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Aneesh Kumar K.V authored
This patch updates get_user_pages_longterm to migrate pages allocated
out of CMA region.  This makes sure that we don't keep non-movable pages
(due to page reference count) in the CMA area.

This will be used by ppc64 in a later patch to avoid pinning pages in
the CMA region.  ppc64 uses CMA region for allocation of the hardware
page table (hash page table) and not able to migrate pages out of CMA
region results in page table allocation failures.

One case where we hit this easy is when a guest using a VFIO passthrough
device.  VFIO locks all the guest's memory and if the guest memory is
backed by CMA region, it becomes unmovable resulting in fragmenting the
CMA and possibly preventing other guests from allocation a large enough
hash page table.

NOTE: We allocate the new page without using __GFP_THISNODE

Link: http://lkml.kernel.org/r/20190114095438.32470-3-aneesh.kumar@linux.ibm.com


Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
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Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.