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 // SPDX-License-Identifier: GPL-2.0
 /*
  * tracing_map - lock-free map for tracing
  *
  * Copyright (C) 2015 Tom Zanussi <tom.zanussi@linux.intel.com>
  *
  * tracing_map implementation inspired by lock-free map algorithms
  * originated by Dr. Cliff Click:
  *
  * http://www.azulsystems.com/blog/cliff/2007-03-26-non-blocking-hashtable
  * http://www.azulsystems.com/events/javaone_2007/2007_LockFreeHash.pdf
  */
 
 #include <linux/vmalloc.h>
 #include <linux/jhash.h>
 #include <linux/slab.h>
 #include <linux/sort.h>
 #include <linux/kmemleak.h>
 
 #include "tracing_map.h"
 #include "trace.h"
 
 /*
  * NOTE: For a detailed description of the data structures used by
  * these functions (such as tracing_map_elt) please see the overview
  * of tracing_map data structures at the beginning of tracing_map.h.
  */
 
 /**
  * tracing_map_update_sum - Add a value to a tracing_map_elt's sum field
  * @elt: The tracing_map_elt
  * @i: The index of the given sum associated with the tracing_map_elt
  * @n: The value to add to the sum
  *
  * Add n to sum i associated with the specified tracing_map_elt
  * instance.  The index i is the index returned by the call to
  * tracing_map_add_sum_field() when the tracing map was set up.
  */
 void tracing_map_update_sum(struct tracing_map_elt *elt, unsigned int i, u64 n)
 {
     atomic64_add(n, &elt->fields[i].sum);
 }
 
 /**
  * tracing_map_read_sum - Return the value of a tracing_map_elt's sum field
  * @elt: The tracing_map_elt
  * @i: The index of the given sum associated with the tracing_map_elt
  *
  * Retrieve the value of the sum i associated with the specified
  * tracing_map_elt instance.  The index i is the index returned by the
  * call to tracing_map_add_sum_field() when the tracing map was set
  * up.
  *
  * Return: The sum associated with field i for elt.
  */
 u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i)
 {
     return (u64)atomic64_read(&elt->fields[i].sum);
 }
 
 /**
  * tracing_map_set_var - Assign a tracing_map_elt's variable field
  * @elt: The tracing_map_elt
  * @i: The index of the given variable associated with the tracing_map_elt
  * @n: The value to assign
  *
  * Assign n to variable i associated with the specified tracing_map_elt
  * instance.  The index i is the index returned by the call to
  * tracing_map_add_var() when the tracing map was set up.
  */
 void tracing_map_set_var(struct tracing_map_elt *elt, unsigned int i, u64 n)
 {
     atomic64_set(&elt->vars[i], n);
     elt->var_set[i] = true;
 }
 
 /**
  * tracing_map_var_set - Return whether or not a variable has been set
  * @elt: The tracing_map_elt
  * @i: The index of the given variable associated with the tracing_map_elt
  *
  * Return true if the variable has been set, false otherwise.  The
  * index i is the index returned by the call to tracing_map_add_var()
  * when the tracing map was set up.
  */
 bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i)
 {
     return elt->var_set[i];
 }
 
 /**
  * tracing_map_read_var - Return the value of a tracing_map_elt's variable field
  * @elt: The tracing_map_elt
  * @i: The index of the given variable associated with the tracing_map_elt
  *
  * Retrieve the value of the variable i associated with the specified
  * tracing_map_elt instance.  The index i is the index returned by the
  * call to tracing_map_add_var() when the tracing map was set
  * up.
  *
  * Return: The variable value associated with field i for elt.
  */
 u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i)
 {
     return (u64)atomic64_read(&elt->vars[i]);
 }
 
 /**
  * tracing_map_read_var_once - Return and reset a tracing_map_elt's variable field
  * @elt: The tracing_map_elt
  * @i: The index of the given variable associated with the tracing_map_elt
  *
  * Retrieve the value of the variable i associated with the specified
  * tracing_map_elt instance, and reset the variable to the 'not set'
  * state.  The index i is the index returned by the call to
  * tracing_map_add_var() when the tracing map was set up.  The reset
  * essentially makes the variable a read-once variable if it's only
  * accessed using this function.
  *
  * Return: The variable value associated with field i for elt.
  */
 u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i)
 {
     elt->var_set[i] = false;
     return (u64)atomic64_read(&elt->vars[i]);
 }
 
 int tracing_map_cmp_string(void *val_a, void *val_b)
 {
     char *a = val_a;
     char *b = val_b;
 
