From: Christoph Hellwig <hch@infradead.org>
To: Martin Oliveira <martin.oliveira@eideticom.com>
Cc: linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Artemy Kovalyov <artemyko@nvidia.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jason Gunthorpe <jgg@ziepe.ca>, Leon Romanovsky <leon@kernel.org>,
Logan Gunthorpe <logang@deltatee.com>,
Michael Guralnik <michaelgur@nvidia.com>,
Mike Marciniszyn <mike.marciniszyn@intel.com>,
Shiraz Saleem <shiraz.saleem@intel.com>,
Tejun Heo <tj@kernel.org>, John Hubbard <jhubbard@nvidia.com>,
Dan Williams <dan.j.williams@intel.com>,
David Sloan <david.sloan@eideticom.com>
Subject: Re: [PATCH v5 3/4] mm/gup: allow FOLL_LONGTERM & FOLL_PCI_P2PDMA
Date: Sun, 11 Aug 2024 23:39:22 -0700 [thread overview]
Message-ID: <ZrmuGrDaJTZFrKrc@infradead.org> (raw)
In-Reply-To: <20240808183340.483468-4-martin.oliveira@eideticom.com>
On Thu, Aug 08, 2024 at 12:33:39PM -0600, Martin Oliveira wrote:
> This check existed originally due to concerns that P2PDMA needed to copy
> fsdax until pgmap refcounts were fixed (see [1]).
>
> The P2PDMA infrastructure will only call unmap_mapping_range() when the
> underlying device is unbound, and immediately after unmapping it waits
> for the reference of all ZONE_DEVICE pages to be released before
> continuing. This does not allow for a page to be reused and no user
> access fault is therefore possible. It does not have the same problem as
> fsdax.
>
> The one minor concern with FOLL_LONGTERM pins is they will block device
> unbind until userspace releases them all.
This is unfortunately not really minor unless we have a well documented
way to force this :(
next prev parent reply other threads:[~2024-08-12 6:39 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-08 18:33 [PATCH v5 0/4] Enable P2PDMA in Userspace RDMA Martin Oliveira
2024-08-08 18:33 ` [PATCH v5 1/4] kernfs: add a WARN_ON_ONCE if ->close is set Martin Oliveira
2024-08-09 5:37 ` Greg Kroah-Hartman
2024-08-09 15:41 ` Martin Oliveira
2024-08-11 8:31 ` Greg Kroah-Hartman
2024-08-12 6:38 ` Christoph Hellwig
2024-08-12 6:38 ` Christoph Hellwig
2024-08-08 18:33 ` [PATCH v5 2/4] kernfs: remove page_mkwrite() from vm_operations_struct Martin Oliveira
2024-08-12 6:38 ` Christoph Hellwig
2024-08-08 18:33 ` [PATCH v5 3/4] mm/gup: allow FOLL_LONGTERM & FOLL_PCI_P2PDMA Martin Oliveira
2024-08-12 6:39 ` Christoph Hellwig [this message]
2024-08-12 23:12 ` Jason Gunthorpe
2024-08-13 5:41 ` Christoph Hellwig
2024-08-13 16:05 ` Jason Gunthorpe
2024-08-13 17:03 ` Dan Williams
2024-08-14 0:02 ` Jason Gunthorpe
2024-08-14 4:26 ` Christoph Hellwig
2024-08-15 16:38 ` Jason Gunthorpe
2024-08-08 18:33 ` [PATCH v5 4/4] RDMA/umem: add support for P2P RDMA Martin Oliveira
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