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rhashtable: Remove RCU marking from rhash_lock_head
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The opaque type rhash_lock_head should not be marked with __rcu
because it can never be dereferenced.  We should apply the RCU
marking when we turn it into a pointer which can be dereferenced.

This patch does exactly that.  This fixes a number of sparse
warnings as well as getting rid of some unnecessary RCU checking.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
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@herbertx @davem330
herbertx authored and davem330 committed May 16, 2019
1 parent c7d5ec2 commit ba6306e
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Showing 2 changed files with 46 additions and 40 deletions.
58 changes: 32 additions & 26 deletions include/linux/rhashtable.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -84,7 +84,7 @@ struct bucket_table {

struct lockdep_map dep_map;

struct rhash_lock_head __rcu *buckets[] ____cacheline_aligned_in_smp;
struct rhash_lock_head *buckets[] ____cacheline_aligned_in_smp;
};

/*
Expand Down Expand Up @@ -261,13 +261,13 @@ void rhashtable_free_and_destroy(struct rhashtable *ht,
void *arg);
void rhashtable_destroy(struct rhashtable *ht);

struct rhash_lock_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
unsigned int hash);
struct rhash_lock_head __rcu **__rht_bucket_nested(const struct bucket_table *tbl,
unsigned int hash);
struct rhash_lock_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
struct bucket_table *tbl,
unsigned int hash);
struct rhash_lock_head **rht_bucket_nested(const struct bucket_table *tbl,
unsigned int hash);
struct rhash_lock_head **__rht_bucket_nested(const struct bucket_table *tbl,
unsigned int hash);
struct rhash_lock_head **rht_bucket_nested_insert(struct rhashtable *ht,
struct bucket_table *tbl,
unsigned int hash);

#define rht_dereference(p, ht) \
rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
Expand All @@ -284,21 +284,21 @@ struct rhash_lock_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
#define rht_entry(tpos, pos, member) \
({ tpos = container_of(pos, typeof(*tpos), member); 1; })

static inline struct rhash_lock_head __rcu *const *rht_bucket(
static inline struct rhash_lock_head *const *rht_bucket(
const struct bucket_table *tbl, unsigned int hash)
{
return unlikely(tbl->nest) ? rht_bucket_nested(tbl, hash) :
&tbl->buckets[hash];
}

static inline struct rhash_lock_head __rcu **rht_bucket_var(
static inline struct rhash_lock_head **rht_bucket_var(
struct bucket_table *tbl, unsigned int hash)
{
return unlikely(tbl->nest) ? __rht_bucket_nested(tbl, hash) :
&tbl->buckets[hash];
}

static inline struct rhash_lock_head __rcu **rht_bucket_insert(
static inline struct rhash_lock_head **rht_bucket_insert(
struct rhashtable *ht, struct bucket_table *tbl, unsigned int hash)
{
return unlikely(tbl->nest) ? rht_bucket_nested_insert(ht, tbl, hash) :
Expand Down Expand Up @@ -349,37 +349,43 @@ static inline void rht_unlock(struct bucket_table *tbl,
local_bh_enable();
}

static inline struct rhash_head __rcu *__rht_ptr(
struct rhash_lock_head *const *bkt)
{
return (struct rhash_head __rcu *)((unsigned long)*bkt & ~BIT(0));
}

/*
* Where 'bkt' is a bucket and might be locked:
* rht_ptr() dereferences that pointer and clears the lock bit.
* rht_ptr_exclusive() dereferences in a context where exclusive
* access is guaranteed, such as when destroying the table.
*/
static inline struct rhash_head *rht_ptr(
struct rhash_lock_head __rcu * const *bkt,
struct rhash_lock_head *const *bkt,
struct bucket_table *tbl,
unsigned int hash)
{
const struct rhash_lock_head *p =
rht_dereference_bucket_rcu(*bkt, tbl, hash);
struct rhash_head __rcu *p = __rht_ptr(bkt);

if ((((unsigned long)p) & ~BIT(0)) == 0)
if (!p)
return RHT_NULLS_MARKER(bkt);
return (void *)(((unsigned long)p) & ~BIT(0));

return rht_dereference_bucket_rcu(p, tbl, hash);
}

static inline struct rhash_head *rht_ptr_exclusive(
struct rhash_lock_head __rcu * const *bkt)
struct rhash_lock_head *const *bkt)
{
const struct rhash_lock_head *p =
rcu_dereference_protected(*bkt, 1);
struct rhash_head __rcu *p = __rht_ptr(bkt);

if (!p)
return RHT_NULLS_MARKER(bkt);
return (void *)(((unsigned long)p) & ~BIT(0));

return rcu_dereference_protected(p, 1);
}

static inline void rht_assign_locked(struct rhash_lock_head __rcu **bkt,
static inline void rht_assign_locked(struct rhash_lock_head **bkt,
struct rhash_head *obj)
{
struct rhash_head __rcu **p = (struct rhash_head __rcu **)bkt;
Expand All @@ -390,7 +396,7 @@ static inline void rht_assign_locked(struct rhash_lock_head __rcu **bkt,
}

