qht: constify qht_lookup

seqlock_read_begin takes a const param since c04649e
("seqlock: constify seqlock_read_begin", 2018-08-23), so
we can constify the entire lookup.

Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

include/qemu/qht.h

@@ -104,7 +104,7 @@ bool qht_insert(struct qht *ht, void *p, uint32_t hash, void **existing);
  * Returns the corresponding pointer when a match is found.
  * Returns NULL otherwise.
  */
-void *qht_lookup_custom(struct qht *ht, const void *userp, uint32_t hash,
+void *qht_lookup_custom(const struct qht *ht, const void *userp, uint32_t hash,
                         qht_lookup_func_t func);
 
 /**
@@ -115,7 +115,7 @@ void *qht_lookup_custom(struct qht *ht, const void *userp, uint32_t hash,
  *
  * Calls qht_lookup_custom() using @ht's default comparison function.
  */
-void *qht_lookup(struct qht *ht, const void *userp, uint32_t hash);
+void *qht_lookup(const struct qht *ht, const void *userp, uint32_t hash);
 
 /**
  * qht_remove - remove a pointer from the hash table

util/qht.c

@@ -236,7 +236,7 @@ static inline void qht_head_init(struct qht_bucket *b)
 }
 
 static inline
-struct qht_bucket *qht_map_to_bucket(struct qht_map *map, uint32_t hash)
+struct qht_bucket *qht_map_to_bucket(const struct qht_map *map, uint32_t hash)
 {
     return &map->buckets[hash & (map->n_buckets - 1)];
 }
@@ -482,10 +482,10 @@ bool qht_reset_size(struct qht *ht, size_t n_elems)
 }
 
 static inline
-void *qht_do_lookup(struct qht_bucket *head, qht_lookup_func_t func,
+void *qht_do_lookup(const struct qht_bucket *head, qht_lookup_func_t func,
                     const void *userp, uint32_t hash)
 {
-    struct qht_bucket *b = head;
+    const struct qht_bucket *b = head;
     int i;
 
     do {
@@ -509,7 +509,7 @@ void *qht_do_lookup(struct qht_bucket *head, qht_lookup_func_t func,
 }
 
 static __attribute__((noinline))
-void *qht_lookup__slowpath(struct qht_bucket *b, qht_lookup_func_t func,
+void *qht_lookup__slowpath(const struct qht_bucket *b, qht_lookup_func_t func,
                            const void *userp, uint32_t hash)
 {
     unsigned int version;
@@ -522,11 +522,11 @@ void *qht_lookup__slowpath(struct qht_bucket *b, qht_lookup_func_t func,
     return ret;
 }
 
-void *qht_lookup_custom(struct qht *ht, const void *userp, uint32_t hash,
+void *qht_lookup_custom(const struct qht *ht, const void *userp, uint32_t hash,
                         qht_lookup_func_t func)
 {
-    struct qht_bucket *b;
-    struct qht_map *map;
+    const struct qht_bucket *b;
+    const struct qht_map *map;
     unsigned int version;
     void *ret;
 
@@ -545,7 +545,7 @@ void *qht_lookup_custom(struct qht *ht, const void *userp, uint32_t hash,
     return qht_lookup__slowpath(b, func, userp, hash);
 }
 
-void *qht_lookup(struct qht *ht, const void *userp, uint32_t hash)
+void *qht_lookup(const struct qht *ht, const void *userp, uint32_t hash)
 {
     return qht_lookup_custom(ht, userp, hash, ht->cmp);
 }