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authorLinus Torvalds2021-01-09 17:09:10 -0800
committerLinus Torvalds2021-01-16 10:51:26 -0800
commit9348b73c2e1bfea74ccd4a44fb4ccc7276ab9623 (patch)
tree1dfb123d7279ddfcbaa4a3a11df52cf51b0a0402
parent29a951dfb3c3263c3a0f3bd9f7f2c2cfde4baedb (diff)
mm: don't play games with pinned pages in clear_page_refs
Turning a pinned page read-only breaks the pinning after COW. Don't do it. The whole "track page soft dirty" state doesn't work with pinned pages anyway, since the page might be dirtied by the pinning entity without ever being noticed in the page tables. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/proc/task_mmu.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index ab7d700b2caa..602e3a52884d 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1035,6 +1035,25 @@ struct clear_refs_private {
};
#ifdef CONFIG_MEM_SOFT_DIRTY
+
+#define is_cow_mapping(flags) (((flags) & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE)
+
+static inline bool pte_is_pinned(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
+{
+ struct page *page;
+
+ if (!pte_write(pte))
+ return false;
+ if (!is_cow_mapping(vma->vm_flags))
+ return false;
+ if (likely(!atomic_read(&vma->vm_mm->has_pinned)))
+ return false;
+ page = vm_normal_page(vma, addr, pte);
+ if (!page)
+ return false;
+ return page_maybe_dma_pinned(page);
+}
+
static inline void clear_soft_dirty(struct vm_area_struct *vma,
unsigned long addr, pte_t *pte)
{
@@ -1049,6 +1068,8 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
if (pte_present(ptent)) {
pte_t old_pte;
+ if (pte_is_pinned(vma, addr, ptent))
+ return;
old_pte = ptep_modify_prot_start(vma, addr, pte);
ptent = pte_wrprotect(old_pte);
ptent = pte_clear_soft_dirty(ptent);