Don't set FILE_ATTRIBUTE_SPARSE on Windows

[wimlib] / src / win32_apply.c

diff --git a/src/win32_apply.c b/src/win32_apply.c
index d744268613f9db1ed08c357bc3dd3f84676d13e1..3f4a4562567ba223183636f2836fde07fb0bf660 100644 (file)
--- a/src/win32_apply.c
+++ b/src/win32_apply.c
@@ -292,8 +292,10 @@ win32_start_extract(const wchar_t *path, struct apply_ctx *ctx)
 
        ctx->supported_features.not_context_indexed_files = 1;
 
+#if 0
        if (vol_flags & FILE_SUPPORTS_SPARSE_FILES)
                ctx->supported_features.sparse_files = 1;
+#endif
 
        if (vol_flags & FILE_NAMED_STREAMS)
                ctx->supported_features.named_data_streams = 1;
@@ -670,12 +672,27 @@ win32_set_special_file_attributes(const wchar_t *path, u32 attributes)
        if (h == INVALID_HANDLE_VALUE)
                goto error;
 
+       /* Don't make extracted files sparse.  It is pointless without also
+        * skipping over runs of zeroes when writing the file, and in fact
+        * increases disk usage --- apparently, allocation sizes in sparse files
+        * are rounded up to multiples of 131072 bytes rather than 4096 bytes.
+        * And in some Windows 7 images, *all* files are set as sparse for some
+        * reason, which causes 1 GB+ of disk space to be wasted on the target
+        * drive of a full extraction.
+        *
+        * WIMGAPI seemingly does not make extracted files sparse either.
+        *
+        * XXX: We really ought to do a proper sparse extraction anyway if the
+        * file meets some heuristic that indicates this would be beneficial.
+        */
+#if 0
        if (attributes & FILE_ATTRIBUTE_SPARSE_FILE)
                if (!DeviceIoControl(h, FSCTL_SET_SPARSE,
                                     NULL, 0,
                                     NULL, 0,
                                     &bytes_returned, NULL))
                        goto error_close_handle;
+#endif
 
        if (attributes & FILE_ATTRIBUTE_COMPRESSED)
                if (!DeviceIoControl(h, FSCTL_SET_COMPRESSION,