mm/damon/dbgfs: use damon_select_ops() instead of damon_{v,p}a_set_operations()

This commit makes DAMON debugfs interface to select the registered
monitoring operations for the physical address space or virtual address
spaces depending on user requests instead of setting it on its own.  Note
that DAMON debugfs interface is still dependent to DAMON_VADDR with this
change, because it is also using its symbol, 'damon_va_target_valid'.

Link: https://lkml.kernel.org/r/20220215184603.1479-6-sj@kernel.orgSigned-off-by: NSeongJae Park <sj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Xin Hao <xhao@linux.alibaba.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/damon/dbgfs.c

@@ -474,12 +474,18 @@ static ssize_t dbgfs_target_ids_write(struct file *file,
 
 	/* remove previously set targets */
 	dbgfs_set_targets(ctx, 0, NULL);
+	if (!nr_targets) {
+		ret = count;
+		goto unlock_out;
+	}
 
 	/* Configure the context for the address space type */
 	if (id_is_pid)
-		damon_va_set_operations(ctx);
+		ret = damon_select_ops(ctx, DAMON_OPS_VADDR);
 	else
-		damon_pa_set_operations(ctx);
+		ret = damon_select_ops(ctx, DAMON_OPS_PADDR);
+	if (ret)
+		goto unlock_out;
 
 	ret = dbgfs_set_targets(ctx, nr_targets, target_pids);
 	if (!ret)
@@ -735,7 +741,11 @@ static struct damon_ctx *dbgfs_new_ctx(void)
 	if (!ctx)
 		return NULL;
 
-	damon_va_set_operations(ctx);
+	if (damon_select_ops(ctx, DAMON_OPS_VADDR) && damon_select_ops(ctx,
+				DAMON_OPS_PADDR)) {
+		damon_destroy_ctx(ctx);
+		return NULL;
+	}
 	ctx->callback.before_terminate = dbgfs_before_terminate;
 	return ctx;
 }