From: Ira Weiny <ira.weiny@intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Michal Hocko <mhocko@suse.com>, Theodore Ts'o <tytso@mit.edu>,
linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org,
John Hubbard <jhubbard@nvidia.com>,
linux-kernel@vger.kernel.org,
Matthew Wilcox <willy@infradead.org>,
linux-xfs@vger.kernel.org, Jason Gunthorpe <jgg@ziepe.ca>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
linux-ext4@vger.kernel.org
Subject: Re: [RFC PATCH v2 01/19] fs/locks: Export F_LAYOUT lease to user space
Date: Mon, 12 Aug 2019 10:36:26 -0700 [thread overview]
Message-ID: <20190812173626.GB19746@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20190809235231.GC7777@dread.disaster.area>
On Sat, Aug 10, 2019 at 09:52:31AM +1000, Dave Chinner wrote:
> On Fri, Aug 09, 2019 at 03:58:15PM -0700, ira.weiny@intel.com wrote:
> > From: Ira Weiny <ira.weiny@intel.com>
> >
> > In order to support an opt-in policy for users to allow long term pins
> > of FS DAX pages we need to export the LAYOUT lease to user space.
> >
> > This is the first of 2 new lease flags which must be used to allow a
> > long term pin to be made on a file.
> >
> > After the complete series:
> >
> > 0) Registrations to Device DAX char devs are not affected
> >
> > 1) The user has to opt in to allowing page pins on a file with an exclusive
> > layout lease. Both exclusive and layout lease flags are user visible now.
> >
> > 2) page pins will fail if the lease is not active when the file back page is
> > encountered.
> >
> > 3) Any truncate or hole punch operation on a pinned DAX page will fail.
> >
> > 4) The user has the option of holding the lease or releasing it. If they
> > release it no other pin calls will work on the file.
> >
> > 5) Closing the file is ok.
> >
> > 6) Unmapping the file is ok
> >
> > 7) Pins against the files are tracked back to an owning file or an owning mm
> > depending on the internal subsystem needs. With RDMA there is an owning
> > file which is related to the pined file.
> >
> > 8) Only RDMA is currently supported
> >
> > 9) Truncation of pages which are not actively pinned nor covered by a lease
> > will succeed.
>
> This has nothing to do with layout leases or what they provide
> access arbitration over. Layout leases have _nothing_ to do with
> page pinning or RDMA - they arbitrate behaviour the file offset ->
> physical block device mapping within the filesystem and the
> behaviour that will occur when a specific lease is held.
>
> The commit descripting needs to describe what F_LAYOUT actually
> protects, when they'll get broken, etc, not how RDMA is going to use
> it.
Ok yes I've been lax in mixing the cover letter for the series and this first
commit message. My apologies.
>
> > @@ -2022,8 +2030,26 @@ static int do_fcntl_add_lease(unsigned int fd, struct file *filp, long arg)
> > struct file_lock *fl;
> > struct fasync_struct *new;
> > int error;
> > + unsigned int flags = 0;
> > +
> > + /*
> > + * NOTE on F_LAYOUT lease
> > + *
> > + * LAYOUT lease types are taken on files which the user knows that
> > + * they will be pinning in memory for some indeterminate amount of
> > + * time.
>
> Indeed, layout leases have nothing to do with pinning of memory.
Yep, Fair enough. I'll rework the comment.
> That's something an application taht uses layout leases might do,
> but it largely irrelevant to the functionality layout leases
> provide. What needs to be done here is explain what the layout lease
> API actually guarantees w.r.t. the physical file layout, not what
> some application is going to do with a lease. e.g.
>
> The layout lease F_RDLCK guarantees that the holder will be
> notified that the physical file layout is about to be
> changed, and that it needs to release any resources it has
> over the range of this lease, drop the lease and then
> request it again to wait for the kernel to finish whatever
> it is doing on that range.
