Commit 0ccf7f16 authored Aug 11, 2022 by Peter Xu Committed by Andrew Morton Sep 26, 2022

mm/thp: carry over dirty bit when thp splits on pmd

Carry over the dirty bit from pmd to pte when a huge pmd splits.  It
shouldn't be a correctness issue since when pmd_dirty() we'll have the
page marked dirty anyway, however having dirty bit carried over helps the
next initial writes of split ptes on some archs like x86.

Link: https://lkml.kernel.org/r/20220811161331.37055-5-peterx@redhat.com


Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Huang Ying <ying.huang@intel.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 0d206b5d

mm/huge_memory.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -2037,7 +2037,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct vma, pmd_t pmd,
		pgtable_t pgtable;
		pmd_t old_pmd, _pmd;
		bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
		bool anon_exclusive = false;
		bool anon_exclusive = false, dirty = false;
		unsigned long addr;
		int i;

		@@ -2126,8 +2126,10 @@ static void __split_huge_pmd_locked(struct vm_area_struct vma, pmd_t pmd,
		uffd_wp = pmd_swp_uffd_wp(old_pmd);
		} else {
		page = pmd_page(old_pmd);
		if (pmd_dirty(old_pmd))
		if (pmd_dirty(old_pmd)) {
		dirty = true;
		SetPageDirty(page);
		}
		write = pmd_write(old_pmd);
		young = pmd_young(old_pmd);
		soft_dirty = pmd_soft_dirty(old_pmd);
		@@ -2195,6 +2197,9 @@ static void __split_huge_pmd_locked(struct vm_area_struct vma, pmd_t pmd,
		entry = pte_wrprotect(entry);
		if (!young)
		entry = pte_mkold(entry);
		/* NOTE: this may set soft-dirty too on some archs */
		if (dirty)
		entry = pte_mkdirty(entry);
		if (soft_dirty)
		entry = pte_mksoft_dirty(entry);
		if (uffd_wp)