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-rw-r--r--mm/rmap.c88
1 files changed, 66 insertions, 22 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index ced14f1af6dc..c1286d47aa1f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -605,6 +605,13 @@ static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
tlb_ubc->flush_required = true;
/*
+ * Ensure compiler does not re-order the setting of tlb_flush_batched
+ * before the PTE is cleared.
+ */
+ barrier();
+ mm->tlb_flush_batched = true;
+
+ /*
* If the PTE was dirty then it's best to assume it's writable. The
* caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
* before the page is queued for IO.
@@ -631,6 +638,35 @@ static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
return should_defer;
}
+
+/*
+ * Reclaim unmaps pages under the PTL but do not flush the TLB prior to
+ * releasing the PTL if TLB flushes are batched. It's possible for a parallel
+ * operation such as mprotect or munmap to race between reclaim unmapping
+ * the page and flushing the page. If this race occurs, it potentially allows
+ * access to data via a stale TLB entry. Tracking all mm's that have TLB
+ * batching in flight would be expensive during reclaim so instead track
+ * whether TLB batching occurred in the past and if so then do a flush here
+ * if required. This will cost one additional flush per reclaim cycle paid
+ * by the first operation at risk such as mprotect and mumap.
+ *
+ * This must be called under the PTL so that an access to tlb_flush_batched
+ * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
+ * via the PTL.
+ */
+void flush_tlb_batched_pending(struct mm_struct *mm)
+{
+ if (mm->tlb_flush_batched) {
+ flush_tlb_mm(mm);
+
+ /*
+ * Do not allow the compiler to re-order the clearing of
+ * tlb_flush_batched before the tlb is flushed.
+ */
+ barrier();
+ mm->tlb_flush_batched = false;
+ }
+}
#else
static void set_tlb_ubc_flush_pending(struct mm_struct *mm, bool writable)
{
@@ -852,10 +888,10 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma,
.flags = PVMW_SYNC,
};
int *cleaned = arg;
+ bool invalidation_needed = false;
while (page_vma_mapped_walk(&pvmw)) {
int ret = 0;
- address = pvmw.address;
if (pvmw.pte) {
pte_t entry;
pte_t *pte = pvmw.pte;
@@ -863,11 +899,11 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma,
if (!pte_dirty(*pte) && !pte_write(*pte))
continue;
- flush_cache_page(vma, address, pte_pfn(*pte));
- entry = ptep_clear_flush(vma, address, pte);
+ flush_cache_page(vma, pvmw.address, pte_pfn(*pte));
+ entry = ptep_clear_flush(vma, pvmw.address, pte);
entry = pte_wrprotect(entry);
entry = pte_mkclean(entry);
- set_pte_at(vma->vm_mm, address, pte, entry);
+ set_pte_at(vma->vm_mm, pvmw.address, pte, entry);
ret = 1;
} else {
#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
@@ -877,11 +913,11 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma,
if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
continue;
- flush_cache_page(vma, address, page_to_pfn(page));
- entry = pmdp_huge_clear_flush(vma, address, pmd);
+ flush_cache_page(vma, pvmw.address, page_to_pfn(page));
+ entry = pmdp_huge_clear_flush(vma, pvmw.address, pmd);
entry = pmd_wrprotect(entry);
entry = pmd_mkclean(entry);
- set_pmd_at(vma->vm_mm, address, pmd, entry);
+ set_pmd_at(vma->vm_mm, pvmw.address, pmd, entry);
ret = 1;
#else
/* unexpected pmd-mapped page? */
@@ -890,11 +926,16 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma,
}
if (ret) {
- mmu_notifier_invalidate_page(vma->vm_mm, address);
(*cleaned)++;
+ invalidation_needed = true;
}
}
+ if (invalidation_needed) {
+ mmu_notifier_invalidate_range(vma->vm_mm, address,
+ address + (1UL << compound_order(page)));
+ }
+
return true;
}
@@ -1287,7 +1328,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
};
pte_t pteval;
struct page *subpage;
- bool ret = true;
+ bool ret = true, invalidation_needed = false;
enum ttu_flags flags = (enum ttu_flags)arg;
/* munlock has nothing to gain from examining un-locked vmas */
@@ -1327,11 +1368,9 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
VM_BUG_ON_PAGE(!pvmw.pte, page);
subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte);
- address = pvmw.address;
-
if (!(flags & TTU_IGNORE_ACCESS)) {
- if (ptep_clear_flush_young_notify(vma, address,
+ if (ptep_clear_flush_young_notify(vma, pvmw.address,
pvmw.pte)) {
ret = false;
page_vma_mapped_walk_done(&pvmw);
@@ -1340,7 +1379,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
}
/* Nuke the page table entry. */
- flush_cache_page(vma, address, pte_pfn(*pvmw.pte));
+ flush_cache_page(vma, pvmw.address, pte_pfn(*pvmw.pte));
if (should_defer_flush(mm, flags)) {
/*
* We clear the PTE but do not flush so potentially
@@ -1350,11 +1389,12 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
* transition on a cached TLB entry is written through
* and traps if the PTE is unmapped.
