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 // SPDX-License-Identifier: GPL-2.0
 #ifndef __TRACING_MAP_H
 #define __TRACING_MAP_H
 
 #define TRACING_MAP_BITS_DEFAULT    11
 #define TRACING_MAP_BITS_MAX        17
 #define TRACING_MAP_BITS_MIN        7
 
 #define TRACING_MAP_KEYS_MAX        3
 #define TRACING_MAP_VALS_MAX        3
 #define TRACING_MAP_FIELDS_MAX      (TRACING_MAP_KEYS_MAX + \
                      TRACING_MAP_VALS_MAX)
 #define TRACING_MAP_VARS_MAX        16
 #define TRACING_MAP_SORT_KEYS_MAX   2
 
 typedef int (*tracing_map_cmp_fn_t) (void *val_a, void *val_b);
 
 /*
  * This is an overview of the tracing_map data structures and how they
  * relate to the tracing_map API.  The details of the algorithms
  * aren't discussed here - this is just a general overview of the data
  * structures and how they interact with the API.
  *
  * The central data structure of the tracing_map is an initially
  * zeroed array of struct tracing_map_entry (stored in the map field
  * of struct tracing_map).  tracing_map_entry is a very simple data
  * structure containing only two fields: a 32-bit unsigned 'key'
  * variable and a pointer named 'val'.  This array of struct
  * tracing_map_entry is essentially a hash table which will be
  * modified by a single function, tracing_map_insert(), but which can
  * be traversed and read by a user at any time (though the user does
  * this indirectly via an array of tracing_map_sort_entry - see the
  * explanation of that data structure in the discussion of the
  * sorting-related data structures below).
  *
  * The central function of the tracing_map API is
  * tracing_map_insert().  tracing_map_insert() hashes the
  * arbitrarily-sized key passed into it into a 32-bit unsigned key.
  * It then uses this key, truncated to the array size, as an index
  * into the array of tracing_map_entries.  If the value of the 'key'
  * field of the tracing_map_entry found at that location is 0, then
  * that entry is considered to be free and can be claimed, by
  * replacing the 0 in the 'key' field of the tracing_map_entry with
  * the new 32-bit hashed key.  Once claimed, that tracing_map_entry's
  * 'val' field is then used to store a unique element which will be
  * forever associated with that 32-bit hashed key in the
  * tracing_map_entry.
  *
  * That unique element now in the tracing_map_entry's 'val' field is
  * an instance of tracing_map_elt, where 'elt' in the latter part of
  * that variable name is short for 'element'.  The purpose of a
  * tracing_map_elt is to hold values specific to the particular
  * 32-bit hashed key it's associated with.  Things such as the unique
  * set of aggregated sums associated with the 32-bit hashed key, along
  * with a copy of the full key associated with the entry, and which
  * was used to produce the 32-bit hashed key.
  *
  * When tracing_map_create() is called to create the tracing map, the
  * user specifies (indirectly via the map_bits param, the details are
  * unimportant for this discussion) the maximum number of elements
  * that the map can hold (stored in the max_elts field of struct
  * tracing_map).  This is the maximum possible number of
  * tracing_map_entries in the tracing_map_entry array which can be
  * 'claimed' as described in the above discussion, and therefore is
  * also the maximum number of tracing_map_elts that can be associated
  * with the tracing_map_entry array in the tracing_map.  Because of
  * the way the insertion algorithm works, the size of the allocated
  * tracing_map_entry array is always twice the maximum number of
  * elements (2 * max_elts).  This value is stored in the map_size
  * field of struct tracing_map.
  *
  * Because tracing_map_insert() needs to work from any context,
  * including from within the memory allocation functions themselves,
  * both the tracing_map_entry array and a pool of max_elts
  * tracing_map_elts are pre-allocated before any call is made to
  * tracing_map_insert().
  *
  * The tracing_map_entry array is allocated as a single block by
  * tracing_map_create().
  *
  * Because the tracing_map_elts are much larger objects and can't
  * generally be allocated together as a single large array without
  * failure, they're allocated individually, by tracing_map_init().
  *
  * The pool of tracing_map_elts are allocated by tracing_map_init()
  * rather than by tracing_map_create() because at the time
  * tracing_map_create() is called, there isn't enough information to
  * create the tracing_map_elts.  Specifically,the user first needs to
  * tell the tracing_map implementation how many fields the
  * tracing_map_elts contain, and which types of fields they are (key
  * or sum).  The user does this via the tracing_map_add_sum_field()
  * and tracing_map_add_key_field() functions, following which the user
  * calls tracing_map_init() to finish up the tracing map setup.  The
  * array holding the pointers which make up the pre-allocated pool of
  * tracing_map_elts is allocated as a single block and is stored in
  * the elts field of struct tracing_map.
  *
  * There is also a set of structures used for sorting that might
  * benefit from some minimal explanation.
  *
  * struct tracing_map_sort_key is used to drive the sort at any given
  * time.  By 'any given time' we mean that a different
  * tracing_map_sort_key will be used at different times depending on
  * whether the sort currently being performed is a primary or a
  * secondary sort.
  *
  * The sort key is very simple, consisting of the field index of the
  * tracing_map_elt field to sort on (which the user saved when adding
  * the field), and whether the sort should be done in an ascending or
  * descending order.
  *
  * For the convenience of the sorting code, a tracing_map_sort_entry
  * is created for each tracing_map_elt, again individually allocated
  * to avoid failures that might be expected if allocated as a single
  * large array of struct tracing_map_sort_entry.
  * tracing_map_sort_entry instances are the objects expected by the
  * various internal sorting functions, and are also what the user
  * ultimately receives after calling tracing_map_sort_entries().
  * Because it doesn't make sense for users to access an unordered and
  * sparsely populated tracing_map directly, the
  * tracing_map_sort_entries() function is provided so that users can
  * retrieve a sorted list of all existing elements.  In addition to
  * the associated tracing_map_elt 'elt' field contained within the
  * tracing_map_sort_entry, which is the object of interest to the
  * user, tracing_map_sort_entry objects contain a number of additional
  * fields which are used for caching and internal purposes and can
  * safely be ignored.
 */
 
