From: Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
To: Tony Battersby <tonyb-vFAe+i1/wJI5UWNf+nJyDw@public.gmane.org>
Cc: linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Chaitra P B
<chaitra.basappa-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>,
Suganath Prabu Subramani
<suganath-prabu.subramani-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>,
Sathya Prakash
<sathya.prakash-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
MPT-FusionLinux.pdl-dY08KVG/lbpWk0Htik3J/w@public.gmane.org,
Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
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-vFAe+i1/wJI5UWNf+nJyDw@public.gmane.org>
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
[not found] ` <eabf88b3-c40f-9973-efed-30af46f42c8d-vFAe+i1/wJI5UWNf+nJyDw@public.gmane.org>
2018-08-03 20:05 ` Tony Battersby
[not found] ` <fee77a48-a86b-75eb-7648-6e6e13c3e8e8-vFAe+i1/wJI5UWNf+nJyDw@public.gmane.org>
2018-08-03 21:02 ` Matthew Wilcox [this message]
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