Re: PATCH [2/8] scsi: megaraid_sas - add module param fast_load

Christoph Hellwig
2007-10-30T17:36:48Z

On Mon, Oct 01, 2007 at 11:46:51AM -0400, bo yang wrote:
> +/*
> + * Fast driver load option, skip scanning for physical devices during
> + * load. This would result in physical devices being skipped during
> + * driver load time. These can be later added though,
> + * using /proc/scsi/scsi
> + */

/proc/scsi/scsi is deprecated, so please don't recommend it here.
The proper way is the scan attribute of the scsi host.

> +static unsigned int fast_load;
> +module_param_named(fast_load, fast_load, int, 0);
> +MODULE_PARM_DESC(fast_load,
> + "megasas: Faster loading of the driver, skips physical devices! "\
> + "(default = 0)");

This should show up in sysfs.

> +static struct megasas_instance *megasas_lookup_instance(u16 host_no)
> +{
> + int i;
> +
> + for (i = 0; i < megasas_mgmt_info.max_index; i++) {
> + if ((megasas_mgmt_info.instance[i]) &&
> + (megasas_mgmt_info.instance[i]->host->host_no
> + == host_no))

no need for the braces here. This should be:

if (megasas_mgmt_info.instance[i] &&
megasas_mgmt_info.instance[i]->host->host_no == host_no)

> +static int megasas_slave_alloc(struct scsi_device *sdev)
> +{
> + struct megasas_instance *instance;
> + int tmp_fastload = fast_load;
> +
> + instance = megasas_lookup_instance(sdev->host->host_no);
> +
> + if (tmp_fastload && sdev->channel < MEGASAS_MAX_PD_CHANNELS) {
> + if ((sdev->id == MEGASAS_MAX_DEV_PER_CHANNEL -1) &&
> + (sdev->channel == MEGASAS_MAX_PD_CHANNELS - 1)) {
> +
> + /*
> + * If fast load option was set and scan for last device is
> + * over, reset the fast_load flag so that during a possible
> + * next scan, devices can be made available
> + */
> + fast_load = 0;
> + }
> + return -ENXIO;
> + }
> +
> + return 0;
> +}

This is a rather complicated and fragile way to implement this feature.

I'd recomment to change the call to scsi_scan_host in megasas_io_attach
to something like:

if (fast_load) {
int channel;

for (channel = 0; channel < MEGASAS_MAX_PD_CHANNELS;
channel++) {
scsi_scan_host_selected(host, channel, SCAN_WILD_CARD,
SCAN_WILD_CARD, 0);
}
} else {
scsi_scan_host(host);
}