only regular files with FMODE_WRITE need to be on s_files

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/file_table.c

@@ -385,6 +385,10 @@ static inline void __file_sb_list_add(struct file *file, struct super_block *sb)
  */
 void file_sb_list_add(struct file *file, struct super_block *sb)
 {
+	if (likely(!(file->f_mode & FMODE_WRITE)))
+		return;
+	if (!S_ISREG(file_inode(file)->i_mode))
+		return;
 	lg_local_lock(&files_lglock);
 	__file_sb_list_add(file, sb);
 	lg_local_unlock(&files_lglock);
@@ -450,8 +454,6 @@ void mark_files_ro(struct super_block *sb)
 
 	lg_global_lock(&files_lglock);
 	do_file_list_for_each_entry(sb, f) {
-		if (!S_ISREG(file_inode(f)->i_mode))
-		       continue;
 		if (!file_count(f))
 			continue;
 		if (!(f->f_mode & FMODE_WRITE))