     return strcmp(a, b);
 }
 
 int tracing_map_cmp_none(void *val_a, void *val_b)
 {
     return 0;
 }
 
 static int tracing_map_cmp_atomic64(void *val_a, void *val_b)
 {
     u64 a = atomic64_read((atomic64_t *)val_a);
     u64 b = atomic64_read((atomic64_t *)val_b);
 
     return (a > b) ? 1 : ((a < b) ? -1 : 0);
 }
 
 #define DEFINE_TRACING_MAP_CMP_FN(type)                 \
 static int tracing_map_cmp_##type(void *val_a, void *val_b)     \
 {                                   \
     type a = (type)(*(u64 *)val_a);                 \
     type b = (type)(*(u64 *)val_b);                 \
                                     \
     return (a > b) ? 1 : ((a < b) ? -1 : 0);            \
 }
 
 DEFINE_TRACING_MAP_CMP_FN(s64);
 DEFINE_TRACING_MAP_CMP_FN(u64);
 DEFINE_TRACING_MAP_CMP_FN(s32);
 DEFINE_TRACING_MAP_CMP_FN(u32);
 DEFINE_TRACING_MAP_CMP_FN(s16);
 DEFINE_TRACING_MAP_CMP_FN(u16);
 DEFINE_TRACING_MAP_CMP_FN(s8);
 DEFINE_TRACING_MAP_CMP_FN(u8);
 
 tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
                      int field_is_signed)
 {
     tracing_map_cmp_fn_t fn = tracing_map_cmp_none;
 
     switch (field_size) {
     case 8:
         if (field_is_signed)
             fn = tracing_map_cmp_s64;
         else
             fn = tracing_map_cmp_u64;
         break;
     case 4:
         if (field_is_signed)
             fn = tracing_map_cmp_s32;
         else
             fn = tracing_map_cmp_u32;
         break;
     case 2:
         if (field_is_signed)
             fn = tracing_map_cmp_s16;
         else
             fn = tracing_map_cmp_u16;
         break;
     case 1:
         if (field_is_signed)
             fn = tracing_map_cmp_s8;
         else
             fn = tracing_map_cmp_u8;
         break;
     }
 
     return fn;
 }
 
 static int tracing_map_add_field(struct tracing_map *map,
                  tracing_map_cmp_fn_t cmp_fn)
 {
     int ret = -EINVAL;
 
     if (map->n_fields < TRACING_MAP_FIELDS_MAX) {
         ret = map->n_fields;
         map->fields[map->n_fields++].cmp_fn = cmp_fn;
     }
 
     return ret;
 }
 
 /**
  * tracing_map_add_sum_field - Add a field describing a tracing_map sum
  * @map: The tracing_map
  *
  * Add a sum field to the key and return the index identifying it in
  * the map and associated tracing_map_elts.  This is the index used
  * for instance to update a sum for a particular tracing_map_elt using
  * tracing_map_update_sum() or reading it via tracing_map_read_sum().
  *
  * Return: The index identifying the field in the map and associated
  * tracing_map_elts, or -EINVAL on error.
  */
 int tracing_map_add_sum_field(struct tracing_map *map)
 {
     return tracing_map_add_field(map, tracing_map_cmp_atomic64);
 }
 
 /**
  * tracing_map_add_var - Add a field describing a tracing_map var
  * @map: The tracing_map
  *
  * Add a var to the map and return the index identifying it in the map
  * and associated tracing_map_elts.  This is the index used for
  * instance to update a var for a particular tracing_map_elt using
  * tracing_map_update_var() or reading it via tracing_map_read_var().
  *
  * Return: The index identifying the var in the map and associated
  * tracing_map_elts, or -EINVAL on error.
  */
 int tracing_map_add_var(struct tracing_map *map)
 {
     int ret = -EINVAL;
 
     if (map->n_vars < TRACING_MAP_VARS_MAX)
         ret = map->n_vars++;
 
     return ret;
 }
 
 /**
  * tracing_map_add_key_field - Add a field describing a tracing_map key
  * @map: The tracing_map
  * @offset: The offset within the key
  * @cmp_fn: The comparison function that will be used to sort on the key
  *
  * Let the map know there is a key and that if it's used as a sort key
  * to use cmp_fn.
  *
  * A key can be a subset of a compound key; for that purpose, the
  * offset param is used to describe where within the compound key
  * the key referenced by this key field resides.
  *
  * Return: The index identifying the field in the map and associated
  * tracing_map_elts, or -EINVAL on error.
  */
 int tracing_map_add_key_field(struct tracing_map *map,
                   unsigned int offset,
                   tracing_map_cmp_fn_t cmp_fn)
 
