/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * include/linux/sunrpc/cache.h
 *
 * Generic code for various authentication-related caches
 * used by sunrpc clients and servers.
 *
 * Copyright (C) 2002 Neil Brown <neilb@cse.unsw.edu.au>
 */

#ifndef _LINUX_SUNRPC_CACHE_H_
#define _LINUX_SUNRPC_CACHE_H_

#include <linux/kref.h>
#include <linux/slab.h>
#include <linux/atomic.h>
#include <linux/kstrtox.h>
#include <linux/proc_fs.h>

/*
 * Each cache requires:
 *  - A 'struct cache_detail' which contains information specific to the cache
 *    for common code to use.
 *  - An item structure that must contain a "struct cache_head"
 *  - A lookup function defined using DefineCacheLookup
 *  - A 'put' function that can release a cache item. It will only
 *    be called after cache_put has succeed, so there are guarantee
 *    to be no references.
 *  - A function to calculate a hash of an item's key.
 *
 * as well as assorted code fragments (e.g. compare keys) and numbers
 * (e.g. hash size, goal_age, etc).
 *
 * Each cache must be registered so that it can be cleaned regularly.
 * When the cache is unregistered, it is flushed completely.
 *
 * Entries have a ref count and a 'hashed' flag which counts the existence
 * in the hash table.
 * We only expire entries when refcount is zero.
 * Existence in the cache is counted  the refcount.
 */

/* Every cache item has a common header that is used
 * for expiring and refreshing entries.
 * 
 */
struct cache_head {
        struct hlist_node       cache_list;
        time64_t        expiry_time;    /* After time expiry_time, don't use
                                         * the data */
        time64_t        last_refresh;   /* If CACHE_PENDING, this is when upcall was
                                         * sent, else this is when update was
                                         * received, though it is alway set to
                                         * be *after* ->flush_time.
                                         */
        struct kref     ref;
        unsigned long   flags;
};

/* cache_head.flags */
enum {
        CACHE_VALID,            /* Entry contains valid data */
        CACHE_NEGATIVE,         /* Negative entry - there is no match for the key */
        CACHE_PENDING,          /* An upcall has been sent but no reply received yet*/
        CACHE_CLEANED,          /* Entry has been cleaned from cache */
};

#define CACHE_NEW_EXPIRY 120    /* keep new things pending confirmation for 120 seconds */

struct cache_detail {
        struct module *         owner;
        int                     hash_size;
        struct hlist_head *     hash_table;
        spinlock_t              hash_lock;

        char                    *name;
        void                    (*cache_put)(struct kref *);

        int                     (*cache_upcall)(struct cache_detail *,
                                                struct cache_head *);

        void                    (*cache_request)(struct cache_detail *cd,
                                                 struct cache_head *ch,
                                                 char **bpp, int *blen);

        int                     (*cache_parse)(struct cache_detail *,
                                               char *buf, int len);

        int                     (*cache_show)(struct seq_file *m,
                                              struct cache_detail *cd,
                                              struct cache_head *h);
        void                    (*warn_no_listener)(struct cache_detail *cd,
                                              int has_died);

        struct cache_head *     (*alloc)(void);
        void                    (*flush)(void);
        int                     (*match)(struct cache_head *orig, struct cache_head *new);
        void                    (*init)(struct cache_head *orig, struct cache_head *new);
        void                    (*update)(struct cache_head *orig, struct cache_head *new);

        /* fields below this comment are for internal use
         * and should not be touched by cache owners
         */
        time64_t                flush_time;             /* flush all cache items with
                                                         * last_refresh at or earlier
                                                         * than this.  last_refresh
                                                         * is never set at or earlier
                                                         * than this.
                                                         */
        struct list_head        others;
        time64_t                nextcheck;
        int                     entries;

        /* fields for communication over channel */
        struct list_head        queue;

        atomic_t                writers;                /* how many time is /channel open */
        time64_t                last_close;             /* if no writers, when did last close */
        time64_t                last_warn;              /* when we last warned about no writers */

        union {
                struct proc_dir_entry   *procfs;
                struct dentry           *pipefs;
        };
        struct net              *net;
};

/* this must be embedded in any request structure that
 * identifies an object that will want a callback on
 * a cache fill
 */
struct cache_req {
        struct cache_deferred_req *(*defer)(struct cache_req *req);
        unsigned long   thread_wait;    /* How long (jiffies) we can block the
                                         * current thread to wait for updates.
                                         */
};

/* this must be embedded in a deferred_request that is being
 * delayed awaiting cache-fill
 */
struct cache_deferred_req {
        struct hlist_node       hash;   /* on hash chain */
        struct list_head        recent; /* on fifo */
        struct cache_head       *item;  /* cache item we wait on */
        void                    *owner; /* we might need to discard all defered requests
                                         * owned by someone */
        void                    (*revisit)(struct cache_deferred_req *req,
                                           int too_many);
};

