main: refactor to use a data store

this is the first step towards supporting data from lower layers
coming from other sources.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

fuse-overlayfs.h

@@ -0,0 +1,127 @@
+/* fuse-overlayfs: Overlay Filesystem in Userspace
+
+   Copyright (C) 2019 Red Hat Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#ifndef FUSE_OVERLAYFS_H
+# define FUSE_OVERLAYFS_H
+
+# include <hash.h>
+# include <sys/stat.h>
+
+struct ovl_ino
+{
+  struct ovl_node *node;
+  ino_t ino;
+  dev_t dev;
+  int lookups;
+  mode_t mode;
+  int nlinks;
+};
+
+struct ovl_node
+{
+  struct ovl_node *parent;
+  Hash_table *children;
+  struct ovl_layer *layer, *last_layer;
+  ino_t tmp_ino;
+  dev_t tmp_dev;
+  char *path;
+  char *name;
+  int hidden_dirfd;
+  int node_lookups;
+  size_t name_hash;
+  Hash_table *inodes;
+  struct ovl_ino *ino;
+  struct ovl_node *next_link;
+
+  unsigned int do_unlink : 1;
+  unsigned int do_rmdir : 1;
+  unsigned int hidden : 1;
+  unsigned int whiteout : 1;
+  unsigned int loaded : 1;
+  unsigned int no_security_capability : 1;
+};
+
+struct ovl_mapping
+{
+  struct ovl_mapping *next;
+  unsigned int host;
+  unsigned int to;
+  unsigned int len;
+};
+
+struct ovl_data
+{
+  struct fuse_session *se;
+  char *uid_str;
+  char *gid_str;
+  struct ovl_mapping *uid_mappings;
+  struct ovl_mapping *gid_mappings;
+  char *mountpoint;
+  char *lowerdir;
+  char *context;
+  char *upperdir;
+  char *workdir;
+  char *redirect_dir;
+  int workdir_fd;
+  int debug;
+  struct ovl_layer *layers;
+
+  Hash_table *inodes;
+
+  struct ovl_node *root;
+  char *timeout_str;
+  double timeout;
+  int threaded;
+  int fsync;
+  int fast_ino_check;
+  int writeback;
+  int disable_xattrs;
+
+  /* current uid/gid*/
+  uid_t uid;
+  uid_t gid;
+};
+
+struct ovl_layer
+{
+  struct ovl_layer *next;
+  struct data_source *ds;
+  struct ovl_data *ovl_data;
+  char *path;
+  int fd;
+  bool low;
+};
+
+/* a data_source defines the methods for accessing a lower layer.  */
+struct data_source
+{
+  int (*file_exists)(struct ovl_layer *l, const char *pathname);
+  int (*statat)(struct ovl_layer *l, const char *path, struct stat *st, int flags);
+  int (*fstat)(struct ovl_layer *l, int fd, const char *path, struct stat *st);
+  void *(*opendir)(struct ovl_layer *l, const char *path);
+  struct dirent *(*readdir)(void *dirp);
+  int (*closedir)(void *dirp);
+  int (*openat)(struct ovl_layer *l, const char *path, int flags, mode_t mode);
+  int (*listxattr)(struct ovl_layer *l, const char *path, char *buf, size_t size);
+  int (*getxattr)(struct ovl_layer *l, const char *path, const char *name, char *buf, size_t size);
+  ssize_t (*readlinkat)(struct ovl_layer *l, const char *path, char *buf, size_t bufsiz);
+};
+
+/* passtrough to the file system.  */
+struct data_source direct_access_ds;
+
+#endif