mem: fix f_malloc big fragments search

In some situation (depending on previous allocation and frees)
trying to allocate a "big" fragment (>16k) would fail even if
enough memory was available (the fragment search algorithm missed
fallback to bigger buckets when using the free bitmap).
(cherry picked from commit 1ccbd33558e7e09f36f39fd984ac99a7bfd3eba2)

mem/f_malloc.c

@@ -34,6 +34,12 @@
  *  2007-02-23  added fm_available() (andrei)
  *  2007-06-23  added hash bitmap (andrei)
  *  2009-09-28  added fm_sums() (patch from Dragos Vingarzan)
+ *  2010-03-11  fix big fragments bug (smaller fragment was wrongly
+ *               returned sometimes) (andrei)
+ *  2010-03-12  fix real_used stats for realloc: a realloc that shrank an
+ *               allocation accounted twice fro the frag. overhead (andrei)
+ *  2010-09-30  fixed search for big fragments using the hash bitmap
+ *               (only the first bucket was tried) (andrei)
  */
 
 
@@ -336,11 +342,23 @@ void* fm_malloc(struct fm_block* qm, unsigned long size)
 #ifdef F_MALLOC_HASH_BITMAP
 	hash=fm_bmp_first_set(qm, GET_HASH(size));
 	if (likely(hash>=0)){
-		f=&(qm->free_hash[hash].first);
-	if (likely(hash<=F_MALLOC_OPTIMIZE/ROUNDTO)) /* return first match */
-			goto found; 
-		for(;(*f); f=&((*f)->u.nxt_free))
-			if ((*f)->size>=size) goto found;
+		if (likely(hash<=F_MALLOC_OPTIMIZE/ROUNDTO)) { /* return first match */
+			f=&(qm->free_hash[hash].first);
+			goto found;
+		}
+		/* if we are here we are searching for a "big" fragment
+		   between F_MALLOC_OPTIMIZE/ROUNDTO+1
+		   and F_MALLOC_OPTIMIZE/ROUNDTO + (32|64) - F_MALLOC_OPTIMIZE_FACTOR
+		   => 18 hash buckets on 32 bits and 50 buckets on 64 bits
+		   The free hash bitmap is used to jump directly to non-empty
+		   hash buckets.
+		*/
+		do {
+			for(f=&(qm->free_hash[hash].first);(*f); f=&((*f)->u.nxt_free))
+				if ((*f)->size>=size) goto found;
+			hash++; /* try in next hash cell */
+		}while((hash < F_HASH_SIZE) &&
+				((hash=fm_bmp_first_set(qm, hash)) >= 0));
 	}
 #else /* F_MALLOC_HASH_BITMAP */
 	for(hash=GET_HASH(size);hash<F_HASH_SIZE;hash++){