi, Yanling <Yanling.Qi@....com> wrote:
> > @@ -2571,6 +2572,13 @@ sg_page_malloc(int rqSz, int lowDma, int
> >                resp = (char *) __get_free_pages(page_mask, order);
> > /* try half */
> >                resSz = a_size;
> >        }
> > +       tmppage = virt_to_page(resp);
> > +       for( m = PAGE_SIZE; m < resSz; m += PAGE_SIZE )
> > +       {
> > +               tmppage++;
> > +               SetPageReserved(tmppage);
> > +       }
> > +
> 
[Qi, Yanling]
If I do a get_page() at sg_page_malloc() time and then do a put_page()
at sg_page_free() time, I worry about a race condition that the page
gets re-used before calling free_pages().

Thanks,
Yanling
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