 {
     int idx = tracing_map_add_field(map, cmp_fn);
 
     if (idx < 0)
         return idx;
 
     map->fields[idx].offset = offset;
 
     map->key_idx[map->n_keys++] = idx;
 
     return idx;
 }
 
 static void tracing_map_array_clear(struct tracing_map_array *a)
 {
     unsigned int i;
 
     if (!a->pages)
         return;
 
     for (i = 0; i < a->n_pages; i++)
         memset(a->pages[i], 0, PAGE_SIZE);
 }
 
 static void tracing_map_array_free(struct tracing_map_array *a)
 {
     unsigned int i;
 
     if (!a)
         return;
 
     if (!a->pages)
         goto free;
 
     for (i = 0; i < a->n_pages; i++) {
         if (!a->pages[i])
             break;
         kmemleak_free(a->pages[i]);
         free_page((unsigned long)a->pages[i]);
     }
 
     kfree(a->pages);
 
  free:
     kfree(a);
 }
 
 static struct tracing_map_array *tracing_map_array_alloc(unsigned int n_elts,
                           unsigned int entry_size)
 {
     struct tracing_map_array *a;
     unsigned int i;
 
     a = kzalloc(sizeof(*a), GFP_KERNEL);
     if (!a)
         return NULL;
 
     a->entry_size_shift = fls(roundup_pow_of_two(entry_size) - 1);
     a->entries_per_page = PAGE_SIZE / (1 << a->entry_size_shift);
     a->n_pages = n_elts / a->entries_per_page;
     if (!a->n_pages)
         a->n_pages = 1;
     a->entry_shift = fls(a->entries_per_page) - 1;
     a->entry_mask = (1 << a->entry_shift) - 1;
 
     a->pages = kcalloc(a->n_pages, sizeof(void *), GFP_KERNEL);
     if (!a->pages)
         goto free;
 
     for (i = 0; i < a->n_pages; i++) {
         a->pages[i] = (void *)get_zeroed_page(GFP_KERNEL);
         if (!a->pages[i])
             goto free;
         kmemleak_alloc(a->pages[i], PAGE_SIZE, 1, GFP_KERNEL);
     }
  out:
     return a;
  free:
     tracing_map_array_free(a);
     a = NULL;
 
     goto out;
 }
 
 static void tracing_map_elt_clear(struct tracing_map_elt *elt)
 {
     unsigned i;
 
     for (i = 0; i < elt->map->n_fields; i++)
         if (elt->fields[i].cmp_fn == tracing_map_cmp_atomic64)
             atomic64_set(&elt->fields[i].sum, 0);
 
     for (i = 0; i < elt->map->n_vars; i++) {
         atomic64_set(&elt->vars[i], 0);
         elt->var_set[i] = false;
     }
 
     if (elt->map->ops && elt->map->ops->elt_clear)
         elt->map->ops->elt_clear(elt);
 }
 
 static void tracing_map_elt_init_fields(struct tracing_map_elt *elt)
 {
     unsigned int i;
 
     tracing_map_elt_clear(elt);
 
     for (i = 0; i < elt->map->n_fields; i++) {
         elt->fields[i].cmp_fn = elt->map->fields[i].cmp_fn;
 
         if (elt->fields[i].cmp_fn != tracing_map_cmp_atomic64)
             elt->fields[i].offset = elt->map->fields[i].offset;
     }
 }
 
 static void tracing_map_elt_free(struct tracing_map_elt *elt)
 {
     if (!elt)
         return;
 
     if (elt->map->ops && elt->map->ops->elt_free)
         elt->map->ops->elt_free(elt);
     kfree(elt->fields);
     kfree(elt->vars);
     kfree(elt->var_set);
     kfree(elt->key);
     kfree(elt);
 }
 
 static struct tracing_map_elt *tracing_map_elt_alloc(struct tracing_map *map)
 {
     struct tracing_map_elt *elt;
     int err = 0;
 
     elt = kzalloc(sizeof(*elt), GFP_KERNEL);
     if (!elt)
         return ERR_PTR(-ENOMEM);
 
     elt->map = map;
 
     elt->key = kzalloc(map->key_size, GFP_KERNEL);
     if (!elt->key) {
         err = -ENOMEM;
         goto free;
     }
 
     elt->fields = kcalloc(map->n_fields, sizeof(*elt->fields), GFP_KERNEL);
     if (!elt->fields) {
         err = -ENOMEM;
         goto free;
     }
 
     elt->vars = kcalloc(map->n_vars, sizeof(*elt->vars), GFP_KERNEL);
     if (!elt->vars) {
         err = -ENOMEM;
         goto free;
     }
 
