jffs2: Allow setting rp_size to zero during remounting

Set rp_size to zero will be ignore during remounting.

The method to identify whether we input a remounting option of
rp_size is to check if the rp_size input is zero. It can not work
well if we pass "rp_size=0".

This patch add a bool variable "set_rp_size" to fix this problem.
Reported-by: Jubin Zhong <zhongjubin@huawei.com>
Signed-off-by: lizhe <lizhe67@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

fs/jffs2/jffs2_fs_sb.h

@@ -38,6 +38,7 @@ struct jffs2_mount_opts {
 	 * users. This is implemented simply by means of not allowing the
 	 * latter users to write to the file system if the amount if the
 	 * available space is less then 'rp_size'. */
+	bool set_rp_size;
 	unsigned int rp_size;
 };
 

fs/jffs2/super.c

@@ -88,7 +88,7 @@ static int jffs2_show_options(struct seq_file *s, struct dentry *root)
 
 	if (opts->override_compr)
 		seq_printf(s, ",compr=%s", jffs2_compr_name(opts->compr));
-	if (opts->rp_size)
+	if (opts->set_rp_size)
 		seq_printf(s, ",rp_size=%u", opts->rp_size / 1024);
 
 	return 0;
@@ -206,6 +206,7 @@ static int jffs2_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		if (opt > c->mtd->size)
 			return invalf(fc, "jffs2: Too large reserve pool specified, max is %llu KB",
 				      c->mtd->size / 1024);
+		c->mount_opts.set_rp_size = true;
 		c->mount_opts.rp_size = opt;
 		break;
 	default:
@@ -225,8 +226,10 @@ static inline void jffs2_update_mount_opts(struct fs_context *fc)
 		c->mount_opts.override_compr = new_c->mount_opts.override_compr;
 		c->mount_opts.compr = new_c->mount_opts.compr;
 	}
-	if (new_c->mount_opts.rp_size)
+	if (new_c->mount_opts.set_rp_size) {
+		c->mount_opts.set_rp_size = new_c->mount_opts.set_rp_size;
 		c->mount_opts.rp_size = new_c->mount_opts.rp_size;
+	}
 	mutex_unlock(&c->alloc_sem);
 }