linux-kernel - Re: [PATCH 4/5] scsi: megaraid_sas - preallocate memory for ioctl processing

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Date:	Thu, 8 Feb 2007 19:38:27 +0000
From:	Christoph Hellwig <hch@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Sumant Patro <sumantp@...l.com>, James.Bottomley@...elEye.com,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	neela.kolli@....com, bo.yang@....com, sumant.patro@....com
Subject: Re: [PATCH 4/5] scsi: megaraid_sas - preallocate memory for ioctl processing

On Wed, Feb 07, 2007 at 01:30:20PM -0800, Andrew Morton wrote:
> On Tue, 06 Feb 2007 14:19:54 -0800
> Sumant Patro <sumantp@...l.com> wrote:
> 
> > Preallocate memory for ioctl processing. This is to avoid situations 
> > where ioctl fails for lack of memory (when system under heavy stress).
> > The memory pool will have 8*4K, 4*8K and 1*64K memory chunks
> 
> mutter.
> 
> I suspect all this horror is due to stupidity in the DMA API.
> 
> pci_alloc_consistent() just goes and assumes GFP_ATOMIC, whereas
> the caller (megasas_mgmt_fw_ioctl) would have been perfectly happy
> to use GFP_KERNEL.
> 
> I bet this fixes it:

but it's ugly as hell, why there is a much more trivial fix for it:
simply use dma_alloc_coherent.

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