     elt->var_set = kcalloc(map->n_vars, sizeof(*elt->var_set), GFP_KERNEL);
     if (!elt->var_set) {
         err = -ENOMEM;
         goto free;
     }
 
     tracing_map_elt_init_fields(elt);
 
     if (map->ops && map->ops->elt_alloc) {
         err = map->ops->elt_alloc(elt);
         if (err)
             goto free;
     }
     return elt;
  free:
     tracing_map_elt_free(elt);
 
     return ERR_PTR(err);
 }
 
 static struct tracing_map_elt *get_free_elt(struct tracing_map *map)
 {
     struct tracing_map_elt *elt = NULL;
     int idx;
 
     idx = atomic_inc_return(&map->next_elt);
     if (idx < map->max_elts) {
         elt = *(TRACING_MAP_ELT(map->elts, idx));
         if (map->ops && map->ops->elt_init)
             map->ops->elt_init(elt);
     }
 
     return elt;
 }
 
 static void tracing_map_free_elts(struct tracing_map *map)
 {
     unsigned int i;
 
     if (!map->elts)
         return;
 
     for (i = 0; i < map->max_elts; i++) {
         tracing_map_elt_free(*(TRACING_MAP_ELT(map->elts, i)));
         *(TRACING_MAP_ELT(map->elts, i)) = NULL;
     }
 
     tracing_map_array_free(map->elts);
     map->elts = NULL;
 }
 
 static int tracing_map_alloc_elts(struct tracing_map *map)
 {
     unsigned int i;
 
     map->elts = tracing_map_array_alloc(map->max_elts,
                         sizeof(struct tracing_map_elt *));
     if (!map->elts)
         return -ENOMEM;
 
     for (i = 0; i < map->max_elts; i++) {
         *(TRACING_MAP_ELT(map->elts, i)) = tracing_map_elt_alloc(map);
         if (IS_ERR(*(TRACING_MAP_ELT(map->elts, i)))) {
             *(TRACING_MAP_ELT(map->elts, i)) = NULL;
             tracing_map_free_elts(map);
 
             return -ENOMEM;
         }
     }
 
     return 0;
 }
 
 static inline bool keys_match(void *key, void *test_key, unsigned key_size)
 {
     bool match = true;
 
     if (memcmp(key, test_key, key_size))
         match = false;
 
     return match;
 }
 
 static inline struct tracing_map_elt *
 __tracing_map_insert(struct tracing_map *map, void *key, bool lookup_only)
 {
     u32 idx, key_hash, test_key;
     int dup_try = 0;
     struct tracing_map_entry *entry;
     struct tracing_map_elt *val;
 
     key_hash = jhash(key, map->key_size, 0);
     if (key_hash == 0)
         key_hash = 1;
     idx = key_hash >> (32 - (map->map_bits + 1));
 
     while (1) {
         idx &= (map->map_size - 1);
         entry = TRACING_MAP_ENTRY(map->map, idx);
         test_key = entry->key;
 
         if (test_key && test_key == key_hash) {
             val = READ_ONCE(entry->val);
             if (val &&
                 keys_match(key, val->key, map->key_size)) {
                 if (!lookup_only)
                     atomic64_inc(&map->hits);
                 return val;
             } else if (unlikely(!val)) {
                 /*
                  * The key is present. But, val (pointer to elt
                  * struct) is still NULL. which means some other
                  * thread is in the process of inserting an
                  * element.
                  *
                  * On top of that, it's key_hash is same as the
                  * one being inserted right now. So, it's
                  * possible that the element has the same
                  * key as well.
                  */
 
                 dup_try++;
                 if (dup_try > map->map_size) {
                     atomic64_inc(&map->drops);
                     break;
                 }
                 continue;
             }
         }
 
         if (!test_key) {
             if (lookup_only)
                 break;
 
             if (!cmpxchg(&entry->key, 0, key_hash)) {
                 struct tracing_map_elt *elt;
 
                 elt = get_free_elt(map);
                 if (!elt) {
                     atomic64_inc(&map->drops);
                     entry->key = 0;
                     break;
                 }
 
                 memcpy(elt->key, key, map->key_size);
                 entry->val = elt;
                 atomic64_inc(&map->hits);
 
                 return entry->val;
             } else {
                 /*
                  * cmpxchg() failed. Loop around once
                  * more to check what key was inserted.
                  */
                 dup_try++;
                 continue;
             }
         }
 
