From: Matthew Wilcox <willy@infradead.org>
To: Tony Battersby <tonyb@cybernetics.com>
Cc: Christoph Hellwig <hch@lst.de>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Sathya Prakash <sathya.prakash@broadcom.com>,
Chaitra P B <chaitra.basappa@broadcom.com>,
Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>,
iommu@lists.linux-foundation.org, linux-mm@kvack.org,
linux-scsi@vger.kernel.org, MPT-FusionLinux.pdl@broadcom.com
Subject: Re: [PATCH v2 6/9] dmapool: improve scalability of dma_pool_free
Date: Fri, 3 Aug 2018 14:02:15 -0700 [thread overview]
Message-ID: <20180803210215.GA9329@bombadil.infradead.org> (raw)
In-Reply-To: <fee77a48-a86b-75eb-7648-6e6e13c3e8e8@cybernetics.com>
On Fri, Aug 03, 2018 at 04:05:35PM -0400, Tony Battersby wrote:
> For v3 of the patchset, I was also considering to add a note to the
> kernel-doc comments for dma_pool_create() to use dma_alloc_coherent()
> directly instead of a dma pool if the driver intends to allow userspace
> to mmap() the returned pages, due to the new use of the _mapcount union
> in struct page. Would you consider that useful information or pointless
> trivia?
If userspace is going to map the pages, it's going to expose other things
to userspace than the dma pages. I'd suggest they not do this; they
should do their own sub-allocation which only exposes to an individual
task the data they're sure is OK for each task to see.
prev parent reply other threads:[~2018-08-03 21:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-02 19:59 [PATCH v2 6/9] dmapool: improve scalability of dma_pool_free Tony Battersby
2018-08-03 20:05 ` Tony Battersby
2018-08-03 21:02 ` Matthew Wilcox [this message]
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