From: Christoph Hellwig <hch@lst.de>
To: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>,
akpm@linux-foundation.org, Michal Hocko <mhocko@suse.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Dave Chinner <david@fromorbit.com>,
"J. Bruce Fields" <bfields@fieldses.org>,
linux-mm@kvack.org, Paul Mackerras <paulus@samba.org>,
Sean Hefty <sean.hefty@intel.com>,
Jeff Layton <jlayton@poochiereds.net>,
Matthew Wilcox <mawilcox@microsoft.com>,
linux-rdma@vger.kernel.org, Michael Ellerman <mpe@ellerman.id.au>,
Jeff Moyer <jmoyer@redhat.com>,
Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
Doug Ledford <dledford@redhat.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Hal Rosenstock <hal.rosenstock@gmail.com>,
Heiko
Subject: Re: [PATCH v3 00/13] dax: fix dma vs truncate and remove 'page-less' support
Date: Fri, 27 Oct 2017 08:45:27 +0200 [thread overview]
Message-ID: <20171027064526.GD22931@lst.de> (raw)
In-Reply-To: <20171026105850.GA31161@quack2.suse.cz>
On Thu, Oct 26, 2017 at 12:58:50PM +0200, Jan Kara wrote:
> But are we guaranteed page refs are short term? E.g. if someone creates
> v4l2 videobuf in MAP_SHARED mapping of a file on DAX filesystem, page refs
> can be rather long-term similarly as in RDMA case. Also freeing of blocks
> on page reference drop is another async entry point into the filesystem
> which could unpleasantly surprise us but I guess workqueues would solve
> that reasonably fine.
The point is that we need to prohibit long term elevated page counts
with DAX anyway - we can't just let people grab allocated blocks forever
while ignoring file system operations. For stage 1 we'll just need to
fail those, and in the long run they will have to use a mechanism
similar to FL_LAYOUT locks to deal with file system allocation changes.
next prev parent reply other threads:[~2017-10-27 6:45 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-20 2:38 [PATCH v3 00/13] dax: fix dma vs truncate and remove 'page-less' support Dan Williams
2017-10-20 2:39 ` [PATCH v3 09/13] IB/core: disable memory registration of fileystem-dax vmas Dan Williams
2017-10-20 7:47 ` [PATCH v3 00/13] dax: fix dma vs truncate and remove 'page-less' support Christoph Hellwig
2017-10-20 9:31 ` Christoph Hellwig
2017-10-26 10:58 ` Jan Kara
2017-10-26 23:51 ` Williams, Dan J
2017-10-27 6:48 ` Dave Chinner
2017-10-27 11:42 ` Dan Williams
2017-10-29 21:52 ` Dave Chinner
2017-10-27 6:45 ` Christoph Hellwig [this message]
2017-10-29 23:46 ` Dan Williams
2017-10-30 2:00 ` Dave Chinner
2017-10-30 8:38 ` Jan Kara
2017-10-30 11:20 ` Dave Chinner
2017-10-30 17:51 ` Dan Williams
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