         idx++;
     }
 
     return NULL;
 }
 
 /**
  * tracing_map_insert - Insert key and/or retrieve val from a tracing_map
  * @map: The tracing_map to insert into
  * @key: The key to insert
  *
  * Inserts a key into a tracing_map and creates and returns a new
  * tracing_map_elt for it, or if the key has already been inserted by
  * a previous call, returns the tracing_map_elt already associated
  * with it.  When the map was created, the number of elements to be
  * allocated for the map was specified (internally maintained as
  * 'max_elts' in struct tracing_map), and that number of
  * tracing_map_elts was created by tracing_map_init().  This is the
  * pre-allocated pool of tracing_map_elts that tracing_map_insert()
  * will allocate from when adding new keys.  Once that pool is
  * exhausted, tracing_map_insert() is useless and will return NULL to
  * signal that state.  There are two user-visible tracing_map
  * variables, 'hits' and 'drops', which are updated by this function.
  * Every time an element is either successfully inserted or retrieved,
  * the 'hits' value is incremented.  Every time an element insertion
  * fails, the 'drops' value is incremented.
  *
  * This is a lock-free tracing map insertion function implementing a
  * modified form of Cliff Click's basic insertion algorithm.  It
  * requires the table size be a power of two.  To prevent any
  * possibility of an infinite loop we always make the internal table
  * size double the size of the requested table size (max_elts * 2).
  * Likewise, we never reuse a slot or resize or delete elements - when
  * we've reached max_elts entries, we simply return NULL once we've
  * run out of entries.  Readers can at any point in time traverse the
  * tracing map and safely access the key/val pairs.
  *
  * Return: the tracing_map_elt pointer val associated with the key.
  * If this was a newly inserted key, the val will be a newly allocated
  * and associated tracing_map_elt pointer val.  If the key wasn't
  * found and the pool of tracing_map_elts has been exhausted, NULL is
  * returned and no further insertions will succeed.
  */
 struct tracing_map_elt *tracing_map_insert(struct tracing_map *map, void *key)
 {
     return __tracing_map_insert(map, key, false);
 }
 
 /**
  * tracing_map_lookup - Retrieve val from a tracing_map
  * @map: The tracing_map to perform the lookup on
  * @key: The key to look up
  *
  * Looks up key in tracing_map and if found returns the matching
  * tracing_map_elt.  This is a lock-free lookup; see
  * tracing_map_insert() for details on tracing_map and how it works.
  * Every time an element is retrieved, the 'hits' value is
  * incremented.  There is one user-visible tracing_map variable,
  * 'hits', which is updated by this function.  Every time an element
  * is successfully retrieved, the 'hits' value is incremented.  The
  * 'drops' value is never updated by this function.
  *
  * Return: the tracing_map_elt pointer val associated with the key.
  * If the key wasn't found, NULL is returned.
  */
 struct tracing_map_elt *tracing_map_lookup(struct tracing_map *map, void *key)
 {
     return __tracing_map_insert(map, key, true);
 }
 
 /**
  * tracing_map_destroy - Destroy a tracing_map
  * @map: The tracing_map to destroy
  *
  * Frees a tracing_map along with its associated array of
  * tracing_map_elts.
  *
  * Callers should make sure there are no readers or writers actively
  * reading or inserting into the map before calling this.
  */
 void tracing_map_destroy(struct tracing_map *map)
 {
     if (!map)
         return;
 
     tracing_map_free_elts(map);
 
     tracing_map_array_free(map->map);
     kfree(map);
 }
 
 /**
  * tracing_map_clear - Clear a tracing_map
  * @map: The tracing_map to clear
  *
  * Resets the tracing map to a cleared or initial state.  The
  * tracing_map_elts are all cleared, and the array of struct
  * tracing_map_entry is reset to an initialized state.
  *
  * Callers should make sure there are no writers actively inserting
  * into the map before calling this.
  */
 void tracing_map_clear(struct tracing_map *map)
 {
     unsigned int i;
 
     atomic_set(&map->next_elt, -1);
     atomic64_set(&map->hits, 0);
     atomic64_set(&map->drops, 0);
 
     tracing_map_array_clear(map->map);
 
     for (i = 0; i < map->max_elts; i++)
         tracing_map_elt_clear(*(TRACING_MAP_ELT(map->elts, i)));
 }
 
 static void set_sort_key(struct tracing_map *map,
              struct tracing_map_sort_key *sort_key)
 {
     map->sort_key = *sort_key;
 }
 
