tdb_expand: limit the expansion with huge records

ldb can create huge records when saving indexes.
Limit the tdb expansion to avoid consuming a lot of memory for
no good reason if the record being saved is huge.

Fix bug #7610 (winbindd_cache.tdb grows too large when scaled).

diff --git a/lib/tdb/common/io.c b/lib/tdb/common/io.c
index d549715f831b414fc098b334a97f6572c74ffc76..2f58a49058b08465589eb22362fb1616ff61f211 100644 (file)
--- a/lib/tdb/common/io.c
+++ b/lib/tdb/common/io.c
@@ -299,7 +299,7 @@ static int tdb_expand_file(struct tdb_context *tdb, tdb_off_t size, tdb_off_t ad
 int tdb_expand(struct tdb_context *tdb, tdb_off_t size)
 {
        struct tdb_record rec;
-       tdb_off_t offset, new_size;     
+       tdb_off_t offset, new_size, top_size, map_size;
 
        if (tdb_lock(tdb, -1, F_WRLCK) == -1) {
                TDB_LOG((tdb, TDB_DEBUG_ERROR, "lock failed in tdb_expand\n"));
@@ -309,10 +309,25 @@ int tdb_expand(struct tdb_context *tdb, tdb_off_t size)
        /* must know about any previous expansions by another process */
        tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1);
 
-       /* always make room for at least 100 more records, and at
-           least 25% more space. Round the database up to a multiple
-           of the page size */
-       new_size = MAX(tdb->map_size + size*100, tdb->map_size * 1.25);
+       /* limit size in order to avoid using up huge amounts of memory for
+        * in memory tdbs if an oddball huge record creeps in */
+       if (size > 100 * 1024) {
+               top_size = tdb->map_size + size * 2;
+       } else {
+               top_size = tdb->map_size + size * 100;
+       }
+
+       /* always make room for at least top_size more records, and at
+          least 25% more space. if the DB is smaller than 100MiB,
+          otherwise grow it by 10% only. */
+       if (tdb->map_size > 100 * 1024 * 1024) {
+               map_size = tdb->map_size * 1.10;
+       } else {
+               map_size = tdb->map_size * 1.25;
+       }
+
+       /* Round the database up to a multiple of the page size */
+       new_size = MAX(top_size, map_size);
        size = TDB_ALIGN(new_size, tdb->page_size) - tdb->map_size;
 
        if (!(tdb->flags & TDB_INTERNAL))