mm: numa: do not clear PTE for pte_numa update

The TLB must be flushed if the PTE is updated but change_pte_range is
clearing the PTE while marking PTEs pte_numa without necessarily
flushing the TLB if it reinserts the same entry.  Without the flush,
it's conceivable that two processors have different TLBs for the same
virtual address and at the very least it would generate spurious faults.

This patch only unmaps the pages in change_pte_range for a full
protection change.

[[email protected]: write pte_numa pte back to the page tables]
Signed-off-by: Mel Gorman <[email protected]>
Signed-off-by: Rik van Riel <[email protected]>
Reviewed-by: Rik van Riel <[email protected]>
Cc: Alex Thorlton <[email protected]>
Cc: Chegu Vinod <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 26667971c824b08ca3dae7188a965e1e4efe0b79..1291a053b167d7c8a2d7b321cd5b1ee84967f04b 100644 (file)
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -52,17 +52,19 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
                        pte_t ptent;
                        bool updated = false;
 
-                       ptent = ptep_modify_prot_start(mm, addr, pte);
                        if (!prot_numa) {
+                               ptent = ptep_modify_prot_start(mm, addr, pte);
                                ptent = pte_modify(ptent, newprot);
                                updated = true;
                        } else {
                                struct page *page;
 
+                               ptent = *pte;
                                page = vm_normal_page(vma, addr, oldpte);
                                if (page) {
                                        if (!pte_numa(oldpte)) {
                                                ptent = pte_mknuma(ptent);
+                                               set_pte_at(mm, addr, pte, ptent);
                                                updated = true;
                                        }
                                }
@@ -79,7 +81,10 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 
                        if (updated)
                                pages++;
-                       ptep_modify_prot_commit(mm, addr, pte, ptent);
+
+                       /* Only !prot_numa always clears the pte */
+                       if (!prot_numa)
+                               ptep_modify_prot_commit(mm, addr, pte, ptent);
                } else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) {
                        swp_entry_t entry = pte_to_swp_entry(oldpte);