On Tue, 14 Jul 2020 at 13:03, Kirill A. Shutemov kirill@shutemov.name wrote:
On Sun, Jul 12, 2020 at 03:58:06PM -0700, Linus Torvalds wrote:
Anybody else have any opinions?
Maybe we just shouldn't allow move_normal_pmd() if ranges overlap?
Other option: pass 'overlaps' down to move_normal_pmd() and only WARN() if see establised PMD without overlaps being true.
Untested patch:
This patch applied on top of Linus mainline tree and tested on i386. The reported warning did not happen while testing LTP mm [1].
diff --git a/mm/mremap.c b/mm/mremap.c index 5dd572d57ca9..e33fcee541fe 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -245,6 +245,18 @@ unsigned long move_page_tables(struct vm_area_struct *vma, unsigned long extent, next, old_end; struct mmu_notifier_range range; pmd_t *old_pmd, *new_pmd;
bool overlaps;/** shift_arg_pages() can call move_page_tables() on overlapping ranges.* In this case we cannot use move_normal_pmd() because destination pmd* might be established page table: move_ptes() doesn't free page* table.*/if (old_addr > new_addr)overlaps = old_addr - new_addr < len;elseoverlaps = new_addr - old_addr < len; old_end = old_addr + len; flush_cache_range(vma, old_addr, old_end);@@ -282,7 +294,7 @@ unsigned long move_page_tables(struct vm_area_struct *vma, split_huge_pmd(vma, old_pmd, old_addr); if (pmd_trans_unstable(old_pmd)) continue;
} else if (extent == PMD_SIZE) {
} else if (!overlaps && extent == PMD_SIZE) {#ifdef CONFIG_HAVE_MOVE_PMD /* * If the extent is PMD-sized, try to speed the move by -- Kirill A. Shutemov
ref: https://lkft.validation.linaro.org/scheduler/job/1561734#L1598
- Naresh