 /**
  * tracing_map_create - Create a lock-free map and element pool
  * @map_bits: The size of the map (2 ** map_bits)
  * @key_size: The size of the key for the map in bytes
  * @ops: Optional client-defined tracing_map_ops instance
  * @private_data: Client data associated with the map
  *
  * Creates and sets up a map to contain 2 ** map_bits number of
  * elements (internally maintained as 'max_elts' in struct
  * tracing_map).  Before using, map fields should be added to the map
  * with tracing_map_add_sum_field() and tracing_map_add_key_field().
  * tracing_map_init() should then be called to allocate the array of
  * tracing_map_elts, in order to avoid allocating anything in the map
  * insertion path.  The user-specified map size reflects the maximum
  * number of elements that can be contained in the table requested by
  * the user - internally we double that in order to keep the table
  * sparse and keep collisions manageable.
  *
  * A tracing_map is a special-purpose map designed to aggregate or
  * 'sum' one or more values associated with a specific object of type
  * tracing_map_elt, which is attached by the map to a given key.
  *
  * tracing_map_create() sets up the map itself, and provides
  * operations for inserting tracing_map_elts, but doesn't allocate the
  * tracing_map_elts themselves, or provide a means for describing the
  * keys or sums associated with the tracing_map_elts.  All
  * tracing_map_elts for a given map have the same set of sums and
  * keys, which are defined by the client using the functions
  * tracing_map_add_key_field() and tracing_map_add_sum_field().  Once
  * the fields are defined, the pool of elements allocated for the map
  * can be created, which occurs when the client code calls
  * tracing_map_init().
  *
  * When tracing_map_init() returns, tracing_map_elt elements can be
  * inserted into the map using tracing_map_insert().  When called,
  * tracing_map_insert() grabs a free tracing_map_elt from the pool, or
  * finds an existing match in the map and in either case returns it.
  * The client can then use tracing_map_update_sum() and
  * tracing_map_read_sum() to update or read a given sum field for the
  * tracing_map_elt.
  *
  * The client can at any point retrieve and traverse the current set
  * of inserted tracing_map_elts in a tracing_map, via
  * tracing_map_sort_entries().  Sorting can be done on any field,
  * including keys.
  *
  * See tracing_map.h for a description of tracing_map_ops.
  *
  * Return: the tracing_map pointer if successful, ERR_PTR if not.
  */
 struct tracing_map *tracing_map_create(unsigned int map_bits,
                        unsigned int key_size,
                        const struct tracing_map_ops *ops,
                        void *private_data)
 {
     struct tracing_map *map;
     unsigned int i;
 
     if (map_bits < TRACING_MAP_BITS_MIN ||
         map_bits > TRACING_MAP_BITS_MAX)
         return ERR_PTR(-EINVAL);
 
     map = kzalloc(sizeof(*map), GFP_KERNEL);
     if (!map)
         return ERR_PTR(-ENOMEM);
 
     map->map_bits = map_bits;
     map->max_elts = (1 << map_bits);
     atomic_set(&map->next_elt, -1);
 
     map->map_size = (1 << (map_bits + 1));
     map->ops = ops;
 
     map->private_data = private_data;
 
     map->map = tracing_map_array_alloc(map->map_size,
                        sizeof(struct tracing_map_entry));
     if (!map->map)
         goto free;
 
     map->key_size = key_size;
     for (i = 0; i < TRACING_MAP_KEYS_MAX; i++)
         map->key_idx[i] = -1;
  out:
     return map;
  free:
     tracing_map_destroy(map);
     map = ERR_PTR(-ENOMEM);
 
     goto out;
 }
 
 /**
  * tracing_map_init - Allocate and clear a map's tracing_map_elts
  * @map: The tracing_map to initialize
  *
  * Allocates a clears a pool of tracing_map_elts equal to the
  * user-specified size of 2 ** map_bits (internally maintained as
  * 'max_elts' in struct tracing_map).  Before using, the map fields
  * should be added to the map with tracing_map_add_sum_field() and
  * tracing_map_add_key_field().  tracing_map_init() should then be
  * called to allocate the array of tracing_map_elts, in order to avoid
  * allocating anything in the map insertion path.  The user-specified
  * map size reflects the max number of elements requested by the user
  * - internally we double that in order to keep the table sparse and
  * keep collisions manageable.
  *
  * See tracing_map.h for a description of tracing_map_ops.
  *
  * Return: the tracing_map pointer if successful, ERR_PTR if not.
  */
 int tracing_map_init(struct tracing_map *map)
 {
     int err;
 
     if (map->n_fields < 2)
         return -EINVAL; /* need at least 1 key and 1 val */
 
     err = tracing_map_alloc_elts(map);
     if (err)
         return err;
 
     tracing_map_clear(map);
 
