r23930: Introduce tdb_validate_and_backup:

This is a wrapper around tdb_validate, that does backup handling:

* if the given tdb is valid, a backup is created (name.bak)
* if the tdb is invalid, if a valid bakup is found (validated
  with the same validation function) under the name "name.bak"
  the orignal tdb is moved to name.corrupt and the backup
  is restored.

For the backup handling, a variant of the backup_tdb function
from lib/tdb/tools/tdbbackup.c is included in lib/util_tdb.c.
The copy function for the traverse action eliminates the need
to maintain a global success state by using a struct wrapping
the target tdb and a success flag as the private data.

Michael

diff --git a/source/lib/util_tdb.c b/source/lib/util_tdb.c
index 22831d97acefbf09fa50a21461b8159393f87b0a..7bba22f4bc9ee98e52112fe752da5b40a26d8fea 100644 (file)
--- a/source/lib/util_tdb.c
+++ b/source/lib/util_tdb.c
@@ -1044,6 +1044,9 @@ out:
        return ret;
 }
 
+/*
+ * tdb validation function returns 0 if tdb is ok, != 0 if it isn't.
+ */
 int tdb_validate(const char *tdb_path, tdb_validate_data_func validate_fn)
 {
        pid_t child_pid = -1;
@@ -1099,7 +1102,7 @@ int tdb_validate(const char *tdb_path, tdb_validate_data_func validate_fn)
                ret = WEXITSTATUS(child_status);
        }
        if (WIFSIGNALED(child_status)) {
-               DEBUG(10, ("tdb_validate: child terminated by signal %d\n", 
+               DEBUG(10, ("tdb_validate: child terminated by signal %d\n",
                           WTERMSIG(child_status)));
 #ifdef WCOREDUMP
                if (WCOREDUMP(child_status)) {
@@ -1119,3 +1122,238 @@ int tdb_validate(const char *tdb_path, tdb_validate_data_func validate_fn)
 
