Re: [PATCH-v2 1/2] mpt3sas: Refcount sas_device objects and fix unsafe list usage

[Nicholas A. Bellinger]

On Wed, 2015-09-09 at 19:59 +0530, Chaitra Basappa wrote:
> From: Sreekanth Reddy [mailto:sreekanth.reddy@xxxxxxxxxxxxx]
> Sent: Tuesday, September 08, 2015 5:26 PM
> To: Nicholas A. Bellinger
> Cc: linux-scsi; linux-kernel; James Bottomley; Calvin Owens; Christoph
> Hellwig; MPT-FusionLinux.pdl; kernel-team; Nicholas Bellinger; Chaitra
> Basappa
> Subject: Re: [PATCH-v2 1/2] mpt3sas: Refcount sas_device objects and fix
> unsafe list usage
> 
> On Sun, Aug 30, 2015 at 1:24 PM, Nicholas A. Bellinger <nab@xxxxxxxxxxxxx>
> wrote:
> > From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> >
> > These objects can be referenced concurrently throughout the driver, we
> > need a way to make sure threads can't delete them out from under each
> > other. This patch adds the refcount, and refactors the code to use it.
> >
> > Additionally, we cannot iterate over the sas_device_list without
> > holding the lock, or we risk corrupting random memory if items are
> > added or deleted as we iterate. This patch refactors
> > _scsih_probe_sas() to use the sas_device_list in a safe way.
> >
> > This patch is a port of Calvin's PATCH-v4 for mpt2sas code, atop
> > mpt3sas changes in scsi.git/for-next.
> >
> > Cc: Calvin Owens <calvinowens@xxxxxx>
> > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> > Cc: Sreekanth Reddy <sreekanth.reddy@xxxxxxxxxxxxx>
> > Cc: MPT-FusionLinux.pdl <MPT-FusionLinux.pdl@xxxxxxxxxxxxx>
> > Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> > ---
> >  drivers/scsi/mpt3sas/mpt3sas_base.h      |  25 +-
> >  drivers/scsi/mpt3sas/mpt3sas_scsih.c     | 479
> > +++++++++++++++++++++----------
> >  drivers/scsi/mpt3sas/mpt3sas_transport.c |  18 +-
> >  3 files changed, 364 insertions(+), 158 deletions(-)
> >
> > @@ -2763,7 +2874,7 @@ _scsih_block_io_device(struct MPT3SAS_ADAPTER *ioc,
> > u16 handle)
> >         struct scsi_device *sdev;
> >         struct _sas_device *sas_device;
> >
> 
> [Sreekanth] Here sas_device_lock spin lock needs to be acquired before
> calling
>                   __mpt3sas_get_sdev_by_addr() function.
> 
> [Chaitra]Here instead of calling " __mpt3sas_get_sdev_by_handle()" function
> calling
> 	"mpt3sas_get_sdev_by_handle()" function will fixes "invalid page access"
> type of kernel panic
> 
> > -       sas_device = _scsih_sas_device_find_by_handle(ioc, handle);
> > +       sas_device = __mpt3sas_get_sdev_by_handle(ioc, handle);
> >         if (!sas_device)
> >                 return;
> >

Whoops, missed this comment in _scsih_block_io_device() from Sreekanth's
earlier reply.

Here's the updated incremental patch atop target-pending/for-next-merge
to use the protected callers for both cases.

Please review + ACK ASAP.

Thank you,

--nab