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From: Matthew Wilcox <willy@linux.intel.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk,
	boaz@plexistor.com, david@fromorbit.com,
	linux-arch@vger.kernel.org, arnd@arndb.de,
	ross.zwisler@linux.intel.com, linux-nvdimm@ml01.01.org,
	benh@kernel.crashing.org, linux-fsdevel@vger.kernel.org,
	heiko.carstens@de.ibm.com, hch@lst.de, tj@kernel.org,
	paulus@samba.org, hpa@zytor.com, schwidefsky@de.ibm.com,
	akpm@linux-foundation.org, torvalds@linux-foundation.org,
	mingo@kernel.org
Subject: Re: [PATCH v4 3/9] dax: drop size parameter to ->direct_access()
Date: Sat, 6 Jun 2015 07:37:40 -0400	[thread overview]
Message-ID: <20150606113739.GH2729@linux.intel.com> (raw)
In-Reply-To: <20150605211918.20751.21557.stgit@dwillia2-desk3.amr.corp.intel.com>

On Fri, Jun 05, 2015 at 05:19:18PM -0400, Dan Williams wrote:
> None of the implementations currently use it.  The common
> bdev_direct_access() entry point handles all the size checks before
> calling ->direct_access().

Interesting.  The reason it was still there, even after moving all
the size checks to bdev_direct_access() was to support the case of a
hypothetical future driver that exposed several discontiguous ranges as
a single block device.

But we don't actually need it for that, as long as the discontiguous
ranges are relatively large.  As the comment you deleted noted, the brd
driver could do this, but I certainly haven't taken the time to figure
out whether it'd be a performance win if the pages "just happen" to line
up right.

So I don't think I'm objecting to this patch (except that it conflicts
textually with my dynamic mapping patch that you've seen but hasn't been
posted publically yet).  Just something to think about.

  reply	other threads:[~2015-06-06 11:37 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-06-05 21:19 [PATCH v4 0/9] introduce __pfn_t, evacuate struct page from sgls Dan Williams
2015-06-05 21:19 ` [PATCH v4 1/9] introduce __pfn_t for scatterlists and pmem Dan Williams
2015-06-05 21:37   ` Linus Torvalds
2015-06-05 22:12     ` Dan Williams
2015-06-05 21:19 ` [PATCH v4 2/9] x86: support kmap_atomic_pfn_t() for persistent memory Dan Williams
2015-06-09  6:50   ` Christoph Hellwig
2015-06-10 12:12   ` Christoph Hellwig
2015-06-10 15:03     ` Matthew Wilcox
2015-06-10 15:11       ` Christoph Hellwig
2015-06-10 15:36         ` Dan Williams
2015-06-10 16:11           ` Christoph Hellwig
2015-06-10 16:17             ` Dan Williams
2015-06-05 21:19 ` [PATCH v4 3/9] dax: drop size parameter to ->direct_access() Dan Williams
2015-06-06 11:37   ` Matthew Wilcox [this message]
2015-06-09  6:51   ` Christoph Hellwig
2015-06-05 21:19 ` [PATCH v4 4/9] dax: fix mapping lifetime handling, convert to __pfn_t + kmap_atomic_pfn_t() Dan Williams
2015-06-06 11:58   ` Matthew Wilcox
2015-08-07 23:54     ` Dan Williams
2015-06-08 16:29   ` Elliott, Robert (Server Storage)
2015-06-08 16:36     ` Dan Williams
2015-06-09  6:55   ` Christoph Hellwig
2015-06-05 21:19 ` [PATCH v4 5/9] dma-mapping: allow archs to optionally specify a ->map_pfn() operation Dan Williams
2015-06-05 21:19 ` [PATCH v4 6/9] scatterlist: use sg_phys() Dan Williams
2015-06-09  6:59   ` Christoph Hellwig
2015-06-05 21:19 ` [PATCH v4 7/9] scatterlist: cleanup sg_chain() and sg_unmark_end() Dan Williams
2015-06-05 21:19 ` [PATCH v4 8/9] scatterlist: convert to __pfn_t Dan Williams
2015-06-05 21:19 ` [PATCH v4 9/9] x86: convert dma_map_ops to support mapping a __pfn_t Dan Williams
2015-06-09  6:58   ` Christoph Hellwig
2015-06-09 13:47     ` Konrad Rzeszutek Wilk
2015-06-05 21:23 ` [PATCH v4 0/9] introduce __pfn_t, evacuate struct page from sgls Dan Williams

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