tdb: don't free old recovery area when expanding if already at EOF.

[ccan] / ccan / tdb / transaction.c

diff --git a/ccan/tdb/transaction.c b/ccan/tdb/transaction.c
index 525e0642d2b6088bb92d1a4bfd1f8b1232d4a42f..e34dee05c6bd80d148e6965ba1908e9265d7b01a 100644 (file)
--- a/ccan/tdb/transaction.c
+++ b/ccan/tdb/transaction.c
@@ -653,7 +653,7 @@ static int tdb_recovery_allocate(struct tdb_context *tdb,
 {
        struct tdb_record rec;
        const struct tdb_methods *methods = tdb->transaction->io_methods;
-       tdb_off_t recovery_head;
+       tdb_off_t recovery_head, new_end;
 
        if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to read recovery head\n"));
@@ -676,6 +676,7 @@ static int tdb_recovery_allocate(struct tdb_context *tdb,
 
        *recovery_size = tdb_recovery_size(tdb);
 
+       /* Existing recovery area? */
        if (recovery_head != 0 && *recovery_size <= rec.rec_len) {
                /* it fits in the existing area */
                *recovery_max_size = rec.rec_len;
@@ -683,33 +684,45 @@ static int tdb_recovery_allocate(struct tdb_context *tdb,
                return 0;
        }
 
-       /* we need to free up the old recovery area, then allocate a
-          new one at the end of the file. Note that we cannot use
-          tdb_allocate() to allocate the new one as that might return
-          us an area that is being currently used (as of the start of
-          the transaction) */
-       if (recovery_head != 0) {
-               if (tdb_free(tdb, recovery_head, &rec) == -1) {
-                       TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to free previous recovery area\n"));
-                       return -1;
+       /* If recovery area in middle of file, we need a new one. */
+       if (recovery_head == 0
+           || recovery_head + sizeof(rec) + rec.rec_len != tdb->map_size) {
+               /* we need to free up the old recovery area, then allocate a
+                  new one at the end of the file. Note that we cannot use
+                  tdb_allocate() to allocate the new one as that might return
+                  us an area that is being currently used (as of the start of
+                  the transaction) */
+               if (recovery_head) {
+                       if (tdb_free(tdb, recovery_head, &rec) == -1) {
+                               TDB_LOG((tdb, TDB_DEBUG_FATAL,
+                                        "tdb_recovery_allocate: failed to"
+                                        " free previous recovery area\n"));
+                               return -1;
+                       }
+
+                       /* the tdb_free() call might have increased
+                        * the recovery size */
+                       *recovery_size = tdb_recovery_size(tdb);
                }
+
+               /* New head will be at end of file. */
+               recovery_head = tdb->map_size;
        }
 
-       /* the tdb_free() call might have increased the recovery size */
-       *recovery_size = tdb_recovery_size(tdb);
+       /* Now we know where it will be. */
+       *recovery_offset = recovery_head;
 
-       /* round up to a multiple of page size */
+       /* Expand by more than we need, so we don't do it often. */
        *recovery_max_size = tdb_expand_adjust(tdb->map_size,
                                               *recovery_size,
                                               tdb->page_size)
                - sizeof(rec);
 
-       *recovery_offset = tdb->map_size;
-       recovery_head = *recovery_offset;
+       new_end = recovery_head + sizeof(rec) + *recovery_max_size;
 
        if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size, 
-                                    (tdb->map_size - tdb->transaction->old_map_size) +
-                                    sizeof(rec) + *recovery_max_size) == -1) {
+                                    new_end - tdb->transaction->old_map_size)
+           == -1) {
                TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_recovery_allocate: failed to create recovery area\n"));
                return -1;
        }