Re: [PATCH 2/6] lib/rhashtable: guarantee initial hashtable allocation

[Davidlohr Bueso]

On Mon, 28 May 2018, Herbert Xu wrote:

On Thu, May 24, 2018 at 02:11:31PM -0700, Davidlohr Bueso wrote:

+       /*
+        * This is api initialization and thus we need to guarantee the
+        * initial rhashtable allocation. Upon failure, retry with a
+        * smallest possible size, otherwise we exhaust our options with
+        * __GFP_NOFAIL.
+        */
        tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
-       if (tbl == NULL)
-               return -ENOMEM;
+       if (unlikely(tbl == NULL)) {
+               size = HASH_MIN_SIZE;

You should also take min_size into account.  Yes I know the current
code ignores it unless you also set nelem_hint.  But that's just a
bug.

For the sake of simplicity, Linus suggested directly using HASH_MIN_SIZE
such that we have a single fallback.

Thanks,
Davidlohr