[PATCH 06/18] rhashtable: simplify nested_table_alloc() and rht_bucket_nested_insert()

NeilBrown
2018-06-01T04:44:09Z

Now that we don't use the hash value or shift in nested_table_alloc()
there is room for simplification.
We only need to pass a "is this a leaf" flag to nested_table_alloc(),
and don't need to track as much information in
rht_bucket_nested_insert().

Note there is another minor cleanup in nested_table_alloc() here.
The number of elements in a page of "union nested_tables" is most naturally

PAGE_SIZE / sizeof(ntbl[0])

The previous code had

PAGE_SIZE / sizeof(ntbl[0].bucket)

which happens to be the correct value only because the bucket uses all
the space in the union.

Signed-off-by: NeilBrown <neilb@suse.com>
---
lib/rhashtable.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 8582e1916c2d..e209069f1d74 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -116,7 +116,7 @@ static void bucket_table_free_rcu(struct rcu_head *head)

static union nested_table *nested_table_alloc(struct rhashtable *ht,
union nested_table __rcu **prev,
- unsigned int shifted)
+ bool leaf)
{
union nested_table *ntbl;
int i;
@@ -127,8 +127,8 @@ static union nested_table *nested_table_alloc(struct rhashtable *ht,

ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC);

- if (ntbl && shifted) {
- for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0].bucket); i++)
+ if (ntbl && leaf) {
+ for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0]); i++)
INIT_RHT_NULLS_HEAD(ntbl[i].bucket);
}

@@ -155,7 +155,7 @@ static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
return NULL;

if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
- 0)) {
+ false)) {
kfree(tbl);
return NULL;
}
@@ -1209,24 +1209,18 @@ struct rhash_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
unsigned int index = hash & ((1 << tbl->nest) - 1);
unsigned int size = tbl->size >> tbl->nest;
union nested_table *ntbl;
- unsigned int shifted;
- unsigned int nhash;

ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
hash >>= tbl->nest;
- nhash = index;
- shifted = tbl->nest;
ntbl = nested_table_alloc(ht, &ntbl[index].table,
- size <= (1 << shift) ? shifted : 0);
+ size <= (1 << shift));

while (ntbl && size > (1 << shift)) {
index = hash & ((1 << shift) - 1);
size >>= shift;
hash >>= shift;
- nhash |= index << shifted;
- shifted += shift;
ntbl = nested_table_alloc(ht, &ntbl[index].table,
- size <= (1 << shift) ? shifted : 0);
+ size <= (1 << shift));
}

if (!ntbl)