MINOR: chunks: Add function to get a large/regular chunk depending on a buffer

get_best_trash_chunk() function was added to be able to get a large or a
regular chunk depending on a given size but never larget than a given
buffer. It will be usefull in a futur fix, to prevent unexpected large chunk
usage.

alloc_best_trash_chunk() function is similar but instead of returning one of
the static chunks, it allocate it from the corresponding pool, large or
regular.

include/haproxy/chunk.h

@@ -51,6 +51,7 @@ struct buffer *get_trash_chunk(void);
 struct buffer *get_large_trash_chunk(void);
 struct buffer *get_small_trash_chunk(void);
 struct buffer *get_trash_chunk_sz(size_t size);
+struct buffer *get_best_trash_chunk(const struct buffer *buf, size_t size);
 struct buffer *get_larger_trash_chunk(struct buffer *chunk);
 int init_trash_buffers(int first);
 
@@ -172,6 +173,21 @@ static forceinline struct buffer *alloc_trash_chunk_sz(size_t size)
 	else
 		return NULL;
 }
+/* Returns a trash chunk accordingly to the requested size and never larger
+ * that the buffer <buf>. So if <buf> is a large buffer,
+ * alloc_trash_chunk_sz() function is called. Otherwise, if the size is
+ * smaller enough, a regular buffer is allocated. If <size> is too big and
+ * <buf> is not a large buffer, NULL is returned.
+ */
+static forceinline struct buffer *alloc_best_trash_chunk(const struct buffer *buf, size_t size)
+{
+	if (pool_head_large_trash && buf->size == pool_head_large_trash->size)
+		return alloc_trash_chunk_sz(size);
+	else if (size <= pool_head_trash->size)
+		return alloc_trash_chunk();
+	else
+		return NULL;
+}
 
 /*
  * free a trash chunk allocated by alloc_trash_chunk(). NOP on NULL.

src/chunk.c

@@ -160,6 +160,22 @@ struct buffer *get_trash_chunk_sz(size_t size)
 		return NULL;
 }
 
+/* Returns a trash chunk accordingly to the requested size and never larger
+ * that the buffer <buf>. So if <buf> is a large buffer,
+ * get_trash_chunk_sz() function is called. Otherwise, if the size is
+ * smaller enough, a regular buffer is returned. If <size> is too big and
+ * <buf> is not a large buffer, NULL is returned.
+ */
+struct buffer *get_best_trash_chunk(const struct buffer *buf, size_t size)
+{
+	if (large_trash_size && buf->size == large_trash_size)
+		return get_trash_chunk_sz(size);
+	else if (size <= trash_size)
+		return get_trash_chunk();
+	else
+		return NULL;
+}
+
 /* Returns a larger buffer than <chk> if possible or NULL otherwise. If a larger
  * buffer is returned, content of <chk> are copied.
  */