> On Jun 23, 2022, at 7:51 PM, Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote:
>
>> On Jun 23, 2022, at 6:56 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>>
>> On Wed, Jun 22, 2022 at 10:15:50AM -0400, Chuck Lever wrote:
>>
>>> +static u32 nfsd_file_obj_hashfn(const void *data, u32 len, u32 seed)
>>> +{
>>> + const struct nfsd_file *nf = data;
>>> +
>>> + return jhash2((const u32 *)&nf->nf_inode,
>>> + sizeof_field(struct nfsd_file, nf_inode) / sizeof(u32),
>>> + seed);
>>
>> Out of curiosity - what are you using to allocate those? Because if
>> it's a slab, then middle bits of address (i.e. lower bits of
>> (unsigned long)data / L1_CACHE_BYTES) would better be random enough...
>
> 261 static struct nfsd_file *
> 262 nfsd_file_alloc(struct nfsd_file_lookup_key *key, unsigned int may)
> 263 {
> 264 static atomic_t nfsd_file_id;
> 265 struct nfsd_file *nf;
> 266
> 267 nf = kmem_cache_alloc(nfsd_file_slab, GFP_KERNEL);
>
> Was wondering about that. pahole says struct nfsd_file is 112
> bytes on my system.
Oops. nfsd_file_obj_hashfn() is supposed to be generating the
hash value based on the address stored in the nf_inode field.
So it's an inode pointer, alloced via kmem_cache_alloc by default.
--
Chuck Lever