 struct tracing_map_field {
     tracing_map_cmp_fn_t        cmp_fn;
     union {
         atomic64_t          sum;
         unsigned int            offset;
     };
 };
 
 struct tracing_map_elt {
     struct tracing_map      *map;
     struct tracing_map_field    *fields;
     atomic64_t          *vars;
     bool                *var_set;
     void                *key;
     void                *private_data;
 };
 
 struct tracing_map_entry {
     u32             key;
     struct tracing_map_elt      *val;
 };
 
 struct tracing_map_sort_key {
     unsigned int            field_idx;
     bool                descending;
 };
 
 struct tracing_map_sort_entry {
     void                *key;
     struct tracing_map_elt      *elt;
     bool                elt_copied;
     bool                dup;
 };
 
 struct tracing_map_array {
     unsigned int entries_per_page;
     unsigned int entry_size_shift;
     unsigned int entry_shift;
     unsigned int entry_mask;
     unsigned int n_pages;
     void **pages;
 };
 
 #define TRACING_MAP_ARRAY_ELT(array, idx)               \
     (array->pages[idx >> array->entry_shift] +          \
      ((idx & array->entry_mask) << array->entry_size_shift))
 
 #define TRACING_MAP_ENTRY(array, idx)                   \
     ((struct tracing_map_entry *)TRACING_MAP_ARRAY_ELT(array, idx))
 
