From: John Hubbard <jhubbard@nvidia.com>
To: Ira Weiny <ira.weiny@intel.com>, Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>, Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Dan Williams <dan.j.williams@intel.com>,
Matthew Wilcox <willy@infradead.org>,
Theodore Ts'o <tytso@mit.edu>, Michal Hocko <mhocko@suse.com>,
<linux-xfs@vger.kernel.org>, <linux-rdma@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
<linux-nvdimm@lists.01.org>, <linux-ext4@vger.kernel.org>,
<linux-mm@kvack.org>
Subject: Re: [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ;-)
Date: Wed, 28 Aug 2019 20:27:23 -0700 [thread overview]
Message-ID: <3e5c5053-a74a-509c-660c-a6075ed87f11@nvidia.com> (raw)
In-Reply-To: <20190829020230.GA18249@iweiny-DESK2.sc.intel.com>
On 8/28/19 7:02 PM, Ira Weiny wrote:
> On Mon, Aug 26, 2019 at 03:55:10PM +1000, Dave Chinner wrote:
>> On Fri, Aug 23, 2019 at 10:08:36PM -0700, Ira Weiny wrote:
>>> On Sat, Aug 24, 2019 at 10:11:24AM +1000, Dave Chinner wrote:
>>>> On Fri, Aug 23, 2019 at 09:04:29AM -0300, Jason Gunthorpe wrote:
...
>>
>> Sure, that part works because the struct file is passed. It doesn't
>> end up with the same fd number in the other process, though.
>>
>> The issue is that layout leases need to notify userspace when they
>> are broken by the kernel, so a lease stores the owner pid/tid in the
>> file->f_owner field via __f_setown(). It also keeps a struct fasync
>> attached to the file_lock that records the fd that the lease was
>> created on. When a signal needs to be sent to userspace for that
>> lease, we call kill_fasync() and that walks the list of fasync
>> structures on the lease and calls:
>>
>> send_sigio(fown, fa->fa_fd, band);
>>
>> And it does for every fasync struct attached to a lease. Yes, a
>> lease can track multiple fds, but it can only track them in a single
>> process context. The moment the struct file is shared with another
>> process, the lease is no longer capable of sending notifications to
>> all the lease holders.
>>
>> Yes, you can change the owning process via F_SETOWNER, but that's
>> still only a single process context, and you can't change the fd in
>> the fasync list. You can add new fd to an existing lease by calling
>> F_SETLEASE on the new fd, but you still only have a single process
>> owner context for signal delivery.
>>
>> As such, leases that require callbacks to userspace are currently
>> only valid within the process context the lease was taken in.
>
> But for long term pins we are not requiring callbacks.
>
Hi Ira,
If "require callbacks to userspace" means sending SIGIO, then actually
FOLL_LONGTERM *does* require those callbacks. Because we've been, so
far, equating FOLL_LONGTERM with the vaddr_pin struct and with a lease.
What am I missing here?
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2019-08-29 3:29 UTC|newest]
Thread overview: 110+ 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
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
2019-09-11 8:19 ` Jason Gunthorpe
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 ` Ira Weiny
2019-08-15 13:05 ` Jan Kara
2019-08-16 19:05 ` Ira Weiny
2019-08-16 23:20 ` [RFC PATCH v2 00/19] RDMA/FS DAX truncate proposal V1,000,002 ; -) 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 ` Jan Kara
2019-08-19 9:24 ` Dave Chinner
2019-08-19 12:38 ` Jason Gunthorpe
2019-08-19 21:53 ` Ira Weiny
2019-08-20 1:12 ` Dave Chinner
2019-08-20 11:55 ` Jason Gunthorpe
2019-08-21 18:02 ` Ira Weiny
2019-08-21 18:13 ` Jason Gunthorpe
2019-08-21 18:22 ` John Hubbard
2019-08-21 18:57 ` Ira Weiny
2019-08-21 19:06 ` Ira Weiny
2019-08-21 19:48 ` Jason Gunthorpe
2019-08-21 20:44 ` Ira Weiny
2019-08-21 23:49 ` Jason Gunthorpe
2019-08-23 3:23 ` Dave Chinner
2019-08-23 12:04 ` Jason Gunthorpe
2019-08-24 0:11 ` 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 [this message]
2019-08-29 16:16 ` Ira Weiny
2019-09-02 22:26 ` Dave Chinner
2019-09-04 16:54 ` 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 ` 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 ` Dave Chinner
2019-08-21 18:43 ` John Hubbard
2019-08-21 19:09 ` Ira Weiny
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