/*
 * timestamps kept in the cache are expressed in seconds
 * since boot.  This is the best for measuring differences in
 * real time.
 * This reimplemnts ktime_get_boottime_seconds() in a slightly
 * faster but less accurate way. When we end up converting
 * back to wallclock (CLOCK_REALTIME), that error often
 * cancels out during the reverse operation.
 */
static inline time64_t seconds_since_boot(void)
{
        struct timespec64 boot;
        getboottime64(&boot);
        return ktime_get_real_seconds() - boot.tv_sec;
}

static inline time64_t convert_to_wallclock(time64_t sinceboot)
{
        struct timespec64 boot;
        getboottime64(&boot);
        return boot.tv_sec + sinceboot;
}

extern const struct file_operations cache_file_operations_pipefs;
extern const struct file_operations content_file_operations_pipefs;
extern const struct file_operations cache_flush_operations_pipefs;

extern struct cache_head *
sunrpc_cache_lookup_rcu(struct cache_detail *detail,
                        struct cache_head *key, int hash);
extern struct cache_head *
sunrpc_cache_update(struct cache_detail *detail,
                    struct cache_head *new, struct cache_head *old, int hash);

extern int
sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h);
extern int
sunrpc_cache_pipe_upcall_timeout(struct cache_detail *detail,
                                 struct cache_head *h);


extern void cache_clean_deferred(void *owner);

static inline struct cache_head  *cache_get(struct cache_head *h)
{
        kref_get(&h->ref);
        return h;
}

static inline struct cache_head  *cache_get_rcu(struct cache_head *h)
{
        if (kref_get_unless_zero(&h->ref))
                return h;
        return NULL;
}

static inline void cache_put(struct cache_head *h, struct cache_detail *cd)
{
        if (kref_read(&h->ref) <= 2 &&
            h->expiry_time < cd->nextcheck)
                cd->nextcheck = h->expiry_time;
        kref_put(&h->ref, cd->cache_put);
}

static inline bool cache_is_expired(struct cache_detail *detail, struct cache_head *h)
{
        if (h->expiry_time < seconds_since_boot())
                return true;
        if (!test_bit(CACHE_VALID, &h->flags))
                return false;
        return detail->flush_time >= h->last_refresh;
}

extern int cache_check_rcu(struct cache_detail *detail,
                       struct cache_head *h, struct cache_req *rqstp);
extern int cache_check(struct cache_detail *detail,
                       struct cache_head *h, struct cache_req *rqstp);
extern void cache_flush(void);
extern void cache_purge(struct cache_detail *detail);
#define NEVER (0x7FFFFFFF)
extern void __init cache_initialize(void);
extern int cache_register_net(struct cache_detail *cd, struct net *net);
extern void cache_unregister_net(struct cache_detail *cd, struct net *net);

extern struct cache_detail *cache_create_net(const struct cache_detail *tmpl, struct net *net);
extern void cache_destroy_net(struct cache_detail *cd, struct net *net);

extern void sunrpc_init_cache_detail(struct cache_detail *cd);
extern void sunrpc_destroy_cache_detail(struct cache_detail *cd);
extern int sunrpc_cache_register_pipefs(struct dentry *parent, const char *,
                                        umode_t, struct cache_detail *);
extern void sunrpc_cache_unregister_pipefs(struct cache_detail *);
extern void sunrpc_cache_unhash(struct cache_detail *, struct cache_head *);

/* Must store cache_detail in seq_file->private if using next three functions */
extern void *cache_seq_start_rcu(struct seq_file *file, loff_t *pos);
extern void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos);
extern void cache_seq_stop_rcu(struct seq_file *file, void *p);

extern void qword_add(char **bpp, int *lp, char *str);
extern void qword_addhex(char **bpp, int *lp, char *buf, int blen);
extern int qword_get(char **bpp, char *dest, int bufsize);

static inline int get_int(char **bpp, int *anint)
{
        char buf[50];
        char *ep;
        int rv;
        int len = qword_get(bpp, buf, sizeof(buf));

        if (len < 0)
                return -EINVAL;
        if (len == 0)
                return -ENOENT;

        rv = simple_strtol(buf, &ep, 0);
        if (*ep)
                return -EINVAL;

        *anint = rv;
        return 0;
}

static inline int get_uint(char **bpp, unsigned int *anint)
{
        char buf[50];
        int len = qword_get(bpp, buf, sizeof(buf));

        if (len < 0)
                return -EINVAL;
        if (len == 0)
                return -ENOENT;

        if (kstrtouint(buf, 0, anint))
                return -EINVAL;

        return 0;
}

static inline int get_time(char **bpp, time64_t *time)
{
        char buf[50];
        long long ll;
        int len = qword_get(bpp, buf, sizeof(buf));

        if (len < 0)
                return -EINVAL;
        if (len == 0)
                return -ENOENT;

        if (kstrtoll(buf, 0, &ll))
                return -EINVAL;

        *time = ll;
        return 0;
}

static inline int get_expiry(char **bpp, time64_t *rvp)
{
        int error;
        struct timespec64 boot;

        error = get_time(bpp, rvp);
        if (error)
                return error;

        getboottime64(&boot);
        (*rvp) -= boot.tv_sec;
        return 0;
}

#endif /*  _LINUX_SUNRPC_CACHE_H_ */