Don't unnecessarily rebuild exported metadata resources

[wimlib] / src / write.c

diff --git a/src/write.c b/src/write.c
index a649dfa4e36b0dc20c492bccb1d3bc264004e35d..0a899945620acd59f04ddc6239fb2d37abdebd91 100644 (file)
--- a/src/write.c
+++ b/src/write.c
@@ -2179,20 +2179,28 @@ write_metadata_resources(WIMStruct *wim, int image, int write_flags)
                struct wim_image_metadata *imd;
 
                imd = wim->image_metadata[i - 1];
-               /* Build a new metadata resource only if image was modified from
-                * the original (or was newly added).  Otherwise just copy the
-                * existing one.  */
-               if (imd->modified) {
+               if (is_image_dirty(imd)) {
+                       /* The image was modified from the original, or was
+                        * newly added, so we have to build and write a new
+                        * metadata resource.  */
                        ret = write_metadata_resource(wim, i,
                                                      write_resource_flags);
-               } else if (write_flags & WIMLIB_WRITE_FLAG_UNSAFE_COMPACT) {
-                       /* For compactions, existing metadata resources are
-                        * written along with the existing file resources.  */
-                       ret = 0;
-               } else if (write_flags & WIMLIB_WRITE_FLAG_APPEND) {
-                       blob_set_out_reshdr_for_reuse(imd->metadata_blob);
+               } else if (is_image_unchanged_from_wim(imd, wim) &&
+                          (write_flags & (WIMLIB_WRITE_FLAG_UNSAFE_COMPACT |
+                                          WIMLIB_WRITE_FLAG_APPEND)))
+               {
+                       /* The metadata resource is already in the WIM file.
+                        * For appends, we don't need to write it at all.  For
+                        * compactions, we re-write existing metadata resources
+                        * along with the existing file resources, not here.  */
+                       if (write_flags & WIMLIB_WRITE_FLAG_APPEND)
+                               blob_set_out_reshdr_for_reuse(imd->metadata_blob);
                        ret = 0;
                } else {
+                       /* The metadata resource is in a WIM file other than the
+                        * one being written to.  We need to rewrite it,
+                        * possibly compressed differently; but rebuilding the
+                        * metadata itself isn't necessary.  */
                        ret = write_wim_resource(imd->metadata_blob,
                                                 &wim->out_fd,
                                                 wim->out_compression_type,
@@ -2880,11 +2888,16 @@ wimlib_write_to_fd(WIMStruct *wim, int fd,
        return write_standalone_wim(wim, &fd, image, write_flags, num_threads);
 }
 
+/* Have there been any changes to images in the specified WIM, including updates
+ * as well as deletions and additions of entire images, but excluding changes to
+ * the XML document?  */
 static bool
-any_images_modified(WIMStruct *wim)
+any_images_changed(WIMStruct *wim)
 {
+       if (wim->image_deletion_occurred)
+               return true;
        for (int i = 0; i < wim->hdr.image_count; i++)
-               if (wim->image_metadata[i]->modified)
+               if (!is_image_unchanged_from_wim(wim->image_metadata[i], wim))
                        return true;
        return false;
 }
@@ -3045,7 +3058,7 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags, unsigned num_threads)
                         * with the file resources.  */
                        for (int i = 0; i < wim->hdr.image_count; i++) {
                                struct wim_image_metadata *imd = wim->image_metadata[i];
-                               if (!imd->modified) {
+                               if (is_image_unchanged_from_wim(imd, wim)) {
                                        fully_reference_blob_for_write(imd->metadata_blob,
                                                                       &blob_list);
                                }
@@ -3083,13 +3096,13 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags, unsigned num_threads)
                 * don't allow any file and metadata resources to appear without
                 * returning WIMLIB_ERR_RESOURCE_ORDER (due to the fact that we
                 * would otherwise overwrite these resources). */
-               if (!wim->image_deletion_occurred && !any_images_modified(wim)) {
-                       /* If no images have been modified and no images have
-                        * been deleted, a new blob table does not need to be
-                        * written.  We shall write the new XML data and
-                        * optional integrity table immediately after the blob
-                        * table.  Note that this may overwrite an existing
-                        * integrity table. */
+               if (!any_images_changed(wim)) {
+                       /* If no images have been modified, added, or deleted,
+                        * then a new blob table does not need to be written.
+                        * We shall write the new XML data and optional
+                        * integrity table immediately after the blob table.
+                        * Note that this may overwrite an existing integrity
+                        * table.  */
                        old_wim_end = old_blob_table_end;
                        write_flags |= WIMLIB_WRITE_FLAG_NO_NEW_BLOBS;
                } else if (wim_has_integrity_table(wim)) {