WIP/DNM / Support overlayfs whiteout character files

Related-Issue: ostreedev#2712

src/libostree/ostree-core-private.h

@@ -34,6 +34,11 @@ G_BEGIN_DECLS
 #define DEFAULT_DIRECTORY_MODE 0775
 #define DEFAULT_REGFILE_MODE 0660
 
+/* Macros to identify the file mode of an overlayfs whiteout, or a file stat for a whiteout
+ ∫*/
+#define S_ISWHITEOUT(mode) (S_ISCHR (mode) && ((mode & ~S_IFMT) == 0))
+#define ST_ISWHITEOUT(st) (S_ISWHITEOUT (st.st_mode) && st.st_rdev == 0)
+
 /* This file contains private implementation data format definitions
  * read by multiple implementation .c files.
  */

src/libostree/ostree-core.c

@@ -827,7 +827,7 @@ gboolean ostree_break_hardlink (int               dfd,
     return glnx_file_copy_at (dfd, path, &stbuf, dfd, path,
                               copyflags | GLNX_FILE_COPY_OVERWRITE,
                               cancellable, error);
-  else if (S_ISLNK (stbuf.st_mode))
+  else if (S_ISLNK (stbuf.st_mode) || ST_ISWHITEOUT (stbuf)) //WIP:verify break_symhardlink and glnx can handle a char dev
     return break_symhardlink (dfd, path, &stbuf, copyflags,
                               cancellable, error);
   else
@@ -929,6 +929,8 @@ ostree_checksum_file_from_input (GFileInfo        *file_info,
             return FALSE;
         }
     }
+  // WIP: handle whiteouts in checksum, those have no content?, but we should probably
+  // avoid trying to read from them
 
   *out_csum = g_malloc (OSTREE_SHA256_DIGEST_LEN);
   ot_checksum_get_digest (&checksum, *out_csum, OSTREE_SHA256_DIGEST_LEN);
@@ -1051,6 +1053,8 @@ ostree_checksum_file_at (int               dfd,
         return FALSE;
     }
 
+    // WIP: whiteouts?
+
   const gboolean ignore_xattrs =
     ((flags & OSTREE_CHECKSUM_FLAGS_IGNORE_XATTRS) > 0);
 
@@ -2014,7 +2018,7 @@ file_header_parse (GVariant         *metadata,
   mode = GUINT32_FROM_BE (mode);
   g_autoptr(GFileInfo) ret_file_info = _ostree_mode_uidgid_to_gfileinfo (mode, uid, gid);
 
-  if (S_ISREG (mode))
+  if (S_ISREG (mode) || S_ISWHITEOUT(mode))
     {
       ;
     }
@@ -2065,7 +2069,7 @@ zlib_file_header_parse (GVariant         *metadata,
   g_autoptr(GFileInfo) ret_file_info = _ostree_mode_uidgid_to_gfileinfo (mode, uid, gid);
   g_file_info_set_size (ret_file_info, GUINT64_FROM_BE (size));
 
-  if (S_ISREG (mode))
+  if (S_ISREG (mode) || S_ISWHITEOUT (mode))
     {
       ;
     }
@@ -2370,6 +2374,7 @@ _ostree_validate_bareuseronly_mode (guint32     content_mode,
     }
   else if (S_ISLNK (content_mode))
     ; /* Nothing */
+  // WIP: IS_WHITEOUT does need special handling here?
   else
     g_assert_not_reached ();
 
@@ -2400,7 +2405,7 @@ gboolean
 ostree_validate_structureof_file_mode (guint32            mode,
                                        GError           **error)
 {
-  if (!(S_ISREG (mode) || S_ISLNK (mode)))
+  if (!(S_ISREG (mode) || S_ISLNK (mode) || S_ISWHITEOUT(mode)))
     return glnx_throw (error, "Invalid file metadata mode %u; not a valid file type", mode);
 
   if (!validate_stat_mode_perms (mode, error))

src/libostree/ostree-repo-checkout.c

@@ -398,6 +398,14 @@ create_file_copy_from_input_at (OstreeRepo     *repo,
                                  error))
         return FALSE;
     }
+  else if (g_file_info_get_file_type (file_info) == G_FILE_TYPE_SPECIAL)
+    {
+       guint32 file_mode = g_file_info_get_attribute_uint32 (file_info, "unix::mode");
+       g_assert(S_ISWHITEOUT(file_mode));
+       if (mknodat(destination_dfd, destination_name, file_mode, (dev_t)0) < 0) {
+          return glnx_throw_errno_prefix (error, "Creating whiteout char device");
+       }
+    }
   else
     g_assert_not_reached ();
 

src/libostree/ostree-repo-commit.c

@@ -301,7 +301,7 @@ commit_loose_regfile_object (OstreeRepo        *self,
             return FALSE;
         }
       else
-        g_assert (S_ISLNK (mode));
+        g_assert (S_ISLNK (mode) || S_ISWHITEOUT(mode));
     }
   else if (self->mode == OSTREE_REPO_MODE_BARE_USER_ONLY)
     {
@@ -969,6 +969,7 @@ write_content_object (OstreeRepo         *self,
   gboolean phys_object_is_symlink = FALSE;
   switch (object_file_type)
     {
+    case G_FILE_TYPE_SPECIAL: // WIP do additional checks for S_ISWHITEOUT ? 
     case G_FILE_TYPE_REGULAR:
       break;
     case G_FILE_TYPE_SYMBOLIC_LINK:
@@ -3739,6 +3740,8 @@ write_content_to_mtree_internal (OstreeRepo                  *self,
     {
     case G_FILE_TYPE_SYMBOLIC_LINK:
     case G_FILE_TYPE_REGULAR:
+    case G_FILE_TYPE_SPECIAL: // WIP should we also check here for S_ISWHITEOUT on mode to
+                              // be more precise?
       break;
     default:
       return glnx_throw (error, "Unsupported file type for file: '%s'", child_relpath);
@@ -4090,7 +4093,7 @@ write_dfd_iter_to_mtree_internal (OstreeRepo                  *self,
           continue;
         }
 
-      if (S_ISREG (stbuf.st_mode))
+      if (S_ISREG (stbuf.st_mode) || S_ISWHITEOUT(stbuf.st_mode))
         ;
       else if (S_ISLNK (stbuf.st_mode))
         {

src/libostree/ostree-repo-static-delta-compilation.c

@@ -514,6 +514,11 @@ process_one_object (OstreeRepo                       *repo,
             g_memory_input_stream_new_from_data (target, strlen (target), NULL);
           content_size = strlen (target);
         }
+      else if (S_ISWHITEOUT(mode))
+        {
+          // WIP: can a whiteout trigger a delta?
+          g_assert(0);
+        }
       else
         {
           g_assert (S_ISREG (mode));

src/libostree/ostree-repo.c

@@ -4322,8 +4322,8 @@ _ostree_repo_load_file_bare (OstreeRepo         *self,
         return glnx_throw_errno_prefix (error, "openat");
     }
 
-  if (!(S_ISREG (stbuf.st_mode) || S_ISLNK (stbuf.st_mode)))
-    return glnx_throw (error, "Not a regular file or symlink");
+  if (!(S_ISREG (stbuf.st_mode) || S_ISLNK (stbuf.st_mode) || S_ISWHITEOUT (stbuf.st_mode)))
+    return glnx_throw (error, "Not a regular file, symlink or whiteout");
 
   /* In the non-bare-user case, gather symlink info if requested */
   if (self->mode != OSTREE_REPO_MODE_BARE_USER