Trim SDS free space of retained module strings

In some cases processMultibulkBuffer uses sdsMakeRoomFor to
expand the querybuf, but later in some cases it uses that query
buffer as is for an argv element (see "Optimization"), which means
that the sds in argv may have a lot of wasted space, and then in case
modules keep that argv RedisString inside their data structure, this
space waste will remain for long (until restarted from rdb).

1 files changed, 4 insertions, 0 deletions

diff --git a/src/sds.c b/src/sds.c
index 330c955e8..cd60946bd 100644
--- a/src/sds.c
+++ b/src/sds.c
@@ -257,8 +257,12 @@ sds sdsRemoveFreeSpace(sds s) {
     char type, oldtype = s[-1] & SDS_TYPE_MASK;
     int hdrlen, oldhdrlen = sdsHdrSize(oldtype);
     size_t len = sdslen(s);
+    size_t avail = sdsavail(s);
     sh = (char*)s-oldhdrlen;
 
+    /* Return ASAP if there is no space left. */
+    if (avail == 0) return s;
+
     /* Check what would be the minimum SDS header that is just good enough to
      * fit this string. */
     type = sdsReqType(len);