From: Willy Tarreau <w@1wt.eu>
Date: Fri, 31 Dec 2021 15:00:19 +0000 (+0100)
Subject: CLEANUP: pools: do not use the extra pointer to link shared elements
X-Git-Tag: v2.6-dev1~205
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=799f6143ca2a0a7ff8979ae5850b462363d76437;p=thirdparty%2Fhaproxy.git

CLEANUP: pools: do not use the extra pointer to link shared elements

This practice relying on POOL_LINK() dates from the era where there were
no pool caches, but given that the structures are a bit more complex now
and that pool caches do not make use of this feature, it is totally
useless since released elements have already been overwritten, and yet
it complicates the architecture and prevents from making simplifications
and optimizations. Let's just get rid of this feature. The pointer to
the origin pool is preserved though, as it helps detect incorrect frees
and serves as a canary for overflows.
---

diff --git a/include/haproxy/pool-t.h b/include/haproxy/pool-t.h
index 48d06be151..d476f31d4f 100644
--- a/include/haproxy/pool-t.h
+++ b/include/haproxy/pool-t.h
@@ -40,7 +40,6 @@
 #define POOL_LINK(pool, item) (void **)(((char *)(item)) + ((pool)->size))
 #else
 #define POOL_EXTRA (0)
-#define POOL_LINK(pool, item) ((void **)(item))
 #endif
 
 /* A special pointer for the pool's free_list that indicates someone is
diff --git a/include/haproxy/pool.h b/include/haproxy/pool.h
index cb2c8b4de2..d8407b19ec 100644
--- a/include/haproxy/pool.h
+++ b/include/haproxy/pool.h
@@ -132,7 +132,7 @@ static inline void *pool_get_from_shared_cache(struct pool_head *pool)
 	}
 
 	/* this releases the lock */
-	_HA_ATOMIC_STORE(&pool->free_list, *POOL_LINK(pool, ret));
+	_HA_ATOMIC_STORE(&pool->free_list, *(void **)ret);
 	_HA_ATOMIC_INC(&pool->used);
 
 #ifdef DEBUG_MEMORY_POOLS
@@ -164,7 +164,7 @@ static inline void pool_put_to_shared_cache(struct pool_head *pool, void *ptr)
 				__ha_cpu_relax();
 				free_list = _HA_ATOMIC_LOAD(&pool->free_list);
 			}
-			_HA_ATOMIC_STORE(POOL_LINK(pool, ptr), (void *)free_list);
+			_HA_ATOMIC_STORE((void **)ptr, (void *)free_list);
 			__ha_barrier_atomic_store();
 		} while (!_HA_ATOMIC_CAS(&pool->free_list, &free_list, ptr));
 		__ha_barrier_atomic_store();
diff --git a/src/pool.c b/src/pool.c
index e64bfcacf0..7d83a953f9 100644
--- a/src/pool.c
+++ b/src/pool.c
@@ -417,7 +417,7 @@ void pool_flush(struct pool_head *pool)
 
 	while (next) {
 		temp = next;
-		next = *POOL_LINK(pool, temp);
+		next = *(void **)temp;
 		pool_put_to_os(pool, temp);
 	}
 	/* here, we should have pool->allocated == pool->used */
@@ -442,7 +442,7 @@ void pool_gc(struct pool_head *pool_ctx)
 		while (entry->free_list &&
 		       (int)(entry->allocated - entry->used) > (int)entry->minavail) {
 			temp = entry->free_list;
-			entry->free_list = *POOL_LINK(entry, temp);
+			entry->free_list = *(void **)temp;
 			pool_put_to_os(entry, temp);
 		}
 	}