lockdep, mm: fix might_fault() annotation

Some code (nfs/sunrpc) uses socket ops on kernel memory while holding the mmap_sem, this is safe because kernel memory doesn't get paged out, therefore we'll never actually fault, and the might_fault() annotations will generate false positives. Reported-by: "J. Bruce Fields" <bfields@fieldses.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>

lockdep, mm: fix might_fault() annotation
Some code (nfs/sunrpc) uses socket ops on kernel memory while holding the mmap_sem, this is safe because kernel memory doesn't get paged out, therefore we'll never actually fault, and the might_fault() annotations will generate false positives. Reported-by: "J. Bruce Fields" <bfields@fieldses.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Peter Zijlstra · Ingo Molnar
1 parent 9d07933709
Showing 1 changed file with 9 additions and 0 deletions Side-by-side Diff
mm/memory.c
@@ -3165,6 +3165,15 @@
 #ifdef CONFIG_PROVE_LOCKING
 void might_fault(void)
 {
+	/*
+	 * Some code (nfs/sunrpc) uses socket ops on kernel memory while
+	 * holding the mmap_sem, this is safe because kernel memory doesn't
+	 * get paged out, therefore we'll never actually fault, and the
+	 * below annotations will generate false positives.
+	 */
+	if (segment_eq(get_fs(), KERNEL_DS))
+		return;
+
 	might_sleep();
 	/*
 	 * it would be nicer only to annotate paths which are not under
...	...	@@ -3165,6 +3165,15 @@
3165	3165	#ifdef CONFIG_PROVE_LOCKING
3166	3166	void might_fault(void)
3167	3167	{
	3168	+ /*
	3169	+ * Some code (nfs/sunrpc) uses socket ops on kernel memory while
	3170	+ * holding the mmap_sem, this is safe because kernel memory doesn't
	3171	+ * get paged out, therefore we'll never actually fault, and the
	3172	+ * below annotations will generate false positives.
	3173	+ */
	3174	+ if (segment_eq(get_fs(), KERNEL_DS))
	3175	+ return;
	3176	+
3168	3177	might_sleep();
3169	3178	/*
3170	3179	* it would be nicer only to annotate paths which are not under