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From: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
To: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Cc: Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>,
	"Darrick J. Wong"
	<darrick.wong-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
	Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	"linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org"
	<linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>,
	Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>,
	"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
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	Linux MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
	Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Alexander Viro
	<viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
	Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	linux-fsdevel
	<linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Ross Zwisler
	<ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
	xen-devel-GuqFBffKawuEi8DpZVb4nw@public.gmane.org
Subject: Re: [PATCH v6 4/5] fs, xfs: introduce MAP_DIRECT for creating block-map-atomic file ranges
Date: Thu, 24 Aug 2017 13:26:55 -0700	[thread overview]
Message-ID: <CAPcyv4j06mdEek-aYfZCbTW0MaL6gy7OpUsgyv4hBB5yy_rW6A@mail.gmail.com> (raw)
In-Reply-To: <20170824163925.GA28503-jcswGhMUV9g@public.gmane.org>

On Thu, Aug 24, 2017 at 9:39 AM, Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org> wrote:
> On Thu, Aug 24, 2017 at 09:31:17AM -0700, Dan Williams wrote:
>> External agent is a DMA device, or a hypervisor like Xen. In the DMA
>> case perhaps we can use the fcntl lease mechanism, I'll investigate.
>> In the Xen case it actually would need to use fiemap() to discover the
>> physical addresses that back the file to setup their M2P tables.
>> Here's the discussion where we discovered that physical address
>> dependency:
>>
>>     https://lists.xen.org/archives/html/xen-devel/2017-04/msg00419.html
>
> fiemap does not work to discover physical addresses.  If they want
> to do anything involving physical address they will need a kernel
> driver.

True, it's broken with respect to multi-device filesystems and these
patches do nothing to fix that problem. Ok, I'm fine to let that use
case depend on a kernel driver and just focus on fixing the DMA case.

  parent reply	other threads:[~2017-08-24 20:26 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-23 23:48 [PATCH v6 0/5] MAP_DIRECT and block-map-atomic files Dan Williams
     [not found] ` <150353211413.5039.5228914877418362329.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-08-23 23:48   ` [PATCH v6 1/5] vfs: add flags parameter to ->mmap() in 'struct file_operations' Dan Williams
     [not found]     ` <150353211985.5039.4333061601382775843.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-08-24 16:58       ` Christoph Hellwig
2017-08-24 17:42         ` Dan Williams
2017-08-23 23:48   ` [PATCH v6 2/5] fs, xfs: introduce S_IOMAP_SEALED Dan Williams
     [not found]     ` <150353212577.5039.14069456126848863439.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-08-24 16:13       ` Christoph Hellwig
2017-08-25  6:00         ` Dan Williams
2017-08-25 19:44           ` Dan Williams
2017-08-23 23:48   ` [PATCH v6 4/5] fs, xfs: introduce MAP_DIRECT for creating block-map-atomic file ranges Dan Williams
     [not found]     ` <150353213655.5039.7662200155640827407.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-08-24 16:11       ` Christoph Hellwig
     [not found]         ` <20170824161152.GB27591-jcswGhMUV9g@public.gmane.org>
2017-08-24 16:31           ` Dan Williams
2017-08-24 16:39             ` Christoph Hellwig
     [not found]               ` <20170824163925.GA28503-jcswGhMUV9g@public.gmane.org>
2017-08-24 20:26                 ` Dan Williams [this message]
2017-08-23 23:49   ` [PATCH v6 5/5] fs, fcntl: add F_MAP_DIRECT Dan Williams
2017-08-23 23:48 ` [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Dan Williams
     [not found]   ` <150353213097.5039.6729469069608762658.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-08-24 13:04     ` Jan Kara
2017-08-24 16:55     ` Christoph Hellwig
     [not found]       ` <20170824165546.GA3121-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2017-08-24 17:36         ` Dan Williams
     [not found]           ` <CAPcyv4iN0QpUSgOUvisnNQsiV1Pp=4dh7CwAV8FFj=_rFU=aug-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-25 13:00             ` Christoph Hellwig
2017-08-25 15:58               ` Kirill A. Shutemov
2017-08-25 16:02                 ` Christoph Hellwig
2017-08-25 16:16                   ` Kirill A. Shutemov
     [not found]                     ` <20170825161607.6v6beg4zjktllt2z-sVvlyX1904swdBt8bTSxpkEMvNT87kid@public.gmane.org>
2017-08-25 16:19                       ` Helge Deller
2017-08-25 16:56                         ` Kirill A. Shutemov
2017-08-25 20:24                         ` Dan Williams
     [not found]                           ` <CAPcyv4jeZc8P+E0aHNChzy-wfNpOx3GehKck1nXqJ1b9JdydFA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-26  7:40                             ` Helge Deller
2017-08-26 15:15                               ` Dan Williams
     [not found]                                 ` <CAPcyv4ic0zxQzWEipZ=1LpDC8VnmphGzVSYmrFcjOAgX7esfUw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-26 19:50                                   ` Helge Deller
2017-08-26 22:46                                     ` Dan Williams
2017-08-26 23:56                                       ` Kirill A. Shutemov
2017-08-24 16:08 ` [PATCH v6 0/5] MAP_DIRECT and block-map-atomic files Christoph Hellwig
2017-08-24 16:25   ` Dan Williams

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