 #define TRACING_MAP_ELT(array, idx)                 \
     ((struct tracing_map_elt **)TRACING_MAP_ARRAY_ELT(array, idx))
 
 struct tracing_map {
     unsigned int            key_size;
     unsigned int            map_bits;
     unsigned int            map_size;
     unsigned int            max_elts;
     atomic_t            next_elt;
     struct tracing_map_array    *elts;
     struct tracing_map_array    *map;
     const struct tracing_map_ops    *ops;
     void                *private_data;
     struct tracing_map_field    fields[TRACING_MAP_FIELDS_MAX];
     unsigned int            n_fields;
     int             key_idx[TRACING_MAP_KEYS_MAX];
     unsigned int            n_keys;
     struct tracing_map_sort_key sort_key;
     unsigned int            n_vars;
     atomic64_t          hits;
     atomic64_t          drops;
 };
 
 /**
  * struct tracing_map_ops - callbacks for tracing_map
  *
  * The methods in this structure define callback functions for various
  * operations on a tracing_map or objects related to a tracing_map.
  *
  * For a detailed description of tracing_map_elt objects please see
  * the overview of tracing_map data structures at the beginning of
  * this file.
  *
  * All the methods below are optional.
  *
  * @elt_alloc: When a tracing_map_elt is allocated, this function, if
  *  defined, will be called and gives clients the opportunity to
  *  allocate additional data and attach it to the element
  *  (tracing_map_elt->private_data is meant for that purpose).
  *  Element allocation occurs before tracing begins, when the
  *  tracing_map_init() call is made by client code.
  *
  * @elt_free: When a tracing_map_elt is freed, this function is called
  *  and allows client-allocated per-element data to be freed.
  *
  * @elt_clear: This callback allows per-element client-defined data to
  *  be cleared, if applicable.
  *
  * @elt_init: This callback allows per-element client-defined data to
  *  be initialized when used i.e. when the element is actually
  *  claimed by tracing_map_insert() in the context of the map
  *  insertion.
  */
 struct tracing_map_ops {
     int         (*elt_alloc)(struct tracing_map_elt *elt);
     void            (*elt_free)(struct tracing_map_elt *elt);
     void            (*elt_clear)(struct tracing_map_elt *elt);
     void            (*elt_init)(struct tracing_map_elt *elt);
 };
 
 extern struct tracing_map *
 tracing_map_create(unsigned int map_bits,
            unsigned int key_size,
            const struct tracing_map_ops *ops,
            void *private_data);
 extern int tracing_map_init(struct tracing_map *map);
 
 extern int tracing_map_add_sum_field(struct tracing_map *map);
 extern int tracing_map_add_var(struct tracing_map *map);
 extern int tracing_map_add_key_field(struct tracing_map *map,
                      unsigned int offset,
                      tracing_map_cmp_fn_t cmp_fn);
 
 extern void tracing_map_destroy(struct tracing_map *map);
 extern void tracing_map_clear(struct tracing_map *map);
 
 extern struct tracing_map_elt *
 tracing_map_insert(struct tracing_map *map, void *key);
 extern struct tracing_map_elt *
 tracing_map_lookup(struct tracing_map *map, void *key);
 
 extern tracing_map_cmp_fn_t tracing_map_cmp_num(int field_size,
                         int field_is_signed);
 extern int tracing_map_cmp_string(void *val_a, void *val_b);
 extern int tracing_map_cmp_none(void *val_a, void *val_b);
 
 extern void tracing_map_update_sum(struct tracing_map_elt *elt,
                    unsigned int i, u64 n);
 extern void tracing_map_set_var(struct tracing_map_elt *elt,
                 unsigned int i, u64 n);
 extern bool tracing_map_var_set(struct tracing_map_elt *elt, unsigned int i);
 extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i);
 extern u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i);
 extern u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i);
 
 extern void tracing_map_set_field_descr(struct tracing_map *map,
                     unsigned int i,
                     unsigned int key_offset,
                     tracing_map_cmp_fn_t cmp_fn);
 extern 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);
 
 extern void
 tracing_map_destroy_sort_entries(struct tracing_map_sort_entry **entries,
                  unsigned int n_entries);
 #endif /* __TRACING_MAP_H */

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