*/
- pteval = ptep_get_and_clear(mm, address, pvmw.pte);
+ pteval = ptep_get_and_clear(mm, pvmw.address,
+ pvmw.pte);
set_tlb_ubc_flush_pending(mm, pte_dirty(pteval));
} else {
- pteval = ptep_clear_flush(vma, address, pvmw.pte);
+ pteval = ptep_clear_flush(vma, pvmw.address, pvmw.pte);
}
/* Move the dirty bit to the page. Now the pte is gone. */
@@ -1369,12 +1409,12 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
if (PageHuge(page)) {
int nr = 1 << compound_order(page);
hugetlb_count_sub(nr, mm);
- set_huge_swap_pte_at(mm, address,
+ set_huge_swap_pte_at(mm, pvmw.address,
pvmw.pte, pteval,
vma_mmu_pagesize(vma));
} else {
dec_mm_counter(mm, mm_counter(page));
- set_pte_at(mm, address, pvmw.pte, pteval);
+ set_pte_at(mm, pvmw.address, pvmw.pte, pteval);
}
} else if (pte_unused(pteval)) {
@@ -1398,7 +1438,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
swp_pte = swp_entry_to_pte(entry);
if (pte_soft_dirty(pteval))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
- set_pte_at(mm, address, pvmw.pte, swp_pte);
+ set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
} else if (PageAnon(page)) {
swp_entry_t entry = { .val = page_private(subpage) };
pte_t swp_pte;
@@ -1424,7 +1464,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
* If the page was redirtied, it cannot be
* discarded. Remap the page to page table.
*/
- set_pte_at(mm, address, pvmw.pte, pteval);
+ set_pte_at(mm, pvmw.address, pvmw.pte, pteval);
SetPageSwapBacked(page);
ret = false;
page_vma_mapped_walk_done(&pvmw);
@@ -1432,7 +1472,7 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
}
if (swap_duplicate(entry) < 0) {
- set_pte_at(mm, address, pvmw.pte, pteval);
+ set_pte_at(mm, pvmw.address, pvmw.pte, pteval);
ret = false;
page_vma_mapped_walk_done(&pvmw);
break;
@@ -1448,14 +1488,18 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
swp_pte = swp_entry_to_pte(entry);
if (pte_soft_dirty(pteval))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
- set_pte_at(mm, address, pvmw.pte, swp_pte);
+ set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
} else
dec_mm_counter(mm, mm_counter_file(page));
discard:
page_remove_rmap(subpage, PageHuge(page));
put_page(page);
- mmu_notifier_invalidate_page(mm, address);
+ invalidation_needed = true;
}
+
+ if (invalidation_needed)
+ mmu_notifier_invalidate_range(mm, address,
+ address + (1UL << compound_order(page)));
return ret;
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-24 21:44:57 +0000