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From: Alex Williamson <alex.williamson@redhat.com>
To: John Hubbard <jhubbard@nvidia.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Dave Chinner" <david@fromorbit.com>,
	"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	"Michal Hocko" <mhocko@suse.com>,
	"Mike Kravetz" <mike.kravetz@oracle.com>,
	"Shuah Khan" <shuah@kernel.org>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Matthew Wilcox" <willy@infradead.org>,
	linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-rdma@vger.kernel.org,
	linux-mm@kvack.org,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [regression] Re: [PATCH v6 06/12] mm/gup: track FOLL_PIN pages
Date: Fri, 24 Apr 2020 14:15:48 -0600	[thread overview]
Message-ID: <20200424141548.5afdd2bb@w520.home> (raw)
In-Reply-To: <5b901542-d949-8d7e-89c7-f8d5ee20f6e9@nvidia.com>

On Fri, 24 Apr 2020 12:20:03 -0700
John Hubbard <jhubbard@nvidia.com> wrote:

> On 2020-04-24 11:18, Alex Williamson wrote:
> ...
> > Hi John,
> > 
> > I'm seeing a regression bisected back to this commit (3faa52c03f44
> > mm/gup: track FOLL_PIN pages).  I've attached some vfio-pci test code
> > that reproduces this by mmap'ing a page of MMIO space of a device and
> > then tries to map that through the IOMMU, so this should be attempting
> > a gup/pin of a PFNMAP page.  Previously this failed gracefully (-EFAULT),
> > but now results in:  
> 
> 
> Hi Alex,
> 
> Thanks for this report, and especially for source code to test it, 
> seeing as how I can't immediately spot the problem just from the crash
> data so far.  I'll get set up and attempt a repro.
> 
> Actually this looks like it should be relatively easier than the usual 
> sort of "oops, we leaked a pin_user_pages() or unpin_user_pages() call,
> good luck finding which one" report that I fear the most. :) This one 
> looks more like a crash that happens directly, when calling into the 
> pin_user_pages_remote() code. Which should be a lot easier to solve...
> 
> btw, if you are set up for it, it would be nice to know what source file 
> and line number corresponds to the RIP (get_pfnblock_flags_mask+0x22) 
> below. But if not, no problem, because I've likely got to do the repro 
> in any case.

Hey John,

TBH I'm feeling a lot less confident about this bisect.  This was
readily reproducible to me on a clean tree a bit ago, but now it
eludes me.  Let me go back and figure out what's going on before you
spend any more time on it.  Thanks,

Alex


  reply	other threads:[~2020-04-24 20:16 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11  0:15 [PATCH v6 00/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-02-11  0:15 ` [PATCH v6 01/12] mm/gup: split get_user_pages_remote() into two routines John Hubbard
2020-02-11  0:15 ` [PATCH v6 02/12] mm/gup: pass a flags arg to __gup_device_* functions John Hubbard
2020-02-11  0:15 ` [PATCH v6 03/12] mm: introduce page_ref_sub_return() John Hubbard
2020-02-11  0:15 ` [PATCH v6 04/12] mm/gup: pass gup flags to two more routines John Hubbard
2020-02-11  0:15 ` [PATCH v6 05/12] mm/gup: require FOLL_GET for get_user_pages_fast() John Hubbard
2020-02-11  0:15 ` [PATCH v6 06/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-04-24 18:18   ` [regression] " Alex Williamson
2020-04-24 19:20     ` John Hubbard
2020-04-24 20:15       ` Alex Williamson [this message]
2020-04-24 22:58         ` John Hubbard
2020-04-28 16:54           ` [regression?] " Alex Williamson
2020-04-28 17:49             ` Jason Gunthorpe
2020-04-28 19:07               ` Alex Williamson
2020-04-28 19:22                 ` Jason Gunthorpe
2020-04-28 20:12                   ` Alex Williamson
2020-04-29  0:29                     ` Jason Gunthorpe
2020-04-29 19:56                       ` Alex Williamson
2020-04-29 23:03                         ` Jason Gunthorpe
2020-02-11  0:15 ` [PATCH v6 07/12] mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages John Hubbard
2020-02-11  0:15 ` [PATCH v6 08/12] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting John Hubbard
2020-02-12  9:17   ` Jan Kara
2020-02-11  0:15 ` [PATCH v6 09/12] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2020-02-11  0:15 ` [PATCH v6 10/12] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard
2020-02-11  0:15 ` [PATCH v6 11/12] mm: Improve dump_page() for compound pages John Hubbard
2020-02-11  0:15 ` [PATCH v6 12/12] mm: dump_page(): additional diagnostics for huge pinned pages John Hubbard
2020-02-11 13:21   ` Kirill A. Shutemov
2020-02-12  2:10     ` John Hubbard

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