        return ret;
 }
+
+/*
+ * tdb backup function and helpers for tdb_validate wrapper with backup
+ * handling.
+ */
+
+/* this structure eliminates the need for a global overall status for
+ * the traverse-copy */
+struct tdb_copy_data {
+       struct tdb_context *dst;
+       BOOL success;
+};
+
+static int traverse_copy_fn(struct tdb_context *tdb, TDB_DATA key,
+                           TDB_DATA dbuf, void *private_data)
+{
+       struct tdb_copy_data *data = (struct tdb_copy_data *)private_data;
+
+       if (tdb_store(data->dst, key, dbuf, TDB_INSERT) != 0) {
+               DEBUG(4, ("Failed to insert into %s\n", tdb_name(data->dst)));
+               data->success = False;
+               return 1;
+       }
+       return 0;
+}
+
+static int tdb_copy(struct tdb_context *src, struct tdb_context *dst)
+{
+       struct tdb_copy_data data;
+       int count;
+
+       data.dst = dst;
+       data.success = True;
+
+       count = tdb_traverse(src, traverse_copy_fn, (void *)(&data));
+       if ((count < 0) || (data.success == False)) {
+               return -1;
+       }
+       return count;
+}
+
+static int tdb_verify_basic(struct tdb_context *tdb)
+{
+       return tdb_traverse(tdb, NULL, NULL);
+}
+
+/* this backup function is essentially taken from lib/tdb/tools/tdbbackup.tdb
+ */
+static int tdb_backup(TALLOC_CTX *ctx, const char *src_path,
+                     const char *dst_path, int hash_size)
+{
+       struct tdb_context *src_tdb = NULL;
+       struct tdb_context *dst_tdb = NULL;
+       char *tmp_path = NULL;
+       struct stat st;
+       int count1, count2;
+       int ret = -1;
+
+       if (stat(src_path, &st) != 0) {
+               DEBUG(3, ("Could not stat '%s': %s\n", src_path,
+                         strerror(errno)));
+               goto done;
+       }
+
+       /* open old tdb RDWR - so we can lock it */
+       src_tdb = tdb_open(src_path, 0, TDB_DEFAULT, O_RDWR, 0);
+       if (src_tdb == NULL) {
+               DEBUG(3, ("Failed to open tdb '%s'\n", src_path));
+               goto done;
+       }
+
+       if (tdb_lockall(src_tdb) != 0) {
+               DEBUG(3, ("Failed to lock tdb '%s'\n", src_path));
+               goto done;
+       }
+
+       tmp_path = talloc_asprintf(ctx, "%s%s", dst_path, ".tmp");
+       unlink(tmp_path);
+       dst_tdb = tdb_open(tmp_path,
+                          hash_size ? hash_size : tdb_hash_size(src_tdb),
+                          TDB_DEFAULT, O_RDWR | O_CREAT | O_EXCL,
+                          st.st_mode & 0777);
+       if (dst_tdb == NULL) {
+               DEBUG(3, ("Error creating tdb '%s': %s\n", tmp_path,
+                         strerror(errno)));
+               unlink(tmp_path);
+               goto done;
+       }
+
+       count1 = tdb_copy(src_tdb, dst_tdb);
+       if (count1 < 0) {
+               DEBUG(3, ("Failed to copy tdb '%s'\n", src_path));
+               tdb_close(dst_tdb);
+               goto done;
+       }
+
+       /* reopen ro and do basic verification */
+       tdb_close(dst_tdb);
+       dst_tdb = tdb_open(tmp_path, 0, TDB_DEFAULT, O_RDONLY, 0);
+       if (!dst_tdb) {
+               DEBUG(3, ("Failed to reopen tdb '%s': %s\n", tmp_path,
+                         strerror(errno)));
+               goto done;
+       }
+       count2 = tdb_verify_basic(dst_tdb);
+       if (count2 != count1) {
+               DEBUG(3, ("Failed to verify result of copying tdb '%s'.\n",
+                         src_path));
+               tdb_close(dst_tdb);
+               goto done;
+       }
+
+       /* make sure the new tdb has reached stable storage
+        * then rename it to its destination */
+       fsync(tdb_fd(dst_tdb));
+       tdb_close(dst_tdb);
+       unlink(dst_path);
+       if (rename(tmp_path, dst_path) != 0) {
+               DEBUG(3, ("Failed to rename '%s' to '%s': %s\n",
+                         tmp_path, dst_path, strerror(errno)));
+               goto done;
+       }
+
+       /* success */
+       ret = 0;
+
+done:
+       if (src_tdb != NULL) {
+               tdb_close(src_tdb);
+       }
+       if (tmp_path != NULL) {
+               unlink(tmp_path);
+               TALLOC_FREE(tmp_path);
+       }
+       return ret;
+}
+
+/*
+ * do a backup of a tdb, moving the destination out of the way first
+ */
+static int tdb_backup_with_rotate(TALLOC_CTX *ctx, const char *src_path,
+                                 const char *dst_path, int hash_size,
+                                 const char *rotate_suffix)
+{
+       char *rotate_path;
+       int ret = -1;
+
+       rotate_path = talloc_asprintf(ctx, "%s%s", dst_path, rotate_suffix);
+       if ((rename(dst_path, rotate_path) != 0) && (errno != ENOENT)) {
+               DEBUG(0, ("tdb_backup_with_rotate: error renaming "
+                         "%s to %s: %s\n", dst_path, rotate_path,
+                         strerror(errno)));
+               goto done;
+       }
+       ret = tdb_backup(ctx, src_path, dst_path, hash_size);
+
+done:
+       TALLOC_FREE(rotate_path);
+       return ret;
+}
+
+/*
+ * validation function with backup handling:
+ *
+ *  - calls tdb_validate
+ *  - if the tdb is ok, create a backup "name.bak", possibly moving
+ *    existing backup to name.bak.old
+ *  - if the tdb is corrupt, check if there is a valid backup.
+ *    if so, move corrupt tdb  to "name.corrupt",
+ *    and restore the backup
+ *    (give up if there is no backup or if it is invalid)
+ */
+int tdb_validate_and_backup(const char *tdb_path,
+                           tdb_validate_data_func validate_fn)
+{
+       int ret = -1;
+       const char *backup_suffix = ".bak";
+       const char *corrupt_suffix = ".corrupt";
+       const char *rotate_suffix = ".old";
+       char *tdb_path_backup;
+       struct stat st;
+       TALLOC_CTX *ctx = NULL;
+
+       ctx = talloc_new(NULL);
+       if (ctx == NULL) {
+               DEBUG(0, ("tdb_validate_and_backup: out of memory\n"));
+               goto done;
+       }
+
+       tdb_path_backup = talloc_asprintf(ctx, "%s%s", tdb_path, backup_suffix);
+
+       ret = tdb_validate(tdb_path, validate_fn);
+
+       if (ret == 0) {
+               DEBUG(1, ("tdb '%s' is valid\n", tdb_path));
+               ret = tdb_backup_with_rotate(ctx, tdb_path, tdb_path_backup, 0,
+                                            rotate_suffix);
+               if (ret != 0) {
+                       DEBUG(1, ("Error creating backup of tdb '%s'\n",
+                                 tdb_path));
+                       goto done;
+               }
+               DEBUG(1, ("Created backup '%s' of tdb '%s'\n", tdb_path_backup,
+                         tdb_path));
+       } else {
+               DEBUG(1, ("tdb '%s' is invalid\n", tdb_path));
+               if (stat(tdb_path_backup, &st) != 0) {
+                       DEBUG(3, ("Could not stat '%s': %s\n", tdb_path_backup,
+                                 strerror(errno)));
+                       DEBUG(1, ("No backup found. Giving up.\n"));
+                       goto done;
+               }
+               ret = tdb_validate(tdb_path_backup, validate_fn);
+               if (ret != 0) {
+                       DEBUG(1, ("Backup '%s' found but it is invalid.\n",
+                                 tdb_path_backup));
+                       goto done;
+               }
+               DEBUG(1, ("valid backup '%s' found\n", tdb_path_backup));
+               ret = tdb_backup_with_rotate(ctx, tdb_path_backup, tdb_path, 0,
+                                            corrupt_suffix);
+               if (ret != 0) {
+                       DEBUG(1, ("Error restoring backup from '%s'\n",
+                                 tdb_path_backup));
+                       goto done;
+               }
+               DEBUG(1, ("Restored tdb backup from '%s'\n", tdb_path_backup));
+               DEBUGADD(1, ("Corrupt tdb stored as '%s%s'\n", tdb_path,
+                            corrupt_suffix));
+       }
+
+done:
+       TALLOC_FREE(ctx);
+       return ret;
+}