     return err;
 }
 
 static int cmp_entries_dup(const void *A, const void *B)
 {
     const struct tracing_map_sort_entry *a, *b;
     int ret = 0;
 
     a = *(const struct tracing_map_sort_entry **)A;
     b = *(const struct tracing_map_sort_entry **)B;
 
     if (memcmp(a->key, b->key, a->elt->map->key_size))
         ret = 1;
 
     return ret;
 }
 
 static int cmp_entries_sum(const void *A, const void *B)
 {
     const struct tracing_map_elt *elt_a, *elt_b;
     const struct tracing_map_sort_entry *a, *b;
     struct tracing_map_sort_key *sort_key;
     struct tracing_map_field *field;
     tracing_map_cmp_fn_t cmp_fn;
     void *val_a, *val_b;
     int ret = 0;
 
     a = *(const struct tracing_map_sort_entry **)A;
     b = *(const struct tracing_map_sort_entry **)B;
 
     elt_a = a->elt;
     elt_b = b->elt;
 
     sort_key = &elt_a->map->sort_key;
 
     field = &elt_a->fields[sort_key->field_idx];
     cmp_fn = field->cmp_fn;
 
     val_a = &elt_a->fields[sort_key->field_idx].sum;
     val_b = &elt_b->fields[sort_key->field_idx].sum;
 
     ret = cmp_fn(val_a, val_b);
     if (sort_key->descending)
         ret = -ret;
 
     return ret;
 }
 
 static int cmp_entries_key(const void *A, const void *B)
 {
     const struct tracing_map_elt *elt_a, *elt_b;
     const struct tracing_map_sort_entry *a, *b;
     struct tracing_map_sort_key *sort_key;
     struct tracing_map_field *field;
     tracing_map_cmp_fn_t cmp_fn;
     void *val_a, *val_b;
     int ret = 0;
 
     a = *(const struct tracing_map_sort_entry **)A;
     b = *(const struct tracing_map_sort_entry **)B;
 
     elt_a = a->elt;
     elt_b = b->elt;
 
     sort_key = &elt_a->map->sort_key;
 
     field = &elt_a->fields[sort_key->field_idx];
 
     cmp_fn = field->cmp_fn;
 
     val_a = elt_a->key + field->offset;
     val_b = elt_b->key + field->offset;
 
     ret = cmp_fn(val_a, val_b);
     if (sort_key->descending)
         ret = -ret;
 
     return ret;
 }
 
 static void destroy_sort_entry(struct tracing_map_sort_entry *entry)
 {
     if (!entry)
         return;
 
     if (entry->elt_copied)
         tracing_map_elt_free(entry->elt);
 
     kfree(entry);
 }
 
 /**
  * tracing_map_destroy_sort_entries - Destroy an array of sort entries
  * @entries: The entries to destroy
  * @n_entries: The number of entries in the array
  *
  * Destroy the elements returned by a tracing_map_sort_entries() call.
  */
 void tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries,
                       unsigned int n_entries)
 {
     unsigned int i;
 
     for (i = 0; i < n_entries; i++)
         destroy_sort_entry(entries[i]);
 
     vfree(entries);
 }
 
 static struct tracing_map_sort_entry *
 create_sort_entry(void *key, struct tracing_map_elt *elt)
 {
     struct tracing_map_sort_entry *sort_entry;
 
     sort_entry = kzalloc(sizeof(*sort_entry), GFP_KERNEL);
     if (!sort_entry)
         return NULL;
 
     sort_entry->key = key;
     sort_entry->elt = elt;
 
     return sort_entry;
 }
 
 static void detect_dups(struct tracing_map_sort_entry **sort_entries,
               int n_entries, unsigned int key_size)
 {
     unsigned int dups = 0, total_dups = 0;
     int i;
     void *key;
 
     if (n_entries < 2)
         return;
 
     sort(sort_entries, n_entries, sizeof(struct tracing_map_sort_entry *),
          (int (*)(const void *, const void *))cmp_entries_dup, NULL);
 
     key = sort_entries[0]->key;
     for (i = 1; i < n_entries; i++) {
         if (!memcmp(sort_entries[i]->key, key, key_size)) {
             dups++; total_dups++;
             continue;
         }
         key = sort_entries[i]->key;
         dups = 0;
     }
 
