Re: [PATCH 19/19] Documentation/vm: add pin_user_pages.rst
From: John Hubbard <jhubbard@nvidia.com>
Date: 2019-10-31 23:53:49
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bpf, dri-devel, kvm, linux-block, linux-doc, linux-fsdevel, linux-kselftest, linux-media, linux-mm, linux-rdma, linuxppc-dev, lkml
On 10/31/19 4:49 PM, Ira Weiny wrote:
On Wed, Oct 30, 2019 at 03:49:30PM -0700, John Hubbard wrote:quoted
Document the new pin_user_pages() and related calls and behavior. Thanks to Jan Kara and Vlastimil Babka for explaining the 4 cases in this documentation. (I've reworded it and expanded on it slightly.)As I said before I think this may be better in a previous patch where you reference it.
Yes, I'll merge this in with patch #5 ("mm/gup: introduce pin_user_pages*()
and FOLL_PIN").
...quoted
+TODO: There is also a special case when the pages are DAX pages: in addition to +the above flags, the caller needs something like a layout lease on the +associated file. This is yet to be implemented. When it is implemented, it's +expected that the lease will be a prerequisite to setting FOLL_LONGTERM.For now we probably want to leave this note out until we figure out how this is going to work. Best to say something like: Some pages, such as DAX pages, can't be pinned with longterm pins and will fail.
OK, that is better, I'll use that instead of the "TODO". thanks, John Hubbard NVIDIA