Re: [PATCH v2] lib/hash: new feature adding existing key

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 16 Feb 2024 13:43:52 +0100
Thomas Monjalon <thomas@monjalon.net> wrote:

> Any review please?
> If maintainers agree with the idea, we should announce the ABI change.
> 
> 
> 23/10/2023 10:29, Abdullah Ömer Yamaç:
> > From: Abdullah Ömer Yamaç <omer.yamac@ceng.metu.edu.tr>
> > 
> > In some use cases inserting data with the same key shouldn't be
> > overwritten. We use a new flag in this patch to disable overwriting
> > data for the same key.
> > 
> > Signed-off-by: Abdullah Ömer Yamaç <omer.yamac@ceng.metu.edu.tr>
> > 
> > ---
> > Cc: Yipeng Wang <yipeng1.wang@intel.com>
> > Cc: Sameh Gobriel <sameh.gobriel@intel.com>
> > Cc: Bruce Richardson <bruce.richardson@intel.com>
> > Cc: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
> > Cc: David Marchand <david.marchand@redhat.com>
> > ---
> >  lib/hash/rte_cuckoo_hash.c | 10 +++++++++-
> >  lib/hash/rte_cuckoo_hash.h |  2 ++
> >  lib/hash/rte_hash.h        |  4 ++++
> >  3 files changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/lib/hash/rte_cuckoo_hash.c b/lib/hash/rte_cuckoo_hash.c
> > index 19b23f2a97..fe8f21bee4 100644
> > --- a/lib/hash/rte_cuckoo_hash.c
> > +++ b/lib/hash/rte_cuckoo_hash.c
> > @@ -32,7 +32,8 @@
> >  				   RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY | \
> >  				   RTE_HASH_EXTRA_FLAGS_EXT_TABLE |	\
> >  				   RTE_HASH_EXTRA_FLAGS_NO_FREE_ON_DEL | \
> > -				   RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF)
> > +				   RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF | \
> > +				   RTE_HASH_EXTRA_FLAGS_DISABLE_UPDATE_EXISTING_KEY)
> >  
> >  #define FOR_EACH_BUCKET(CURRENT_BKT, START_BUCKET)                            \
> >  	for (CURRENT_BKT = START_BUCKET;                                      \
> > @@ -148,6 +149,7 @@ rte_hash_create(const struct rte_hash_parameters *params)
> >  	unsigned int readwrite_concur_support = 0;
> >  	unsigned int writer_takes_lock = 0;
> >  	unsigned int no_free_on_del = 0;
> > +	unsigned int no_update_data = 0;
> >  	uint32_t *ext_bkt_to_free = NULL;
> >  	uint32_t *tbl_chng_cnt = NULL;
> >  	struct lcore_cache *local_free_slots = NULL;
> > @@ -216,6 +218,9 @@ rte_hash_create(const struct rte_hash_parameters *params)
> >  		no_free_on_del = 1;
> >  	}
> >  
> > +	if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_DISABLE_UPDATE_EXISTING_KEY)
> > +		no_update_data = 1;
> > +
> >  	/* Store all keys and leave the first entry as a dummy entry for lookup_bulk */
> >  	if (use_local_cache)
> >  		/*
> > @@ -428,6 +433,7 @@ rte_hash_create(const struct rte_hash_parameters *params)
> >  	h->ext_table_support = ext_table_support;
> >  	h->writer_takes_lock = writer_takes_lock;
> >  	h->no_free_on_del = no_free_on_del;
> > +	h->no_update_data = no_update_data;
> >  	h->readwrite_concur_lf_support = readwrite_concur_lf_support;
> >  
> >  #if defined(RTE_ARCH_X86)
> > @@ -707,6 +713,8 @@ search_and_update(const struct rte_hash *h, void *data, const void *key,
> >  			k = (struct rte_hash_key *) ((char *)keys +
> >  					bkt->key_idx[i] * h->key_entry_size);
> >  			if (rte_hash_cmp_eq(key, k->key, h) == 0) {
> > +				if (h->no_update_data == 1)
> > +					return -EINVAL;

This is buggy, the caller assumes -1 on error in several places.
See:
	ret = search_and_update(h, data, key, prim_bkt, sig);
	if (ret != -1) {
		__hash_rw_writer_unlock(h);
		*ret_val = ret;
		return 1;
	}
These paths would exercised when table had to expand.

Also any new functionality like this would need tests in functional test.