     WARN_ONCE(total_dups > 0,
           "Duplicates detected: %d\n", total_dups);
 }
 
 static bool is_key(struct tracing_map *map, unsigned int field_idx)
 {
     unsigned int i;
 
     for (i = 0; i < map->n_keys; i++)
         if (map->key_idx[i] == field_idx)
             return true;
     return false;
 }
 
 static void sort_secondary(struct tracing_map *map,
                const struct tracing_map_sort_entry **entries,
                unsigned int n_entries,
                struct tracing_map_sort_key *primary_key,
                struct tracing_map_sort_key *secondary_key)
 {
     int (*primary_fn)(const void *, const void *);
     int (*secondary_fn)(const void *, const void *);
     unsigned i, start = 0, n_sub = 1;
 
     if (is_key(map, primary_key->field_idx))
         primary_fn = cmp_entries_key;
     else
         primary_fn = cmp_entries_sum;
 
     if (is_key(map, secondary_key->field_idx))
         secondary_fn = cmp_entries_key;
     else
         secondary_fn = cmp_entries_sum;
 
     for (i = 0; i < n_entries - 1; i++) {
         const struct tracing_map_sort_entry **a = &entries[i];
         const struct tracing_map_sort_entry **b = &entries[i + 1];
 
         if (primary_fn(a, b) == 0) {
             n_sub++;
             if (i < n_entries - 2)
                 continue;
         }
 
         if (n_sub < 2) {
             start = i + 1;
             n_sub = 1;
             continue;
         }
 
         set_sort_key(map, secondary_key);
         sort(&entries[start], n_sub,
              sizeof(struct tracing_map_sort_entry *),
              (int (*)(const void *, const void *))secondary_fn, NULL);
         set_sort_key(map, primary_key);
 
         start = i + 1;
         n_sub = 1;
     }
 }
 
 /**
  * tracing_map_sort_entries - Sort the current set of tracing_map_elts in a map
  * @map: The tracing_map
  * @sort_keys: The sort key to use for sorting
  * @n_sort_keys: hitcount, always have at least one
  * @sort_entries: outval: pointer to allocated and sorted array of entries
  *
  * tracing_map_sort_entries() sorts the current set of entries in the
  * map and returns the list of tracing_map_sort_entries containing
  * them to the client in the sort_entries param.  The client can
  * access the struct tracing_map_elt element of interest directly as
  * the 'elt' field of a returned struct tracing_map_sort_entry object.
  *
  * The sort_key has only two fields: idx and descending.  'idx' refers
  * to the index of the field added via tracing_map_add_sum_field() or
  * tracing_map_add_key_field() when the tracing_map was initialized.
  * 'descending' is a flag that if set reverses the sort order, which
  * by default is ascending.
  *
  * The client should not hold on to the returned array but should use
  * it and call tracing_map_destroy_sort_entries() when done.
  *
  * Return: the number of sort_entries in the struct tracing_map_sort_entry
  * array, negative on error
  */
 int tracing_map_sort_entries(struct tracing_map *map,
                  struct tracing_map_sort_key *sort_keys,
                  unsigned int n_sort_keys,
                  struct tracing_map_sort_entry ***sort_entries)
 {
     int (*cmp_entries_fn)(const void *, const void *);
     struct tracing_map_sort_entry *sort_entry, **entries;
     int i, n_entries, ret;
 
     entries = vmalloc(array_size(sizeof(sort_entry), map->max_elts));
     if (!entries)
         return -ENOMEM;
 
     for (i = 0, n_entries = 0; i < map->map_size; i++) {
         struct tracing_map_entry *entry;
 
         entry = TRACING_MAP_ENTRY(map->map, i);
 
         if (!entry->key || !entry->val)
             continue;
 
         entries[n_entries] = create_sort_entry(entry->val->key,
                                entry->val);
         if (!entries[n_entries++]) {
             ret = -ENOMEM;
             goto free;
         }
     }
 
     if (n_entries == 0) {
         ret = 0;
         goto free;
     }
 
     if (n_entries == 1) {
         *sort_entries = entries;
         return 1;
     }
 
     detect_dups(entries, n_entries, map->key_size);
 
     if (is_key(map, sort_keys[0].field_idx))
         cmp_entries_fn = cmp_entries_key;
     else
         cmp_entries_fn = cmp_entries_sum;
 
     set_sort_key(map, &sort_keys[0]);
 
     sort(entries, n_entries, sizeof(struct tracing_map_sort_entry *),
          (int (*)(const void *, const void *))cmp_entries_fn, NULL);
 
     if (n_sort_keys > 1)
         sort_secondary(map,
                    (const struct tracing_map_sort_entry **)entries,
                    n_entries,
                    &sort_keys[0],
                    &sort_keys[1]);
 
     *sort_entries = entries;
 
     return n_entries;
  free:
     tracing_map_destroy_sort_entries(entries, n_entries);
 
     return ret;
 }

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