Re: [PATCH] mpt3sas: Fix kernel panic observed on soft HBA unplug

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On Wed, Mar 11, 2020 at 4:35 PM Amit Shah <amit@xxxxxxxxxx> wrote:
>
> On Wed, 2020-03-11 at 06:36 -0400, Sreekanth Reddy wrote:
> > Generic protection fault type kernel panic is observed when user
> > performs soft(ordered) HBA unplug operation while IOs are running
> > on drives connected to HBA.
> >
> > When user performs ordered HBA removal operation then kernel calls
> > PCI device's .remove() call back function where driver is flushing
> > out
> > all the outstanding SCSI IO commands with DID_NO_CONNECT host byte
> > and
> > also un-maps sg buffers allocated for these IO commands.
> > But in the ordered HBA removal case (unlike of real HBA hot unplug)
> > HBA device is still alive and hence HBA hardware is performing the
> > DMA operations to those buffers on the system memory which are
> > already
> > unmapped while flushing out the outstanding SCSI IO commands
> > and this leads to Kernel panic.
> >
> > Fix:
> > Don't flush out the outstanding IOs from .remove() path in case of
> > ordered HBA removal since HBA will be still alive in this case and
> > it can complete the outstanding IOs. Flush out the outstanding IOs
> > only in case physical HBA hot unplug where their won't be any
> > communication with the HBA.
>
> Can you please point to the commit that introduces the bug?

Sure I will add the commit ID which introduced this bug in the next patch.

>
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Sreekanth Reddy <sreekanth.reddy@xxxxxxxxxxxx>
> > ---
> >  drivers/scsi/mpt3sas/mpt3sas_scsih.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> > b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> > index 778d5e6..04a40af 100644
> > --- a/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> > +++ b/drivers/scsi/mpt3sas/mpt3sas_scsih.c
> > @@ -9908,8 +9908,8 @@ static void scsih_remove(struct pci_dev *pdev)
> >
> >       ioc->remove_host = 1;
> >
> > -     mpt3sas_wait_for_commands_to_complete(ioc);
> > -     _scsih_flush_running_cmds(ioc);
> > +     if (!pci_device_is_present(pdev))
> > +             _scsih_flush_running_cmds(ioc);
> >
> >       _scsih_fw_event_cleanup_queue(ioc);
> >
> > @@ -9992,8 +9992,8 @@ static void scsih_remove(struct pci_dev *pdev)
>
> Just a note: this function is scsih_shutdown().  Doesn't block
> application of the patch, though.  Just wondering how the patch was
> created.

Sorry I didn't get you. Can you please elaborate your query?

>
> >
> >       ioc->remove_host = 1;
> >
> > -     mpt3sas_wait_for_commands_to_complete(ioc);
> > -     _scsih_flush_running_cmds(ioc);
> > +     if (!pci_device_is_present(pdev))
> > +             _scsih_flush_running_cmds(ioc);
> >
> >       _scsih_fw_event_cleanup_queue(ioc);
> >
>



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