Patch series "vhost, docs: convert to pin_user_pages(), new "case 5""
It recently became clear to me that there are some get_user_pages*()
callers that don't fit neatly into any of the four cases that are so far
listed in pin_user_pages.rst. vhost.c is one of those.
Add a Case 5 to the documentation, and refer to that when converting
vhost.c.
Thanks to Jan Kara for helping me (again) in understanding the
interaction between get_user_pages() and page writeback [1].
This is based on today's mmotm, which has a nearby patch to
pin_user_pages.rst that rewords cases 3 and 4.
Note that I have only compile-tested the vhost.c patch, although that
does also include cross-compiling for a few other arches. Any run-time
testing would be greatly appreciated.
[1] https://lore.kernel.org/r/20200529070343.GL14550@quack2.suse.cz
This patch (of 2):
There are four cases listed in pin_user_pages.rst. These are intended
to help developers figure out whether to use get_user_pages*(), or
pin_user_pages*(). However, the four cases do not cover all the
situations. For example, drivers/vhost/vhost.c has a "pin, write to
page, set page dirty, unpin" case.
Add a fifth case, to help explain that there is a general pattern that
requires pin_user_pages*() API calls.
[jhubbard@nvidia.com: v2]
Link: http://lkml.kernel.org/r/20200601052633.853874-2-jhubbard@nvidia.com
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: "Michael S . Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Link: http://lkml.kernel.org/r/20200529234309.484480-1-jhubbard@nvidia.com
Link: http://lkml.kernel.org/r/20200529234309.484480-2-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
eaf4d22a9e
