From: Jason Gunthorpe <jgg@ziepe.ca>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
linux-mm@kvack.org, "Christoph Hellwig" <hch@lst.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Dan Williams" <dan.j.williams@intel.com>,
"Christian König" <christian.koenig@amd.com>,
"John Hubbard" <jhubbard@nvidia.com>,
"Don Dutile" <ddutile@redhat.com>,
"Matthew Wilcox" <willy@infradead.org>,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Minturn Dave B" <dave.b.minturn@intel.com>,
"Jason Ekstrand" <jason@jlekstrand.net>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Xiong Jianxin" <jianxin.xiong@intel.com>,
"Bjorn Helgaas" <helgaas@kernel.org>,
"Ira Weiny" <ira.weiny@intel.com>,
"Robin Murphy" <robin.murphy@arm.com>,
"Martin Oliveira" <martin.oliveira@eideticom.com>,
"Chaitanya Kulkarni" <ckulkarnilinux@gmail.com>,
"Ralph Campbell" <rcampbell@nvidia.com>,
"Stephen Bates" <sbates@raithlin.com>
Subject: Re: [PATCH v10 1/8] mm: introduce FOLL_PCI_P2PDMA to gate getting PCI P2PDMA pages
Date: Fri, 23 Sep 2022 20:07:04 -0300 [thread overview]
Message-ID: <Yy48GPMdQS/pzNSa@ziepe.ca> (raw)
In-Reply-To: <3840c1c6-3a5c-2286-e577-949f0d4ea7a6@deltatee.com>
On Fri, Sep 23, 2022 at 05:01:26PM -0600, Logan Gunthorpe wrote:
>
>
>
> On 2022-09-23 16:58, Jason Gunthorpe wrote:
> > On Fri, Sep 23, 2022 at 02:11:03PM -0600, Logan Gunthorpe wrote:
> >>
> >>
> >> On 2022-09-23 13:53, Jason Gunthorpe wrote:
> >>> On Fri, Sep 23, 2022 at 01:08:31PM -0600, Logan Gunthorpe wrote:
> >>> I'm encouraging Dan to work on better infrastructure in pgmap core
> >>> because every pgmap implementation has this issue currently.
> >>>
> >>> For that reason it is probably not so relavent to this series.
> >>>
> >>> Perhaps just clarify in the commit message that the FOLL_LONGTERM
> >>> restriction is to copy DAX until the pgmap page refcounts are fixed.
> >>
> >> Ok, I'll add that note.
> >>
> >> Per the fix for the try_grab_page(), to me it doesn't fit well in
> >> try_grab_page() without doing a bunch of cleanup to change the
> >> error handling, and the same would have to be added to try_grab_folio().
> >> So I think it's better to leave it where it was, but move it below the
> >> respective grab calls. Does the incremental patch below look correct?
> >
> > Oh? I was thinking of just a very simple thing:
>
> Really would like it to return -EREMOTEIO instead of -ENOMEM as that's the
> error used for bad P2PDMA page everywhere.
I'd rather not see GUP made more fragile just for that..
> Plus the concern that some of the callsites of try_grab_page() might not have
> a get or a pin and thus it's not safe which was the whole point of the change
> anyway.
try_grab_page() calls folio_ref_inc(), that is only legal if it knows
the page is already a valid pointer under the PTLs, so it is safe to
check the pgmap as well.
Jason
next prev parent reply other threads:[~2022-09-23 23:07 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-22 16:39 [PATCH v10 0/8] Userspace P2PDMA with O_DIRECT NVMe devices Logan Gunthorpe
2022-09-22 16:39 ` [PATCH v10 1/8] mm: introduce FOLL_PCI_P2PDMA to gate getting PCI P2PDMA pages Logan Gunthorpe
2022-09-23 18:13 ` Jason Gunthorpe
2022-09-23 19:08 ` Logan Gunthorpe
2022-09-23 19:53 ` Jason Gunthorpe
2022-09-23 20:11 ` Logan Gunthorpe
2022-09-23 22:58 ` Jason Gunthorpe
2022-09-23 23:01 ` Logan Gunthorpe
2022-09-23 23:07 ` Jason Gunthorpe [this message]
2022-09-23 23:14 ` Logan Gunthorpe
2022-09-23 23:21 ` Jason Gunthorpe
2022-09-23 23:35 ` Logan Gunthorpe
2022-09-23 23:51 ` Logan Gunthorpe
2022-09-26 22:57 ` Jason Gunthorpe
2022-09-28 21:38 ` Logan Gunthorpe
2022-09-22 16:39 ` [PATCH v10 2/8] iov_iter: introduce iov_iter_get_pages_[alloc_]flags() Logan Gunthorpe
2022-09-22 16:39 ` [PATCH v10 3/8] block: add check when merging zone device pages Logan Gunthorpe
2022-09-22 16:39 ` [PATCH v10 4/8] lib/scatterlist: " Logan Gunthorpe
2022-09-22 16:39 ` [PATCH v10 5/8] block: set FOLL_PCI_P2PDMA in __bio_iov_iter_get_pages() Logan Gunthorpe
2022-09-22 16:39 ` [PATCH v10 6/8] block: set FOLL_PCI_P2PDMA in bio_map_user_iov() Logan Gunthorpe
2022-09-22 16:39 ` [PATCH v10 7/8] PCI/P2PDMA: Allow userspace VMA allocations through sysfs Logan Gunthorpe
2022-09-22 18:27 ` Bjorn Helgaas
2022-09-23 8:15 ` Greg Kroah-Hartman
2022-09-22 16:39 ` [PATCH v10 8/8] ABI: sysfs-bus-pci: add documentation for p2pmem allocate Logan Gunthorpe
2022-09-23 8:15 ` Greg Kroah-Hartman
2022-09-23 6:01 ` [PATCH v10 0/8] Userspace P2PDMA with O_DIRECT NVMe devices Christoph Hellwig
2022-09-23 15:25 ` Logan Gunthorpe
2022-09-23 8:16 ` Greg Kroah-Hartman
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