plugins: allow to manage multiple layers with a ds

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

direct.c

@@ -160,7 +160,7 @@ direct_readlinkat (struct ovl_layer *l, const char *path, char *buf, size_t bufs
 }
 
 static int
-direct_load_data_source (struct ovl_layer *l, const char *opaque, const char *path)
+direct_load_data_source (struct ovl_layer *l, const char *opaque, const char *path, int n_layer)
 {
   l->path = realpath (path, NULL);
   if (l->path == NULL)
@@ -186,8 +186,15 @@ direct_cleanup (struct ovl_layer *l)
   return 0;
 }
 
+static int
+direct_num_of_layers (const char *opaque, const char *path)
+{
+  return 1;
+}
+
 struct data_source direct_access_ds =
   {
+   .num_of_layers = direct_num_of_layers,
    .load_data_source = direct_load_data_source,
    .cleanup = direct_cleanup,
    .file_exists = direct_file_exists,

fuse-overlayfs.h

@@ -119,7 +119,8 @@ struct ovl_layer
 /* a data_source defines the methods for accessing a lower layer.  */
 struct data_source
 {
-  int (*load_data_source)(struct ovl_layer *l, const char *opaque, const char *path);
+  int (*num_of_layers) (const char *opaque, const char *path);
+  int (*load_data_source)(struct ovl_layer *l, const char *opaque, const char *path, int n_layer);
   int (*cleanup)(struct ovl_layer *l);
   int (*file_exists)(struct ovl_layer *l, const char *pathname);
   int (*statat)(struct ovl_layer *l, const char *path, struct stat *st, int flags, unsigned int mask);

main.c

@@ -1549,16 +1549,14 @@ read_dirs (struct ovl_data *lo, char *path, bool low, struct ovl_layer *layers)
     {
       char *name, *data;
       char *it_path = it;
+      int i, n_layers;
       cleanup_layer struct ovl_layer *l = NULL;
-
+      struct data_source *ds;
-      l = calloc (1, sizeof (*l));
-      if (l == NULL)
-        return NULL;
 
       if (it[0] != '/' || it[1] != '/')
         {
           /* By default use the direct access data store.  */
-          l->ds = &direct_access_ds;
+          ds = &direct_access_ds;
 
           data = NULL;
           path = it_path;
@@ -1603,43 +1601,59 @@ read_dirs (struct ovl_data *lo, char *path, bool low, struct ovl_layer *layers)
               return NULL;
             }
 
-          l->ds = p->load (l, data, path);
+          ds = p->load (data, path);
-          if (l->ds == NULL)
+          if (ds == NULL)
             {
               fprintf (stderr, "cannot load plugin %s\n", name);
               return NULL;
             }
         }
 
-      l->ovl_data = lo;
+      n_layers = ds->num_of_layers (data, path);
-
+      if (n_layers < 0)
-      l->path = NULL;
-      l->fd = -1;
-
-      if (l->ds->load_data_source (l, data, path) < 0)
         {
-          fprintf (stderr, "cannot load store %s at %s\n", data, path);
+          fprintf (stderr, "cannot retrieve number of layers for %s\n", path);
           return NULL;
         }
 
-      l->low = low;
+      for (i = 0; i < n_layers; i++)
-      if (low)
         {
-          l->next = NULL;
+          l = calloc (1, sizeof (*l));
-          if (last == NULL)
+          if (l == NULL)
-            last = layers = l;
+            return NULL;
+
+          l->ds = ds;
+
+          l->ovl_data = lo;
+
+          l->path = NULL;
+          l->fd = -1;
+
+          if (l->ds->load_data_source (l, data, path, i) < 0)
+            {
+              fprintf (stderr, "cannot load store %s at %s\n", data, path);
+              return NULL;
+            }
+
+          l->low = low;
+          if (low)
+            {
+              l->next = NULL;
+              if (last == NULL)
+                last = layers = l;
+              else
+                {
+                  last->next = l;
+                  last = l;
+                }
+            }
           else
             {
-              last->next = l;
+              l->next = layers;
-              last = l;
+              layers = l;
             }
+          l = NULL;
         }
-      else
-        {
-          l->next = layers;
-          layers = l;
-        }
-      l = NULL;
     }
   return layers;
 }

plugin-manager.c

@@ -110,7 +110,10 @@ plugin_free_all (struct ovl_plugin_context *context)
     {
       next = it->next;
 
-      dlclose (it->handle);
+      it->release ();
+
+      /* Skip dlclose (it->handle) as it causes plugins written in Go to crash.  */
+
       free (it);
 
       it = next;

plugin.h

@@ -23,8 +23,8 @@
 # include <utils.h>
 # include <fuse-overlayfs.h>
 
-typedef struct data_source *(*plugin_load_data_source)(struct ovl_layer *layer, const char *opaque, const char *path);
+typedef struct data_source *(*plugin_load_data_source)(const char *opaque, const char *path);
-typedef int (*plugin_release)(struct ovl_layer *layer);
+typedef int (*plugin_release)();
 typedef const char *(*plugin_name)();
 typedef int (*plugin_version)();