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From: Matthew Wilcox <willy@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: "Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Theodore Ts'o" <tytso@mit.edu>,
	"Jeff Layton" <jlayton@kernel.org>,
	linux-xfs@vger.kernel.org,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org,
	linux-mm@kvack.org, "Jason Gunthorpe" <jgg@ziepe.ca>,
	linux-rdma@vger.kernel.org
Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal
Date: Wed, 12 Jun 2019 05:37:53 -0700	[thread overview]
Message-ID: <20190612123751.GD32656@bombadil.infradead.org> (raw)
In-Reply-To: <20190608001036.GF14308@dread.disaster.area>

On Sat, Jun 08, 2019 at 10:10:36AM +1000, Dave Chinner wrote:
> On Fri, Jun 07, 2019 at 11:25:35AM -0700, Ira Weiny wrote:
> > Are you suggesting that we have something like this from user space?
> > 
> > 	fcntl(fd, F_SETLEASE, F_LAYOUT | F_UNBREAKABLE);
> 
> Rather than "unbreakable", perhaps a clearer description of the
> policy it entails is "exclusive"?
> 
> i.e. what we are talking about here is an exclusive lease that
> prevents other processes from changing the layout. i.e. the
> mechanism used to guarantee a lease is exclusive is that the layout
> becomes "unbreakable" at the filesystem level, but the policy we are
> actually presenting to uses is "exclusive access"...

That's rather different from the normal meaning of 'exclusive' in the
context of locks, which is "only one user can have access to this at
a time".  As I understand it, this is rather more like a 'shared' or
'read' lock.  The filesystem would be the one which wants an exclusive
lock, so it can modify the mapping of logical to physical blocks.

The complication being that by default the filesystem has an exclusive
lock on the mapping, and what we're trying to add is the ability for
readers to ask the filesystem to give up its exclusive lock.


  parent reply	other threads:[~2019-06-12 12:38 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-06  1:45 [PATCH RFC 00/10] RDMA/FS DAX truncate proposal ira.weiny
2019-06-06  1:45 ` [PATCH RFC 01/10] fs/locks: Add trace_leases_conflict ira.weiny
2019-06-09 12:52   ` Jeff Layton
2019-06-06  1:45 ` [PATCH RFC 02/10] fs/locks: Export F_LAYOUT lease to user space ira.weiny
2019-06-09 13:00   ` Jeff Layton
2019-06-11 21:38     ` Ira Weiny
2019-06-12  9:46       ` Jan Kara
2019-06-06  1:45 ` [PATCH RFC 03/10] mm/gup: Pass flags down to __gup_device_huge* calls ira.weiny
2019-06-06  6:18   ` Christoph Hellwig
2019-06-06 16:10     ` Ira Weiny
2019-06-06  1:45 ` [PATCH RFC 04/10] mm/gup: Ensure F_LAYOUT lease is held prior to GUP'ing pages ira.weiny
2019-06-06  1:45 ` [PATCH RFC 05/10] fs/ext4: Teach ext4 to break layout leases ira.weiny
2019-06-06  1:45 ` [PATCH RFC 06/10] fs/ext4: Teach dax_layout_busy_page() to operate on a sub-range ira.weiny
2019-06-06  1:45 ` [PATCH RFC 07/10] fs/ext4: Fail truncate if pages are GUP pinned ira.weiny
2019-06-06 10:58   ` Jan Kara
2019-06-06 16:17     ` Ira Weiny
2019-06-06  1:45 ` [PATCH RFC 08/10] fs/xfs: Teach xfs to use new dax_layout_busy_page() ira.weiny
2019-06-06  1:45 ` [PATCH RFC 09/10] fs/xfs: Fail truncate if pages are GUP pinned ira.weiny
2019-06-06  1:45 ` [PATCH RFC 10/10] mm/gup: Remove FOLL_LONGTERM DAX exclusion ira.weiny
2019-06-06  5:52 ` [PATCH RFC 00/10] RDMA/FS DAX truncate proposal John Hubbard
2019-06-06 17:11   ` Ira Weiny
2019-06-06 19:46     ` Jason Gunthorpe
2019-06-06 10:42 ` Jan Kara
2019-06-06 15:35   ` Dan Williams
2019-06-06 19:51   ` Jason Gunthorpe
2019-06-06 22:22     ` Ira Weiny
2019-06-07 10:36       ` Jan Kara
2019-06-07 12:17         ` Jason Gunthorpe
2019-06-07 14:52           ` Ira Weiny
2019-06-07 15:10             ` Jason Gunthorpe
2019-06-12 10:29             ` Jan Kara
2019-06-12 11:47               ` Jason Gunthorpe
2019-06-12 12:09                 ` Jan Kara
2019-06-12 18:41                   ` Dan Williams
2019-06-13  7:17                     ` Jan Kara
2019-06-12 19:14                   ` Jason Gunthorpe
2019-06-12 22:13                     ` Ira Weiny
2019-06-12 22:54                       ` Dan Williams
2019-06-12 23:33                         ` Ira Weiny
2019-06-13  1:14                           ` Dan Williams
2019-06-13 15:13                             ` Jason Gunthorpe
2019-06-13 16:25                               ` Dan Williams
2019-06-13 17:18                                 ` Jason Gunthorpe
2019-06-13 16:53                           ` Dan Williams
2019-06-13 15:12                         ` Jason Gunthorpe
2019-06-13  7:53                       ` Jan Kara
2019-06-12 18:49               ` Dan Williams
2019-06-13  7:43                 ` Jan Kara
2019-06-06 22:03   ` Ira Weiny
2019-06-06 22:26     ` Ira Weiny
2019-06-06 22:28     ` Dave Chinner
2019-06-07 11:04     ` Jan Kara
2019-06-07 18:25       ` Ira Weiny
2019-06-07 18:50         ` Jason Gunthorpe
2019-06-08  0:10         ` Dave Chinner
2019-06-09  1:29           ` Ira Weiny
2019-06-12 12:37           ` Matthew Wilcox [this message]
2019-06-12 23:30             ` Ira Weiny
2019-06-13  0:55               ` Dave Chinner
2019-06-13 20:34                 ` Ira Weiny
2019-06-14  3:42                   ` Dave Chinner
2019-06-13  0:25             ` Dave Chinner
2019-06-13  3:23               ` Matthew Wilcox
2019-06-13  4:36                 ` Dave Chinner
2019-06-13 10:47                   ` Matthew Wilcox
2019-06-13 15:29                 ` Jason Gunthorpe
2019-06-13 15:27               ` Matthew Wilcox
2019-06-13 21:13                 ` Ira Weiny
2019-06-13 23:45                   ` Jason Gunthorpe
2019-06-14  0:00                     ` Ira Weiny
2019-06-14  2:09                     ` Dave Chinner
2019-06-14  2:31                       ` Matthew Wilcox
2019-06-14  3:07                         ` Dave Chinner
2019-06-20 14:52                 ` Jan Kara
2019-06-13 20:34               ` Ira Weiny
2019-06-14  2:58                 ` Dave Chinner

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