/* SPDX-License-Identifier: GPL-2.0 */
/*
 * KUnit resource API for test managed resources (allocations, etc.).
 *
 * Copyright (C) 2022, Google LLC.
 * Author: Daniel Latypov <dlatypov@google.com>
 */

#ifndef _KUNIT_RESOURCE_H
#define _KUNIT_RESOURCE_H

#include <kunit/test.h>

#include <linux/kref.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

struct kunit_resource;

typedef int (*kunit_resource_init_t)(struct kunit_resource *, void *);
typedef void (*kunit_resource_free_t)(struct kunit_resource *);

/**
 * struct kunit_resource - represents a *test managed resource*
 * @data: for the user to store arbitrary data.
 * @name: optional name
 * @free: a user supplied function to free the resource.
 *
 * Represents a *test managed resource*, a resource which will automatically be
 * cleaned up at the end of a test case. This cleanup is performed by the 'free'
 * function. The struct kunit_resource itself is freed automatically with
 * kfree() if it was allocated by KUnit (e.g., by kunit_alloc_resource()), but
 * must be freed by the user otherwise.
 *
 * Resources are reference counted so if a resource is retrieved via
 * kunit_alloc_and_get_resource() or kunit_find_resource(), we need
 * to call kunit_put_resource() to reduce the resource reference count
 * when finished with it.  Note that kunit_alloc_resource() does not require a
 * kunit_resource_put() because it does not retrieve the resource itself.
 *
 * Example:
 *
 * .. code-block:: c
 *
 *      struct kunit_kmalloc_params {
 *              size_t size;
 *              gfp_t gfp;
 *      };
 *
 *      static int kunit_kmalloc_init(struct kunit_resource *res, void *context)
 *      {
 *              struct kunit_kmalloc_params *params = context;
 *              res->data = kmalloc(params->size, params->gfp);
 *
 *              if (!res->data)
 *                      return -ENOMEM;
 *
 *              return 0;
 *      }
 *
 *      static void kunit_kmalloc_free(struct kunit_resource *res)
 *      {
 *              kfree(res->data);
 *      }
 *
 *      void *kunit_kmalloc(struct kunit *test, size_t size, gfp_t gfp)
 *      {
 *              struct kunit_kmalloc_params params;
 *
 *              params.size = size;
 *              params.gfp = gfp;
 *
 *              return kunit_alloc_resource(test, kunit_kmalloc_init,
 *                      kunit_kmalloc_free, &params);
 *      }
 *
 * Resources can also be named, with lookup/removal done on a name
 * basis also.  kunit_add_named_resource(), kunit_find_named_resource()
 * and kunit_destroy_named_resource().  Resource names must be
 * unique within the test instance.
 */
struct kunit_resource {
        void *data;
        const char *name;
        kunit_resource_free_t free;

        /* private: internal use only. */
        struct kref refcount;
        struct list_head node;
        bool should_kfree;
};

/**
 * kunit_get_resource() - Hold resource for use.  Should not need to be used
 *                        by most users as we automatically get resources
 *                        retrieved by kunit_find_resource*().
 * @res: resource
 */
static inline void kunit_get_resource(struct kunit_resource *res)
{
        kref_get(&res->refcount);
}

/*
 * Called when refcount reaches zero via kunit_put_resource();
 * should not be called directly.
 */
static inline void kunit_release_resource(struct kref *kref)
{
        struct kunit_resource *res = container_of(kref, struct kunit_resource,
                                                  refcount);

        if (res->free)
                res->free(res);

        /* 'res' is valid here, as if should_kfree is set, res->free may not free
         * 'res' itself, just res->data
         */
        if (res->should_kfree)
                kfree(res);
}

/**
 * kunit_put_resource() - When caller is done with retrieved resource,
 *                        kunit_put_resource() should be called to drop
 *                        reference count.  The resource list maintains
 *                        a reference count on resources, so if no users
 *                        are utilizing a resource and it is removed from
 *                        the resource list, it will be freed via the
 *                        associated free function (if any).  Only
 *                        needs to be used if we alloc_and_get() or
 *                        find() resource.
 * @res: resource
 */
static inline void kunit_put_resource(struct kunit_resource *res)
{
        kref_put(&res->refcount, kunit_release_resource);
}

