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-rw-r--r--e2fsprogs/ext2fs/sparse.c78
1 files changed, 78 insertions, 0 deletions
diff --git a/e2fsprogs/ext2fs/sparse.c b/e2fsprogs/ext2fs/sparse.c
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index 0000000..90b028f
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+++ b/e2fsprogs/ext2fs/sparse.c
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+/*
+ * sparse.c --- find the groups in an ext2 filesystem with metadata backups
+ *
+ * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
+ * Copyright (C) 2002 Andreas Dilger.
+ *
+ * %Begin-Header%
+ * This file may be redistributed under the terms of the GNU Public
+ * License.
+ * %End-Header%
+ */
+
+#include <stdio.h>
+
+#include "ext2_fs.h"
+#include "ext2fsP.h"
+
+static int test_root(int a, int b)
+{
+ if (a == 0)
+ return 1;
+ while (1) {
+ if (a == 1)
+ return 1;
+ if (a % b)
+ return 0;
+ a = a / b;
+ }
+}
+
+int ext2fs_bg_has_super(ext2_filsys fs, int group_block)
+{
+ if (!(fs->super->s_feature_ro_compat &
+ EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER))
+ return 1;
+
+ if (test_root(group_block, 3) || (test_root(group_block, 5)) ||
+ test_root(group_block, 7))
+ return 1;
+
+ return 0;
+}
+
+/*
+ * Iterate through the groups which hold BACKUP superblock/GDT copies in an
+ * ext3 filesystem. The counters should be initialized to 1, 5, and 7 before
+ * calling this for the first time. In a sparse filesystem it will be the
+ * sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ...
+ * For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ...
+ */
+unsigned int ext2fs_list_backups(ext2_filsys fs, unsigned int *three,
+ unsigned int *five, unsigned int *seven)
+{
+ unsigned int *min = three;
+ int mult = 3;
+ unsigned int ret;
+
+ if (!(fs->super->s_feature_ro_compat &
+ EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) {
+ ret = *min;
+ *min += 1;
+ return ret;
+ }
+
+ if (*five < *min) {
+ min = five;
+ mult = 5;
+ }
+ if (*seven < *min) {
+ min = seven;
+ mult = 7;
+ }
+
+ ret = *min;
+ *min *= mult;
+
+ return ret;
+}