Merge branch 'safe-dirty-tlb-flush'

This merges the patch to fix possible loss of dirty bit on munmap() or
madvice(DONTNEED). If there are concurrent writers on other CPU's that
have the unmapped/unneeded page in their TLBs, their writes to the page
could possibly get lost if a third CPU raced with the TLB flush and did
a page_mkclean() before the page was fully written.

Admittedly, if you unmap() or madvice(DONTNEED) an area _while_ another
thread is still busy writing to it, you deserve all the lost writes you
could get. But we kernel people hold ourselves to higher quality
standards than "crazy people deserve to lose", because, well, we've seen
people do all kinds of crazy things.

So let's get it right, just because we can, and we don't have to worry
about it.

* safe-dirty-tlb-flush:
mm: split 'tlb_flush_mmu()' into tlb flushing and memory freeing parts

arch/arm/include/asm/tlb.h

···
 	}
 }
 
-static inline void tlb_flush_mmu(struct mmu_gather *tlb)
+static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
 {
 	tlb_flush(tlb);
+}
+
+static inline void tlb_flush_mmu_free(struct mmu_gather *tlb)
+{
 	free_pages_and_swap_cache(tlb->pages, tlb->nr);
 	tlb->nr = 0;
 	if (tlb->pages == tlb->local)
 		__tlb_alloc_page(tlb);
+}
+
+static inline void tlb_flush_mmu(struct mmu_gather *tlb)
+{
+	tlb_flush_mmu_tlbonly(tlb);
+	tlb_flush_mmu_free(tlb);
 }
 
 static inline void

arch/ia64/include/asm/tlb.h

···
 #define RR_RID_MASK	0x00000000ffffff00L
 #define RR_TO_RID(val) 	((val >> 8) & 0xffffff)
 
-/*
- * Flush the TLB for address range START to END and, if not in fast mode, release the
- * freed pages that where gathered up to this point.
- */
 static inline void
-ia64_tlb_flush_mmu (struct mmu_gather *tlb, unsigned long start, unsigned long end)
+ia64_tlb_flush_mmu_tlbonly(struct mmu_gather *tlb, unsigned long start, unsigned long end)
 {
-	unsigned long i;
-	unsigned int nr;
-
-	if (!tlb->need_flush)
-		return;
 	tlb->need_flush = 0;
 
 	if (tlb->fullmm) {
···
 		flush_tlb_range(&vma, ia64_thash(start), ia64_thash(end));
 	}
 
+}
+
+static inline void
+ia64_tlb_flush_mmu_free(struct mmu_gather *tlb)
+{
+	unsigned long i;
+	unsigned int nr;
+
 	/* lastly, release the freed pages */
 	nr = tlb->nr;
 
···
 	tlb->start_addr = ~0UL;
 	for (i = 0; i < nr; ++i)
 		free_page_and_swap_cache(tlb->pages[i]);
+}
+
+/*
+ * Flush the TLB for address range START to END and, if not in fast mode, release the
+ * freed pages that where gathered up to this point.
+ */
+static inline void
+ia64_tlb_flush_mmu (struct mmu_gather *tlb, unsigned long start, unsigned long end)
+{
+	if (!tlb->need_flush)
+		return;
+	ia64_tlb_flush_mmu_tlbonly(tlb, start, end);
+	ia64_tlb_flush_mmu_free(tlb);
 }
 
 static inline void __tlb_alloc_page(struct mmu_gather *tlb)
···
 	VM_BUG_ON(tlb->nr > tlb->max);
 
 	return tlb->max - tlb->nr;
+}
+
+static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
+{
+	ia64_tlb_flush_mmu_tlbonly(tlb, tlb->start_addr, tlb->end_addr);
+}
+
+static inline void tlb_flush_mmu_free(struct mmu_gather *tlb)
+{
+	ia64_tlb_flush_mmu_free(tlb);
 }
 
 static inline void tlb_flush_mmu(struct mmu_gather *tlb)

arch/s390/include/asm/tlb.h

···
 	tlb->batch = NULL;
 }
 
-static inline void tlb_flush_mmu(struct mmu_gather *tlb)
+static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
 {
 	__tlb_flush_mm_lazy(tlb->mm);
+}
+
+static inline void tlb_flush_mmu_free(struct mmu_gather *tlb)
+{
 	tlb_table_flush(tlb);
+}
+
+
+static inline void tlb_flush_mmu(struct mmu_gather *tlb)
+{
+	tlb_flush_mmu_tlbonly(tlb);
+	tlb_flush_mmu_free(tlb);
 }
 
