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-   -   scsi_dh_rdac: Changing the memory allocation flag from GFP_KERNEL to GFP_NOIO (http://www.linux-archive.org/device-mapper-development/316064-scsi_dh_rdac-changing-memory-allocation-flag-gfp_kernel-gfp_noio.html)

Chandra Seetharaman 01-27-2010 09:19 PM

scsi_dh_rdac: Changing the memory allocation flag from GFP_KERNEL to GFP_NOIO
 
Acked-by: Chandra Seetharaman <sekharan@us.ibm.com>

On Tue, 2010-01-05 at 10:20 -0700, Moger, Babu wrote:
> This patch changes the memory allocation flag from GFP_KERNEL to GFP_NOIO which is more appropriate.
>
> This was noticed by Mike Christie and Rob Evers..
> Mike Christie wrote:
> > Rob Evers wrote:
> >> +
> >> +static int queue_mode_select(struct scsi_device *sdev,
> >> + activate_complete fn, void *data)
> >> +{
> >> + struct rdac_queue_data *qdata;
> >> + struct rdac_controller *ctlr;
> >> +
> >> + qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
> >> + if (!qdata)
> >> + return SCSI_DH_RETRY;
> >> +
> >
> > It looks like this is called in the main IO path. A failed IO could cause, the path to go down,
> > then we would call this to active a new path. If the system needed to write out pages to the same
> > disk that just had the failed path so it can allocate memory then GFP_KERNEL would be bad to use here.
> > You would use a mempool and still use something like GFP_NOIO. If a mempool is not possible for some
> > reason, then you would want to still use GFP_NOIO.
>
> Using mempool would become bit more complex here because I cannot assume about the number of elements
> during the allocation. I would use GFP_NOIO.
>
> CC: Mike Christie <michaelc@cs.wisc.edu>
> CC: Rob Evers <revers@redhat.com>
> CC: Chandra Seetharaman <chandra.seetharaman@us.ibm.com>
> Signed-off-by: Babu Moger <babu.moger@lsi.com>
>
> ---
> --- linux-2.6.33-rc2/drivers/scsi/device_handler/scsi_dh_rdac.c.orig 2010-01-05 11:49:22.000000000 -0400
> +++ linux-2.6.33-rc2/drivers/scsi/device_handler/scsi_dh_rdac.c 2010-01-05 11:53:13.000000000 -0400
> @@ -624,7 +624,7 @@ static int queue_mode_select(struct scsi
> struct rdac_queue_data *qdata;
> struct rdac_controller *ctlr;
>
> - qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
> + qdata = kzalloc(sizeof(*qdata), GFP_NOIO);
> if (!qdata)
> return SCSI_DH_RETRY;
>
>
>
>
> --
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> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel

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