linux-kernel - Re: [PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary restriction for the module parameter max_sgl

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Date:	Thu, 11 Dec 2014 17:44:03 +0530
From:	Sreekanth Reddy <sreekanth.reddy@...gotech.com>
To:	"Martin K. Petersen" <martin.petersen@...cle.com>
Cc:	"jejb@...nel.org" <jejb@...nel.org>,
	Christoph Hellwig <hch@...radead.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	Sathya Prakash <Sathya.Prakash@...gotech.com>,
	Nagalakshmi Nandigama <Nagalakshmi.Nandigama@...gotech.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/22] [SCSI] mpt2sas, mpt3sas: Removing uppper boundary
 restriction for the module parameter max_sgl_entries

> @@ -2486,9 +2486,13 @@ _base_allocate_memory_pools(struct MPT2SAS_ADAPTER *ioc,  int sleep_flag)
>
>         /* command line tunables  for max sgl entries */
>         if (max_sgl_entries != -1) {
> -               ioc->shost->sg_tablesize = (max_sgl_entries <
> -                   MPT2SAS_SG_DEPTH) ? max_sgl_entries :
> -                   MPT2SAS_SG_DEPTH;
> +               if (max_sgl_entries > MPT2SAS_SG_DEPTH)
> +                       printk(MPT2SAS_WARN_FMT
> +                        "setting max_sgl_entries(%d), overriding kernel"
> +                        " defined SCSI_MAX_SG_SEGMENTS(%d)\n", ioc->name,
> +                         max_sgl_entries, MPT2SAS_SG_DEPTH);
> +               ioc->shost->sg_tablesize =  min_t(unsigned short,
> +                            max_sgl_entries, SCSI_MAX_SG_CHAIN_SEGMENTS);
>         } else {
>                 ioc->shost->sg_tablesize = MPT2SAS_SG_DEPTH;
>         }
>
> Wouldn't it be better to print the new scatterlist limit after it has
> been clamped to reflect what it's actually being set to?

but Martin, I though to warn the user that the module parameter
max_sgl_entries value what they provided is greater than the kernel
defined SCSI_MAX_SG_SEGMENTS, whether if this module parameter value
is greater than or less than the SCSI_MAX_SG_CHAIN_SEGMENTS. Also I
thought, user may confuse if see observes SCSI_MAX_SG_CHAIN_SEGMENTS
value instead of max_sgl_entries value in the warning message.

Please let me known If my assumption is wrong. Then I will modify this
patch according to your suggestion i.e I will print the scatterlist
limit after it has been clamped.

Thanks,
Sreekanth
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