static inline void rht_assign_unlock(struct bucket_table *tbl,
struct rhash_lock_head __rcu **bkt,
struct rhash_lock_head **bkt,
struct rhash_head *obj)
{
struct rhash_head __rcu **p = (struct rhash_head __rcu **)bkt;
Expand Down Expand Up @@ -587,7 +593,7 @@ static inline struct rhash_head *__rhashtable_lookup(
.ht = ht,
.key = key,
};
struct rhash_lock_head __rcu * const *bkt;
struct rhash_lock_head *const *bkt;
struct bucket_table *tbl;
struct rhash_head *he;
unsigned int hash;
Expand Down Expand Up @@ -703,7 +709,7 @@ static inline void *__rhashtable_insert_fast(
.ht = ht,
.key = key,
};
struct rhash_lock_head __rcu **bkt;
struct rhash_lock_head **bkt;
struct rhash_head __rcu **pprev;
struct bucket_table *tbl;
struct rhash_head *head;
Expand Down Expand Up @@ -989,7 +995,7 @@ static inline int __rhashtable_remove_fast_one(
struct rhash_head *obj, const struct rhashtable_params params,
bool rhlist)
{
struct rhash_lock_head __rcu **bkt;
struct rhash_lock_head **bkt;
struct rhash_head __rcu **pprev;
struct rhash_head *he;
unsigned int hash;
Expand Down Expand Up @@ -1141,7 +1147,7 @@ static inline int __rhashtable_replace_fast(
struct rhash_head *obj_old, struct rhash_head *obj_new,
const struct rhashtable_params params)
{
struct rhash_lock_head __rcu **bkt;
struct rhash_lock_head **bkt;
struct rhash_head __rcu **pprev;
struct rhash_head *he;
unsigned int hash;
Expand Down
28 changes: 14 additions & 14 deletions lib/rhashtable.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@

union nested_table {
union nested_table __rcu *table;
struct rhash_lock_head __rcu *bucket;
struct rhash_lock_head *bucket;
};

static u32 head_hashfn(struct rhashtable *ht,
Expand Down Expand Up @@ -216,7 +216,7 @@ static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
}

static int rhashtable_rehash_one(struct rhashtable *ht,
struct rhash_lock_head __rcu **bkt,
struct rhash_lock_head **bkt,
unsigned int old_hash)
{
struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
Expand Down Expand Up @@ -269,7 +269,7 @@ static int rhashtable_rehash_chain(struct rhashtable *ht,
unsigned int old_hash)
{
struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
struct rhash_lock_head __rcu **bkt = rht_bucket_var(old_tbl, old_hash);
struct rhash_lock_head **bkt = rht_bucket_var(old_tbl, old_hash);
int err;

if (!bkt)
Expand Down Expand Up @@ -478,7 +478,7 @@ static int rhashtable_insert_rehash(struct rhashtable *ht,
}

static void *rhashtable_lookup_one(struct rhashtable *ht,
struct rhash_lock_head __rcu **bkt,
struct rhash_lock_head **bkt,
struct bucket_table *tbl, unsigned int hash,
const void *key, struct rhash_head *obj)
{
Expand Down Expand Up @@ -529,7 +529,7 @@ static void *rhashtable_lookup_one(struct rhashtable *ht,
}

static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
struct rhash_lock_head __rcu **bkt,
struct rhash_lock_head **bkt,
struct bucket_table *tbl,
unsigned int hash,
struct rhash_head *obj,
Expand Down Expand Up @@ -584,7 +584,7 @@ static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
{
struct bucket_table *new_tbl;
struct bucket_table *tbl;
struct rhash_lock_head __rcu **bkt;
struct rhash_lock_head **bkt;
unsigned int hash;
void *data;

Expand Down Expand Up @@ -1166,8 +1166,8 @@ void rhashtable_destroy(struct rhashtable *ht)
}
EXPORT_SYMBOL_GPL(rhashtable_destroy);

struct rhash_lock_head __rcu **__rht_bucket_nested(const struct bucket_table *tbl,
unsigned int hash)
struct rhash_lock_head **__rht_bucket_nested(const struct bucket_table *tbl,
unsigned int hash)
{
const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
unsigned int index = hash & ((1 << tbl->nest) - 1);
Expand Down Expand Up @@ -1195,20 +1195,20 @@ struct rhash_lock_head __rcu **__rht_bucket_nested(const struct bucket_table *tb
}
EXPORT_SYMBOL_GPL(__rht_bucket_nested);

struct rhash_lock_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
unsigned int hash)
struct rhash_lock_head **rht_bucket_nested(const struct bucket_table *tbl,
unsigned int hash)
{
static struct rhash_lock_head __rcu *rhnull;
static struct rhash_lock_head *rhnull;

if (!rhnull)
INIT_RHT_NULLS_HEAD(rhnull);
return __rht_bucket_nested(tbl, hash) ?: &rhnull;
}
EXPORT_SYMBOL_GPL(rht_bucket_nested);

struct rhash_lock_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
struct bucket_table *tbl,
unsigned int hash)
struct rhash_lock_head **rht_bucket_nested_insert(struct rhashtable *ht,
struct bucket_table *tbl,
unsigned int hash)
{
const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
unsigned int index = hash & ((1 << tbl->nest) - 1);
Expand Down

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