 static inline void tlb_finish_mmu(struct mmu_gather *tlb,

arch/sh/include/asm/tlb.h

···
 	}
 }
 
+static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
+{
+}
+
+static inline void tlb_flush_mmu_free(struct mmu_gather *tlb)
+{
+}
+
 static inline void tlb_flush_mmu(struct mmu_gather *tlb)
 {
 }

arch/um/include/asm/tlb.h

···
 			       unsigned long end);
 
 static inline void
+tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
+{
+	flush_tlb_mm_range(tlb->mm, tlb->start, tlb->end);
+}
+
+static inline void
+tlb_flush_mmu_free(struct mmu_gather *tlb)
+{
+	init_tlb_gather(tlb);
+}
+
+static inline void
 tlb_flush_mmu(struct mmu_gather *tlb)
 {
 	if (!tlb->need_flush)
 		return;
 
-	flush_tlb_mm_range(tlb->mm, tlb->start, tlb->end);
-	init_tlb_gather(tlb);
+	tlb_flush_mmu_tlbonly(tlb);
+	tlb_flush_mmu_free(tlb);
 }
 
 /* tlb_finish_mmu

mm/memory.c

···
 #endif
 }
 
-void tlb_flush_mmu(struct mmu_gather *tlb)
+static void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
 {
-	struct mmu_gather_batch *batch;
-
-	if (!tlb->need_flush)
-		return;
 	tlb->need_flush = 0;
 	tlb_flush(tlb);
 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
 	tlb_table_flush(tlb);
 #endif
+}
+
+static void tlb_flush_mmu_free(struct mmu_gather *tlb)
+{
+	struct mmu_gather_batch *batch;
 
 	for (batch = &tlb->local; batch; batch = batch->next) {
 		free_pages_and_swap_cache(batch->pages, batch->nr);
 		batch->nr = 0;
 	}
 	tlb->active = &tlb->local;
+}
+
+void tlb_flush_mmu(struct mmu_gather *tlb)
+{
+	if (!tlb->need_flush)
+		return;
+	tlb_flush_mmu_tlbonly(tlb);
+	tlb_flush_mmu_free(tlb);
 }
 
 /* tlb_finish_mmu
···
 			if (PageAnon(page))
 				rss[MM_ANONPAGES]--;
 			else {
-				if (pte_dirty(ptent))
+				if (pte_dirty(ptent)) {
+					force_flush = 1;
 					set_page_dirty(page);
+				}
 				if (pte_young(ptent) &&
 				    likely(!(vma->vm_flags & VM_SEQ_READ)))
 					mark_page_accessed(page);
···
 			page_remove_rmap(page);
 			if (unlikely(page_mapcount(page) < 0))
 				print_bad_pte(vma, addr, ptent, page);
-			force_flush = !__tlb_remove_page(tlb, page);
-			if (force_flush)
+			if (unlikely(!__tlb_remove_page(tlb, page))) {
+				force_flush = 1;
 				break;
+			}
 			continue;
 		}
 		/*
···
 
 	add_mm_rss_vec(mm, rss);
 	arch_leave_lazy_mmu_mode();
-	pte_unmap_unlock(start_pte, ptl);
 
-	/*
-	 * mmu_gather ran out of room to batch pages, we break out of
-	 * the PTE lock to avoid doing the potential expensive TLB invalidate
-	 * and page-free while holding it.
-	 */
+	/* Do the actual TLB flush before dropping ptl */
 	if (force_flush) {
 		unsigned long old_end;
-
-		force_flush = 0;
 
 		/*
 		 * Flush the TLB just for the previous segment,
···
 		 */
 		old_end = tlb->end;
 		tlb->end = addr;
-
-		tlb_flush_mmu(tlb);
-
+		tlb_flush_mmu_tlbonly(tlb);
 		tlb->start = addr;
 		tlb->end = old_end;
+	}
+	pte_unmap_unlock(start_pte, ptl);
+
+	/*
+	 * If we forced a TLB flush (either due to running out of
+	 * batch buffers or because we needed to flush dirty TLB
+	 * entries before releasing the ptl), free the batched
+	 * memory too. Restart if we didn't do everything.
+	 */
+	if (force_flush) {
+		force_flush = 0;
+		tlb_flush_mmu_free(tlb);
 
 		if (addr != end)
 			goto again;