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From: Pankaj Gupta <pagupta@redhat.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>, KVM list <kvm@vger.kernel.org>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>, david <david@fromorbit.com>,
	Qemu Developers <qemu-devel@nongnu.org>,
	virtualization@lists.linux-foundation.org,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Ross Zwisler <zwisler@kernel.org>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Dave Jiang <dave.jiang@intel.com>,
	jstaron@google.com, linux-nvdimm <linux-nvdimm@lists.01.org>,
	Vishal L Verma <vishal.l.verma@intel.com>,
	David Hildenbrand <david@redhat.com>,
	Matthew Wilcox <willy@infradead.org>,
	Christoph Hellwig <hch@infradead.org>,
	Linux ACPI <linux-acpi@vger.kernel.org>,
	jmoyer <jmoyer@redhat.com>,
	linux-ext4 <linux-ext4@vger.kernel.org>,
	Len Brown <lenb@kernel.org>, Adam Borowski <kilobyte@angband.pl>,
	Rik van Riel <riel@surriel.com>,
	yuval shaia <yuval.shaia@oracle.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Igor Mammedov <imammedo@redhat.com>,
	lcapitulino@redhat.com, Kevin Wolf <kwolf@redhat.com>,
	Nitesh Narayan Lal <nilal@redhat.com>,
	Theodore Ts'o <tytso@mit.edu>,
	Xiao Guangrong <xiaoguangrong.eric@gmail.com>,
	cohuck@redhat.com, "Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-xfs <linux-xfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"Darrick J. Wong" <darrick.wong@oracle.com>
Subject: Re: [Qemu-devel] [PATCH v8 3/6] libnvdimm: add dax_dev sync flag
Date: Tue, 14 May 2019 01:27:17 -0400 (EDT)	[thread overview]
Message-ID: <676644679.28490825.1557811637861.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <CAPcyv4genJtCt6dp6N07_6RfPTwC6xXMhLp-dr0GWQy5q52YoA@mail.gmail.com>


> >
> >
> > Hi Dan,
> >
> > While testing device mapper with DAX, I faced a bug with the commit:
> >
> > commit ad428cdb525a97d15c0349fdc80f3d58befb50df
> > Author: Dan Williams <dan.j.williams@intel.com>
> > Date:   Wed Feb 20 21:12:50 2019 -0800
> >
> > When I reverted the condition to old code[1] it worked for me. I
> > am thinking when we map two different devices (e.g with device mapper),
> > will
> > start & end pfn still point to same pgmap? Or there is something else which
> > I am missing here.
> >
> > Note: I tested only EXT4.
> >
> > [1]
> >
> > -               if (pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX)
> > +               end_pgmap = get_dev_pagemap(pfn_t_to_pfn(end_pfn), NULL);
> > +               if (pgmap && pgmap == end_pgmap && pgmap->type ==
> > MEMORY_DEVICE_FS_DAX
> > +                               && pfn_t_to_page(pfn)->pgmap == pgmap
> > +                               && pfn_t_to_page(end_pfn)->pgmap == pgmap
> > +                               && pfn_t_to_pfn(pfn) ==
> > PHYS_PFN(__pa(kaddr))
> > +                               && pfn_t_to_pfn(end_pfn) ==
> > PHYS_PFN(__pa(end_kaddr)))
> 
> Ugh, yes, device-mapper continues to be an awkward fit for dax (or
> vice versa). We would either need a way to have a multi-level pfn to
> pagemap lookup for composite devices, or a way to discern that even
> though the pagemap is different that the result is still valid / not
> an indication that we have leaked into an unassociated address range.
> Perhaps a per-daxdev callback for ->dax_supported() so that
> device-mapper internals can be used for this validation.

Yes, Will look at it.

> 
> We need to get that fixed up, but I don't see it as a blocker /
> pre-requisite for virtio-pmem.

Agree. Will send virtio-pmem patch series.

Thank you,
Pankaj
> 
> 

  reply	other threads:[~2019-05-14  5:27 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-10 15:51 [PATCH v8 0/6] virtio pmem driver Pankaj Gupta
2019-05-10 15:51 ` [PATCH v8 1/6] libnvdimm: nd_region flush callback support Pankaj Gupta
2019-05-10 15:51 ` [PATCH v8 2/6] virtio-pmem: Add virtio pmem driver Pankaj Gupta
2019-05-12 16:51   ` Michael S. Tsirkin
2019-05-13  4:43     ` [Qemu-devel] " Pankaj Gupta
2019-05-14  8:19   ` David Hildenbrand
2019-05-14  9:27     ` Pankaj Gupta
2019-05-14  9:34       ` David Hildenbrand
2019-05-14  9:47         ` Pankaj Gupta
2019-05-14  9:57           ` David Hildenbrand
2019-05-14 10:02             ` Pankaj Gupta
2019-05-10 15:51 ` [PATCH v8 3/6] libnvdimm: add dax_dev sync flag Pankaj Gupta
2019-05-10 20:14   ` Dan Williams
2019-05-11  0:45     ` Pankaj Gupta
2019-05-11  0:59       ` Dan Williams
2019-05-11  1:23         ` [Qemu-devel] " Pankaj Gupta
2019-05-13 17:32           ` Pankaj Gupta
2019-05-13 17:52             ` Dan Williams
2019-05-14  5:27               ` Pankaj Gupta [this message]
2019-05-10 15:52 ` [PATCH v8 4/6] dax: check synchronous mapping is supported Pankaj Gupta
2019-05-10 15:52 ` [PATCH v8 5/6] ext4: disable map_sync for async flush Pankaj Gupta
2019-05-10 15:52 ` [PATCH v8 6/6] xfs: " Pankaj Gupta
2019-05-10 16:30 ` [PATCH v8 0/6] virtio pmem driver Michael S. Tsirkin
2019-05-10 20:15 ` Dan Williams
2019-05-10 23:33   ` Pankaj Gupta
2019-05-12 16:52     ` Michael S. Tsirkin

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