/**
 * __kunit_add_resource() - Internal helper to add a resource.
 *
 * res->should_kfree is not initialised.
 * @test: The test context object.
 * @init: a user-supplied function to initialize the result (if needed).  If
 *        none is supplied, the resource data value is simply set to @data.
 *        If an init function is supplied, @data is passed to it instead.
 * @free: a user-supplied function to free the resource (if needed).
 * @res: The resource.
 * @data: value to pass to init function or set in resource data field.
 */
int __kunit_add_resource(struct kunit *test,
                         kunit_resource_init_t init,
                         kunit_resource_free_t free,
                         struct kunit_resource *res,
                         void *data);

/**
 * kunit_add_resource() - Add a *test managed resource*.
 * @test: The test context object.
 * @init: a user-supplied function to initialize the result (if needed).  If
 *        none is supplied, the resource data value is simply set to @data.
 *        If an init function is supplied, @data is passed to it instead.
 * @free: a user-supplied function to free the resource (if needed).
 * @res: The resource.
 * @data: value to pass to init function or set in resource data field.
 */
static inline int kunit_add_resource(struct kunit *test,
                                     kunit_resource_init_t init,
                                     kunit_resource_free_t free,
                                     struct kunit_resource *res,
                                     void *data)
{
        res->should_kfree = false;
        return __kunit_add_resource(test, init, free, res, data);
}

static inline struct kunit_resource *
kunit_find_named_resource(struct kunit *test, const char *name);

/**
 * kunit_add_named_resource() - Add a named *test managed resource*.
 * @test: The test context object.
 * @init: a user-supplied function to initialize the resource data, if needed.
 * @free: a user-supplied function to free the resource data, if needed.
 * @res: The resource.
 * @name: name to be set for resource.
 * @data: value to pass to init function or set in resource data field.
 */
static inline int kunit_add_named_resource(struct kunit *test,
                                           kunit_resource_init_t init,
                                           kunit_resource_free_t free,
                                           struct kunit_resource *res,
                                           const char *name,
                                           void *data)
{
        struct kunit_resource *existing;

        if (!name)
                return -EINVAL;

        existing = kunit_find_named_resource(test, name);
        if (existing) {
                kunit_put_resource(existing);
                return -EEXIST;
        }

        res->name = name;
        res->should_kfree = false;

        return __kunit_add_resource(test, init, free, res, data);
}

/**
 * kunit_alloc_and_get_resource() - Allocates and returns a *test managed resource*.
 * @test: The test context object.
 * @init: a user supplied function to initialize the resource.
 * @free: a user supplied function to free the resource (if needed).
 * @internal_gfp: gfp to use for internal allocations, if unsure, use GFP_KERNEL
 * @context: for the user to pass in arbitrary data to the init function.
 *
 * Allocates a *test managed resource*, a resource which will automatically be
 * cleaned up at the end of a test case. See &struct kunit_resource for an
 * example.
 *
 * This is effectively identical to kunit_alloc_resource, but returns the
 * struct kunit_resource pointer, not just the 'data' pointer. It therefore
 * also increments the resource's refcount, so kunit_put_resource() should be
 * called when you've finished with it.
 *
 * Note: KUnit needs to allocate memory for a kunit_resource object. You must
 * specify an @internal_gfp that is compatible with the use context of your
 * resource.
 */
static inline struct kunit_resource *
kunit_alloc_and_get_resource(struct kunit *test,
                             kunit_resource_init_t init,
                             kunit_resource_free_t free,
                             gfp_t internal_gfp,
                             void *context)
{
        struct kunit_resource *res;
        int ret;

        res = kzalloc(sizeof(*res), internal_gfp);
        if (!res)
                return NULL;

        res->should_kfree = true;

        ret = __kunit_add_resource(test, init, free, res, context);
        if (!ret) {
                /*
                 * bump refcount for get; kunit_resource_put() should be called
                 * when done.
                 */
                kunit_get_resource(res);
                return res;
        }
        return NULL;
}