>
> The layout lease F_RDLCK also allows the holder to modify
> the physical layout of the file. If an operation from the
> lease holder occurs that would modify the layout, that lease
> holder does not get notification that a change will occur,
> but it will block until all other F_RDLCK leases have been
> released by their holders before going ahead.
>
> If there is a F_WRLCK lease held on the file, then a F_RDLCK
> holder will fail any operation that may modify the physical
> layout of the file. F_WRLCK provides exclusive physical
> modification access to the holder, guaranteeing nothing else
> will change the layout of the file while it holds the lease.
>
> The F_WRLCK holder can change the physical layout of the
> file if it so desires, this will block while F_RDLCK holders
> are notified and release their leases before the
> modification will take place.
>
> We need to define the semantics we expose to userspace first.....
Agreed. I believe I have implemented the semantics you describe above. Do I
have your permission to use your verbiage as part of reworking the comment and
commit message?
Thanks,
Ira
>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@fromorbit.com
>
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next prev parent reply other threads:[~2019-08-12 17:38 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-09 22:58 [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 01/19] fs/locks: Export F_LAYOUT lease to user space ira.weiny
2019-08-09 23:52 ` Dave Chinner
2019-08-12 17:36 ` Ira Weiny [this message]
2019-08-14 8:05 ` Dave Chinner
2019-08-14 11:21 ` Jeff Layton
2019-08-14 11:38 ` Dave Chinner
2019-08-09 22:58 ` [RFC PATCH v2 02/19] fs/locks: Add Exclusive flag to user Layout lease ira.weiny
2019-08-14 14:15 ` Jeff Layton
2019-08-14 21:56 ` Dave Chinner
2019-08-26 10:41 ` Jeff Layton
2019-08-29 23:34 ` Ira Weiny
2019-09-04 12:52 ` Jeff Layton
2019-09-04 23:12 ` John Hubbard
2019-08-09 22:58 ` [RFC PATCH v2 03/19] mm/gup: Pass flags down to __gup_device_huge* calls ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 04/19] mm/gup: Ensure F_LAYOUT lease is held prior to GUP'ing pages ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 05/19] fs/ext4: Teach ext4 to break layout leases ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 06/19] fs/ext4: Teach dax_layout_busy_page() to operate on a sub-range ira.weiny
2019-08-23 15:18 ` Vivek Goyal
2019-08-29 18:52 ` Ira Weiny
2019-08-09 22:58 ` [RFC PATCH v2 07/19] fs/xfs: Teach xfs to use new dax_layout_busy_page() ira.weiny
2019-08-09 23:30 ` Dave Chinner
2019-08-12 18:05 ` Ira Weiny
2019-08-14 8:04 ` Dave Chinner
2019-08-09 22:58 ` [RFC PATCH v2 08/19] fs/xfs: Fail truncate if page lease can't be broken ira.weiny
2019-08-09 23:22 ` Dave Chinner
2019-08-12 18:08 ` Ira Weiny
2019-08-09 22:58 ` [RFC PATCH v2 09/19] mm/gup: Introduce vaddr_pin structure ira.weiny
2019-08-10 0:06 ` John Hubbard
2019-08-09 22:58 ` [RFC PATCH v2 10/19] mm/gup: Pass a NULL vaddr_pin through GUP fast ira.weiny
2019-08-10 0:06 ` John Hubbard
2019-08-09 22:58 ` [RFC PATCH v2 11/19] mm/gup: Pass follow_page_context further down the call stack ira.weiny
2019-08-10 0:18 ` John Hubbard
2019-08-12 19:01 ` Ira Weiny
2019-08-09 22:58 ` [RFC PATCH v2 12/19] mm/gup: Prep put_user_pages() to take an vaddr_pin struct ira.weiny
2019-08-10 0:30 ` John Hubbard
2019-08-12 20:46 ` Ira Weiny
2019-08-09 22:58 ` [RFC PATCH v2 13/19] {mm,file}: Add file_pins objects ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 14/19] fs/locks: Associate file pins while performing GUP ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 15/19] mm/gup: Introduce vaddr_pin_pages() ira.weiny
