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This reverts commitc77c5cbafe. Since commitc77c5cbafe("mm: migrate: skip shared exec THP for NUMA balancing"), the NUMA balancing would skip shared exec transhuge page. But this enhancement is not suitable for transhuge page. Because it's required that page_mapcount() must be 1 due to no migration pte dance is done here. On the other hand, the shared exec transhuge page will leave the migrate_misplaced_page() with pte entry untouched and page locked. Thus pagefault for NUMA will be triggered again and deadlock occurs when we start waiting for the page lock held by ourselves. Yang Shi said: "Thanks for catching this. By relooking the code I think the other important reason for removing this is migrate_misplaced_transhuge_page() actually can't see shared exec file THP at all since page_lock_anon_vma_read() is called before and if page is not anonymous page it will just restore the PMD without migrating anything. The pages for private mapped file vma may be anonymous pages due to COW but they can't be THP so it won't trigger THP numa fault at all. I think this is why no bug was reported. I overlooked this in the first place." Link: https://lkml.kernel.org/r/20210325131524.48181-6-linmiaohe@huawei.com Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> Reviewed-by: Yang Shi <shy828301@gmail.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Rafael Aquini <aquini@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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.