/**
 * kunit_alloc_resource() - Allocates a *test managed resource*.
 * @test: The test context object.
 * @init: a user supplied function to initialize the resource.
 * @free: a user supplied function to free the resource (if needed).
 * @internal_gfp: gfp to use for internal allocations, if unsure, use GFP_KERNEL
 * @context: for the user to pass in arbitrary data to the init function.
 *
 * Allocates a *test managed resource*, a resource which will automatically be
 * cleaned up at the end of a test case. See &struct kunit_resource for an
 * example.
 *
 * Note: KUnit needs to allocate memory for a kunit_resource object. You must
 * specify an @internal_gfp that is compatible with the use context of your
 * resource.
 */
static inline void *kunit_alloc_resource(struct kunit *test,
                                         kunit_resource_init_t init,
                                         kunit_resource_free_t free,
                                         gfp_t internal_gfp,
                                         void *context)
{
        struct kunit_resource *res;

        res = kzalloc(sizeof(*res), internal_gfp);
        if (!res)
                return NULL;

        res->should_kfree = true;
        if (!__kunit_add_resource(test, init, free, res, context))
                return res->data;

        return NULL;
}

typedef bool (*kunit_resource_match_t)(struct kunit *test,
                                       struct kunit_resource *res,
                                       void *match_data);

/**
 * kunit_resource_instance_match() - Match a resource with the same instance.
 * @test: Test case to which the resource belongs.
 * @res: The resource.
 * @match_data: The resource pointer to match against.
 *
 * An instance of kunit_resource_match_t that matches a resource whose
 * allocation matches @match_data.
 */
static inline bool kunit_resource_instance_match(struct kunit *test,
                                                 struct kunit_resource *res,
                                                 void *match_data)
{
        return res->data == match_data;
}

/**
 * kunit_resource_name_match() - Match a resource with the same name.
 * @test: Test case to which the resource belongs.
 * @res: The resource.
 * @match_name: The name to match against.
 */
static inline bool kunit_resource_name_match(struct kunit *test,
                                             struct kunit_resource *res,
                                             void *match_name)
{
        return res->name && strcmp(res->name, match_name) == 0;
}

/**
 * kunit_find_resource() - Find a resource using match function/data.
 * @test: Test case to which the resource belongs.
 * @match: match function to be applied to resources/match data.
 * @match_data: data to be used in matching.
 */
static inline struct kunit_resource *
kunit_find_resource(struct kunit *test,
                    kunit_resource_match_t match,
                    void *match_data)
{
        struct kunit_resource *res, *found = NULL;
        unsigned long flags;

        spin_lock_irqsave(&test->lock, flags);

        list_for_each_entry_reverse(res, &test->resources, node) {
                if (match(test, res, (void *)match_data)) {
                        found = res;
                        kunit_get_resource(found);
                        break;
                }
        }

        spin_unlock_irqrestore(&test->lock, flags);

        return found;
}

/**
 * kunit_find_named_resource() - Find a resource using match name.
 * @test: Test case to which the resource belongs.
 * @name: match name.
 */
static inline struct kunit_resource *
kunit_find_named_resource(struct kunit *test,
                          const char *name)
{
        return kunit_find_resource(test, kunit_resource_name_match,
                                   (void *)name);
}

/**
 * kunit_destroy_resource() - Find a kunit_resource and destroy it.
 * @test: Test case to which the resource belongs.
 * @match: Match function. Returns whether a given resource matches @match_data.
 * @match_data: Data passed into @match.
 *
 * RETURNS:
 * 0 if kunit_resource is found and freed, -ENOENT if not found.
 */
int kunit_destroy_resource(struct kunit *test,
                           kunit_resource_match_t match,
                           void *match_data);

static inline int kunit_destroy_named_resource(struct kunit *test,
                                               const char *name)
{
        return kunit_destroy_resource(test, kunit_resource_name_match,
                                      (void *)name);
}

/**
 * kunit_remove_resource() - remove resource from resource list associated with
 *                           test.
 * @test: The test context object.
 * @res: The resource to be removed.
 *
 * Note that the resource will not be immediately freed since it is likely
 * the caller has a reference to it via alloc_and_get() or find();
 * in this case a final call to kunit_put_resource() is required.
 */
void kunit_remove_resource(struct kunit *test, struct kunit_resource *res);

#endif /* _KUNIT_RESOURCE_H */