2019-08-10 0:09 ` John Hubbard
2019-08-12 21:00 ` Ira Weiny
2019-08-12 21:20 ` John Hubbard
2019-08-11 23:07 ` John Hubbard
2019-08-12 21:01 ` Ira Weiny
2019-08-12 12:28 ` Jason Gunthorpe
2019-08-12 21:48 ` Ira Weiny
2019-08-13 11:47 ` Jason Gunthorpe
2019-08-13 17:46 ` Ira Weiny
2019-08-13 17:56 ` John Hubbard
2019-08-09 22:58 ` [RFC PATCH v2 16/19] RDMA/uverbs: Add back pointer to system file object ira.weiny
2019-08-12 13:00 ` Jason Gunthorpe
2019-08-12 17:28 ` Ira Weiny
2019-08-12 17:56 ` Jason Gunthorpe
2019-08-12 21:15 ` Ira Weiny
2019-08-13 11:48 ` Jason Gunthorpe
2019-08-13 17:41 ` Ira Weiny
2019-08-13 18:00 ` Jason Gunthorpe
2019-08-13 20:38 ` Ira Weiny
2019-08-14 12:23 ` Jason Gunthorpe
2019-08-14 17:50 ` Ira Weiny
2019-08-14 18:15 ` Jason Gunthorpe
2019-09-04 22:25 ` Ira Weiny
2019-08-09 22:58 ` [RFC PATCH v2 17/19] RDMA/umem: Convert to vaddr_[pin|unpin]* operations ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 18/19] {mm,procfs}: Add display file_pins proc ira.weiny
2019-08-09 22:58 ` [RFC PATCH v2 19/19] mm/gup: Remove FOLL_LONGTERM DAX exclusion ira.weiny
2019-08-14 10:17 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Jan Kara
2019-08-14 18:08 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) Ira Weiny
2019-08-15 13:05 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Jan Kara
2019-08-16 19:05 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) Ira Weiny
2019-08-16 23:20 ` Ira Weiny
2019-08-19 6:36 ` Jan Kara
2019-08-17 2:26 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Dave Chinner
2019-08-19 6:34 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) Jan Kara
2019-08-19 9:24 ` Dave Chinner
2019-08-19 12:38 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Jason Gunthorpe
2019-08-19 21:53 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) Ira Weiny
2019-08-20 1:12 ` Dave Chinner
2019-08-20 11:55 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Jason Gunthorpe
2019-08-21 18:02 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) Ira Weiny
2019-08-21 18:13 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Jason Gunthorpe
2019-08-21 18:22 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) John Hubbard
2019-08-21 18:57 ` Ira Weiny
2019-08-21 19:06 ` Ira Weiny
2019-08-21 19:48 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Jason Gunthorpe
2019-08-21 20:44 ` Ira Weiny
2019-08-21 23:49 ` Jason Gunthorpe
2019-08-23 3:23 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) Dave Chinner
2019-08-23 12:04 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Jason Gunthorpe
2019-08-24 0:11 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) Dave Chinner
2019-08-24 5:08 ` Ira Weiny
2019-08-26 5:55 ` Dave Chinner
2019-08-29 2:02 ` Ira Weiny
2019-08-29 3:27 ` John Hubbard
2019-08-29 16:16 ` Ira Weiny
2019-09-02 22:26 ` Dave Chinner
2019-09-04 16:54 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Ira Weiny
2019-08-25 19:39 ` Jason Gunthorpe
2019-08-24 4:49 ` Ira Weiny
2019-08-25 19:40 ` Jason Gunthorpe
2019-08-23 0:59 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) Dave Chinner
2019-08-23 17:15 ` Ira Weiny
2019-08-24 0:18 ` Dave Chinner
2019-08-20 0:05 ` John Hubbard
2019-08-20 1:20 ` Dave Chinner
2019-08-20 3:09 ` John Hubbard
2019-08-20 3:36 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-) Dave Chinner
2019-08-21 18:43 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) John Hubbard
2019-08-21 19:09 ` Ira Weiny
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