[066/227] mm: thp: fix wrong cache flush in remove_migration_pmd()

Commit Message

Andrew Morton March 22, 2022, 9:41 p.m. UTC

From: Muchun Song <[e-mail]>
Subject: mm: thp: fix wrong cache flush in remove_migration_pmd()

Patch series "Fix some cache flush bugs", v5.

This series focuses on fixing cache maintenance.


This patch (of 7):

The flush_cache_range() is supposed to be justified only if the page is
already placed in process page table, and that is done right after
flush_cache_range().  So using this interface is wrong.  And there is no
need to invalite cache since it was non-present before in
remove_migration_pmd().  So just to remove it.

Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Muchun Song <[e-mail]>
Reviewed-by: Zi Yan <[e-mail]>
Cc: Kirill A. Shutemov <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Lars Persson <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Zi Yan <[e-mail]>
Cc: Xiongchun Duan <[e-mail]>
Cc: Fam Zheng <[e-mail]>
Cc: Muchun Song <[e-mail]>
Cc: Axel Rasmussen <[e-mail]>
Cc: Peter Xu <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/huge_memory.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Patch

--- a/mm/huge_memory.c~mm-thp-fix-wrong-cache-flush-in-remove_migration_pmd
+++ a/mm/huge_memory.c
@@ -3197,7 +3197,6 @@  void remove_migration_pmd(struct page_vm
 	if (pmd_swp_uffd_wp(*pvmw->pmd))
 		pmde = pmd_wrprotect(pmd_mkuffd_wp(pmde));
 
-	flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
 	if (PageAnon(new))
 		page_add_anon_rmap(new, vma, mmun_start, true);
 	else
@@ -3205,6 +3204,8 @@  void remove_migration_pmd(struct page_vm
 	set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
 	if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
 		mlock_vma_page(new);
+
+	/* No need to invalidate - it was non-present before */
 	update_mmu_cache_pmd(vma, address, pvmw->pmd);
 }
 #endif