linux-kernel - RE: [PATCH 1/1] Drivers: scsi: storvsc: Account for in-transit packets in the RESET path

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Message-ID: <426367E2313C2449837CD2DE46E7EAF930A2E7CA@SN2PRD0310MB382.namprd03.prod.outlook.com>
Date:	Tue, 9 Oct 2012 13:48:24 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"ohering@...e.com" <ohering@...e.com>,
	"hch@...radead.org" <hch@...radead.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH 1/1] Drivers: scsi: storvsc: Account for in-transit
 packets in the RESET path



> -----Original Message-----
> From: James Bottomley [mailto:James.Bottomley@...senPartnership.com]
> Sent: Tuesday, October 09, 2012 7:38 AM
> To: KY Srinivasan
> Cc: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org;
> devel@...uxdriverproject.org; ohering@...e.com; hch@...radead.org; linux-
> scsi@...r.kernel.org; stable@...r.kernel.org
> Subject: Re: [PATCH 1/1] Drivers: scsi: storvsc: Account for in-transit packets in
> the RESET path
> 
> On Mon, 2012-10-08 at 15:51 +0000, KY Srinivasan wrote:
> >
> > > -----Original Message-----
> > > From: K. Y. Srinivasan [mailto:kys@...rosoft.com]
> > > Sent: Tuesday, October 02, 2012 2:04 PM
> > > To: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org;
> > > devel@...uxdriverproject.org; ohering@...e.com;
> jbottomley@...allels.com;
> > > hch@...radead.org; linux-scsi@...r.kernel.org
> > > Cc: KY Srinivasan; stable@...r.kernel.org
> > > Subject: [PATCH 1/1] Drivers: scsi: storvsc: Account for in-transit packets in
> the
> > > RESET path
> > >
> > > Properly account for I/O in transit before returning from the RESET call.
> > > In the absense of this patch, we could have a situation where the host may
> > > respond to a command that was issued prior to the issuance of the RESET
> > > command at some arbitrary time after responding to the RESET command.
> > > Currently, the host does not do anything with the RESET command.
> > >
> > > Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> > > Cc: stable@...r.kernel.org
> > > ---
> > >  drivers/scsi/storvsc_drv.c |    5 +++++
> > >  1 files changed, 5 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> > > index 528d52b..0144078 100644
> > > --- a/drivers/scsi/storvsc_drv.c
> > > +++ b/drivers/scsi/storvsc_drv.c
> > > @@ -1221,7 +1221,12 @@ static int storvsc_host_reset_handler(struct
> scsi_cmnd
> > > *scmnd)
> > >  	/*
> > >  	 * At this point, all outstanding requests in the adapter
> > >  	 * should have been flushed out and return to us
> > > +	 * There is a potential race here where the host may be in
> > > +	 * the process of responding when we return from here.
> > > +	 * Just wait for all in-transit packets to be accounted for
> > > +	 * before we return from here.
> > >  	 */
> > > +	storvsc_wait_to_drain(stor_device);
> > >
> > >  	return SUCCESS;
> > >  }
> > > --
> > > 1.7.4.1
> >
> > James,
> >
> > This patch is critical for running Linux based workloads on our Cloud
> infrastructure - Azure.
> > Please let me know if there are any issues.
> 
> So just for next time: it's a bit hard to work out this is a critical
> issue from the change log.  If I had to guess, I'd say the response to a
> command killed by reset causes some type of use after free and a
> potential oops (all of which would have been very nice in the change
> log)?

You guessed right! My apologies, I will add such details in the change log
in the future.

Regards,

K. Y
> 
> James
> 
> 
> 
>