From: Ira Weiny <ira.weiny@intel.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: "Jan Kara" <jack@suse.cz>,
"Dan Williams" <dan.j.williams@intel.com>,
"Theodore Ts'o" <tytso@mit.edu>,
"Jeff Layton" <jlayton@kernel.org>,
"Dave Chinner" <david@fromorbit.com>,
"Matthew Wilcox" <willy@infradead.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
Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal
Date: Thu, 6 Jun 2019 15:22:28 -0700 [thread overview]
Message-ID: <20190606222228.GB11698@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20190606195114.GA30714@ziepe.ca>
On Thu, Jun 06, 2019 at 04:51:15PM -0300, Jason Gunthorpe wrote:
> On Thu, Jun 06, 2019 at 12:42:03PM +0200, Jan Kara wrote:
>
> > So I'd like to actually mandate that you *must* hold the file lease until
> > you unpin all pages in the given range (not just that you have an option to
> > hold a lease). And I believe the kernel should actually enforce this. That
> > way we maintain a sane state that if someone uses a physical location of
> > logical file offset on disk, he has a layout lease. Also once this is done,
> > sysadmin has a reasonably easy way to discover run-away RDMA application
> > and kill it if he wishes so.
> >
> > The question is on how to exactly enforce that lease is taken until all
> > pages are unpinned. I belive it could be done by tracking number of
> > long-term pinned pages within a lease. Gup_longterm could easily increment
> > the count when verifying the lease exists, gup_longterm users will somehow
> > need to propagate corresponding 'filp' (struct file pointer) to
> > put_user_pages_longterm() callsites so that they can look up appropriate
> > lease to drop reference - probably I'd just transition all gup_longterm()
> > users to a saner API similar to the one we have in mm/frame_vector.c where
> > we don't hand out page pointers but an encapsulating structure that does
> > all the necessary tracking. Removing a lease would need to block until all
> > pins are released - this is probably the most hairy part since we need to
> > handle a case if application just closes the file descriptor which
> > would
>
> I think if you are going to do this then the 'struct filp' that
> represents the lease should be held in the kernel (ie inside the RDMA
> umem) until the kernel is done with it.
Yea there seems merit to this. I'm still not resolving how this helps track
who has the pin across a fork.
>
> Actually does someone have a pointer to this userspace lease API, I'm
> not at all familiar with it, thanks
man fcntl
search for SETLEASE
But I had to add the F_LAYOUT lease type. (Personally I'm for calling it
F_LONGTERM at this point. I don't think LAYOUT is compatible with what we are
proposing here.)
Anyway, yea would be a libc change at lease for man page etc... But again I
want to get some buy in before going through all that.
>
> And yes, a better output format from GUP would be great..
>
> > Maybe we could block only on explicit lease unlock and just drop the layout
> > lease on file close and if there are still pinned pages, send SIGKILL to an
> > application as a reminder it did something stupid...
>
> Which process would you SIGKILL? At least for the rdma case a FD is
> holding the GUP, so to do the put_user_pages() the kernel needs to
> close the FD. I guess it would have to kill every process that has the
> FD open? Seems complicated...
Tending to agree... But I'm still not opposed to killing bad actors... ;-)
NOTE: Jason I think you need to be more clear about the FD you are speaking of.
I believe you mean the FD which refers to the RMDA context. That is what I
called it in my other email.
Ira
>
> Regards,
> Jason
next prev parent reply other threads:[~2019-06-06 22:21 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 [this message]
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
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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