Re: [PATCH v3 1/2] mm: migration: fix migration of huge PMD shared pages
From: Kirill A. Shutemov <hidden>
Date: 2018-08-22 21:13:58
Also in:
linux-mm, lkml
On Tue, Aug 21, 2018 at 06:10:42PM -0700, Mike Kravetz wrote:
quoted hunk ↗ jump to hunk
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 3103099f64fd..f085019a4724 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c@@ -4555,6 +4555,9 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) /* * check on proper vm_flags and page table alignment + * + * Note that this is the same check used in huge_pmd_sharing_possible. + * If you change one, consider changing both.
Should we have helper to isolate the check in one place?
quoted hunk ↗ jump to hunk
*/ if (vma->vm_flags & VM_MAYSHARE && vma->vm_start <= base && end <= vma->vm_end)@@ -4562,6 +4565,43 @@ static bool vma_shareable(struct vm_area_struct *vma, unsigned long addr) return false; } +/* + * Determine if start,end range within vma could be mapped by shared pmd. + * If yes, adjust start and end to cover range associated with possible + * shared pmd mappings. + */ +bool huge_pmd_sharing_possible(struct vm_area_struct *vma, + unsigned long *start, unsigned long *end) +{ + unsigned long check_addr = *start; + bool ret = false; + + if (!(vma->vm_flags & VM_MAYSHARE)) + return ret;
Do we ever use return value? I don't see it. And in this case function name is not really work...
+ for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) {
+ unsigned long a_start = check_addr & PUD_MASK;
+ unsigned long a_end = a_start + PUD_SIZE;
+
+ /*
+ * If sharing is possible, adjust start/end if necessary.
+ *
+ * Note that this is the same check used in vma_shareable. If
+ * you change one, consider changing both.
+ */
+ if (vma->vm_start <= a_start && a_end <= vma->vm_end) {
+ if (a_start < *start)
+ *start = a_start;
+ if (a_end > *end)
+ *end = a_end;
+
+ ret = true;
+ }
+ }
+
+ return ret;
+}
+-- Kirill A. Shutemov