+ mm-khugepaged-skip-dax-vma.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: khugepaged: skip DAX vma
has been added to the -mm tree.  Its filename is
     mm-khugepaged-skip-dax-vma.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-khugepaged-skip-dax-vma.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-khugepaged-skip-dax-vma.patch

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------------------------------------------------------
From: Yang Shi <shy828301@gmail.com>
Subject: mm: khugepaged: skip DAX vma

The DAX vma may be seen by khugepaged when the mm has other khugepaged
suitable vmas.  So khugepaged may try to collapse THP for DAX vma, but it
will fail due to page sanity check, for example, page is not on LRU.

So it is not harmful, but it is definitely pointless to run khugepaged
against DAX vma, so skip it in early check.

Link: https://lkml.kernel.org/r/20220404200250.321455-4-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Song Liu <song@kernel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/khugepaged.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/mm/khugepaged.c~mm-khugepaged-skip-dax-vma
+++ a/mm/khugepaged.c
@@ -447,6 +447,10 @@ static bool hugepage_vma_check(struct vm
 	if (vm_flags & VM_NO_KHUGEPAGED)
 		return false;
 
+	/* Don't run khugepaged against DAX vma */
+	if (vma_is_dax(vma))
+		return false;
+
 	if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) -
 				vma->vm_pgoff, HPAGE_PMD_NR))
 		return false;
_

Patches currently in -mm which might be from shy828301@gmail.com are

sched-coredumph-clarify-the-use-of-mmf_vm_hugepage.patch
mm-khugepaged-remove-redundant-check-for-vm_no_khugepaged.patch
mm-khugepaged-skip-dax-vma.patch
mm-thp-only-regular-file-could-be-thp-eligible.patch
mm-khugepaged-make-khugepaged_enter-void-function.patch
mm-khugepaged-move-some-khugepaged_-functions-to-khugepagedc.patch
mm-khugepaged-introduce-khugepaged_enter_vma-helper.patch
mm-mmap-register-suitable-readonly-file-vmas-for-khugepaged.patch