Merge patch series "ovl: simplify ovl_parse_param_lowerdir()"

Simplify and fix overlayfs layer parsing so the maximum of 500 layers
can be used.

* patches from https://lore.kernel.org/r/20240705011510.794025-1-chengzhihao1@huawei.com:
  ovl: ovl_parse_param_lowerdir: Add missed '\n' for pr_err
  ovl: fix wrong lowerdir number check for parameter Opt_lowerdir
  ovl: pass string to ovl_parse_layer()

Link: https://lore.kernel.org/r/20240705011510.794025-1-chengzhihao1@huawei.comSigned-off-by: Christian Brauner <brauner@kernel.org>

fs/overlayfs/params.c

@@ -353,6 +353,8 @@ static void ovl_add_layer(struct fs_context *fc, enum ovl_opt layer,
 	case Opt_datadir_add:
 		ctx->nr_data++;
 		fallthrough;
+	case Opt_lowerdir:
+		fallthrough;
 	case Opt_lowerdir_add:
 		WARN_ON(ctx->nr >= ctx->capacity);
 		l = &ctx->lower[ctx->nr++];
@@ -365,10 +367,9 @@ static void ovl_add_layer(struct fs_context *fc, enum ovl_opt layer,
 	}
 }
 
-static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
-			   enum ovl_opt layer)
+static int ovl_parse_layer(struct fs_context *fc, const char *layer_name, enum ovl_opt layer)
 {
-	char *name = kstrdup(param->string, GFP_KERNEL);
+	char *name = kstrdup(layer_name, GFP_KERNEL);
 	bool upper = (layer == Opt_upperdir || layer == Opt_workdir);
 	struct path path;
 	int err;
@@ -376,7 +377,7 @@ static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
 	if (!name)
 		return -ENOMEM;
 
-	if (upper)
+	if (upper || layer == Opt_lowerdir)
 		err = ovl_mount_dir(name, &path);
 	else
 		err = ovl_mount_dir_noesc(name, &path);
@@ -432,7 +433,6 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 {
 	int err;
 	struct ovl_fs_context *ctx = fc->fs_private;
-	struct ovl_fs_context_layer *l;
 	char *dup = NULL, *iter;
 	ssize_t nr_lower, nr;
 	bool data_layer = false;
@@ -449,7 +449,7 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 		return 0;
 
 	if (*name == ':') {
-		pr_err("cannot append lower layer");
+		pr_err("cannot append lower layer\n");
 		return -EINVAL;
 	}
 
@@ -472,35 +472,11 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 		goto out_err;
 	}
 
-	if (nr_lower > ctx->capacity) {
-		err = -ENOMEM;
-		l = krealloc_array(ctx->lower, nr_lower, sizeof(*ctx->lower),
-				   GFP_KERNEL_ACCOUNT);
-		if (!l)
-			goto out_err;
-
-		ctx->lower = l;
-		ctx->capacity = nr_lower;
-	}
-
 	iter = dup;
-	l = ctx->lower;
-	for (nr = 0; nr < nr_lower; nr++, l++) {
-		ctx->nr++;
-		memset(l, 0, sizeof(*l));
-
-		err = ovl_mount_dir(iter, &l->path);
+	for (nr = 0; nr < nr_lower; nr++) {
+		err = ovl_parse_layer(fc, iter, Opt_lowerdir);
 		if (err)
-			goto out_put;
-
-		err = ovl_mount_dir_check(fc, &l->path, Opt_lowerdir, iter, false);
-		if (err)
-			goto out_put;
-
-		err = -ENOMEM;
-		l->name = kstrdup(iter, GFP_KERNEL_ACCOUNT);
-		if (!l->name)
-			goto out_put;
+			goto out_err;
 
 		if (data_layer)
 			ctx->nr_data++;
@@ -517,8 +493,8 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 			 * there are no data layers.
 			 */
 			if (ctx->nr_data > 0) {
-				pr_err("regular lower layers cannot follow data lower layers");
-				goto out_put;
+				pr_err("regular lower layers cannot follow data lower layers\n");
+				goto out_err;
 			}
 
 			data_layer = false;
@@ -532,9 +508,6 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 	kfree(dup);
 	return 0;
 
-out_put:
-	ovl_reset_lowerdirs(ctx);
-
 out_err:
 	kfree(dup);
 
@@ -582,7 +555,7 @@ static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	case Opt_datadir_add:
 	case Opt_upperdir:
 	case Opt_workdir:
-		err = ovl_parse_layer(fc, param, opt);
+		err = ovl_parse_layer(fc, param->string, opt);
 		break;
 	case Opt_default_permissions:
 		config->default_permissions = true;