Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

[linux-stable.git] / net / sunrpc / cache.c

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

#include <linux/types.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/kmod.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/ctype.h>
#include <linux/string_helpers.h>
#include <linux/uaccess.h>
#include <linux/poll.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/net.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
#include <linux/pagemap.h>
#include <asm/ioctls.h>
#include <linux/sunrpc/types.h>
#include <linux/sunrpc/cache.h>
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include <trace/events/sunrpc.h>

#include "netns.h"
#include "fail.h"

#define  RPCDBG_FACILITY RPCDBG_CACHE

static bool cache_defer_req(struct cache_req *req, struct cache_head *item);
static void cache_revisit_request(struct cache_head *item);

static void cache_init(struct cache_head *h, struct cache_detail *detail)
{
        time64_t now = seconds_since_boot();
        INIT_HLIST_NODE(&h->cache_list);
        h->flags = 0;
        kref_init(&h->ref);
        h->expiry_time = now + CACHE_NEW_EXPIRY;
        if (now <= detail->flush_time)
                /* ensure it isn't already expired */
                now = detail->flush_time + 1;
        h->last_refresh = now;
}

static void cache_fresh_unlocked(struct cache_head *head,
                                struct cache_detail *detail);

static struct cache_head *sunrpc_cache_find_rcu(struct cache_detail *detail,
                                                struct cache_head *key,
                                                int hash)
{
        struct hlist_head *head = &detail->hash_table[hash];
        struct cache_head *tmp;

        rcu_read_lock();
        hlist_for_each_entry_rcu(tmp, head, cache_list) {
                if (!detail->match(tmp, key))
                        continue;
                if (test_bit(CACHE_VALID, &tmp->flags) &&
                    cache_is_expired(detail, tmp))
                        continue;
                tmp = cache_get_rcu(tmp);
                rcu_read_unlock();
                return tmp;
        }
        rcu_read_unlock();
        return NULL;
}

static void sunrpc_begin_cache_remove_entry(struct cache_head *ch,
                                            struct cache_detail *cd)
{
        /* Must be called under cd->hash_lock */
        hlist_del_init_rcu(&ch->cache_list);
        set_bit(CACHE_CLEANED, &ch->flags);
        cd->entries --;
}

static void sunrpc_end_cache_remove_entry(struct cache_head *ch,
                                          struct cache_detail *cd)
{
        cache_fresh_unlocked(ch, cd);
        cache_put(ch, cd);
}

static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
                                                 struct cache_head *key,
                                                 int hash)
{
        struct cache_head *new, *tmp, *freeme = NULL;
        struct hlist_head *head = &detail->hash_table[hash];

        new = detail->alloc();
        if (!new)
                return NULL;
        /* must fully initialise 'new', else
         * we might get lose if we need to
         * cache_put it soon.
         */
        cache_init(new, detail);
        detail->init(new, key);

        spin_lock(&detail->hash_lock);

        /* check if entry appeared while we slept */
        hlist_for_each_entry_rcu(tmp, head, cache_list,
                                 lockdep_is_held(&detail->hash_lock)) {
                if (!detail->match(tmp, key))
                        continue;
                if (test_bit(CACHE_VALID, &tmp->flags) &&
                    cache_is_expired(detail, tmp)) {
                        sunrpc_begin_cache_remove_entry(tmp, detail);
                        trace_cache_entry_expired(detail, tmp);
                        freeme = tmp;
                        break;
                }
                cache_get(tmp);
                spin_unlock(&detail->hash_lock);
                cache_put(new, detail);
                return tmp;
        }

        hlist_add_head_rcu(&new->cache_list, head);
        detail->entries++;
        cache_get(new);
        spin_unlock(&detail->hash_lock);

        if (freeme)
                sunrpc_end_cache_remove_entry(freeme, detail);
        return new;
}

struct cache_head *sunrpc_cache_lookup_rcu(struct cache_detail *detail,
                                           struct cache_head *key, int hash)
{
        struct cache_head *ret;

        ret = sunrpc_cache_find_rcu(detail, key, hash);
        if (ret)
                return ret;
        /* Didn't find anything, insert an empty entry */
        return sunrpc_cache_add_entry(detail, key, hash);
}
EXPORT_SYMBOL_GPL(sunrpc_cache_lookup_rcu);

static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch);

static void cache_fresh_locked(struct cache_head *head, time64_t expiry,
                               struct cache_detail *detail)
{
        time64_t now = seconds_since_boot();
        if (now <= detail->flush_time)
                /* ensure it isn't immediately treated as expired */
                now = detail->flush_time + 1;
        head->expiry_time = expiry;
        head->last_refresh = now;
        smp_wmb(); /* paired with smp_rmb() in cache_is_valid() */
        set_bit(CACHE_VALID, &head->flags);
}

static void cache_fresh_unlocked(struct cache_head *head,
                                 struct cache_detail *detail)
{
        if (test_and_clear_bit(CACHE_PENDING, &head->flags)) {
                cache_revisit_request(head);
                cache_dequeue(detail, head);
        }
}

static void cache_make_negative(struct cache_detail *detail,
                                struct cache_head *h)
{
        set_bit(CACHE_NEGATIVE, &h->flags);
        trace_cache_entry_make_negative(detail, h);
}

static void cache_entry_update(struct cache_detail *detail,
                               struct cache_head *h,
                               struct cache_head *new)
{
        if (!test_bit(CACHE_NEGATIVE, &new->flags)) {
                detail->update(h, new);
                trace_cache_entry_update(detail, h);
        } else {
                cache_make_negative(detail, h);
        }
}

struct cache_head *sunrpc_cache_update(struct cache_detail *detail,
                                       struct cache_head *new, struct cache_head *old, int hash)
{
        /* The 'old' entry is to be replaced by 'new'.
         * If 'old' is not VALID, we update it directly,
         * otherwise we need to replace it
         */
        struct cache_head *tmp;

        if (!test_bit(CACHE_VALID, &old->flags)) {
                spin_lock(&detail->hash_lock);
                if (!test_bit(CACHE_VALID, &old->flags)) {
                        cache_entry_update(detail, old, new);
                        cache_fresh_locked(old, new->expiry_time, detail);
                        spin_unlock(&detail->hash_lock);
                        cache_fresh_unlocked(old, detail);
                        return old;
                }
                spin_unlock(&detail->hash_lock);
        }
        /* We need to insert a new entry */
        tmp = detail->alloc();
        if (!tmp) {
                cache_put(old, detail);
                return NULL;
        }
        cache_init(tmp, detail);
        detail->init(tmp, old);

        spin_lock(&detail->hash_lock);
        cache_entry_update(detail, tmp, new);
        hlist_add_head(&tmp->cache_list, &detail->hash_table[hash]);
        detail->entries++;
        cache_get(tmp);
        cache_fresh_locked(tmp, new->expiry_time, detail);
        cache_fresh_locked(old, 0, detail);
        spin_unlock(&detail->hash_lock);
        cache_fresh_unlocked(tmp, detail);
        cache_fresh_unlocked(old, detail);
        cache_put(old, detail);
        return tmp;
}
EXPORT_SYMBOL_GPL(sunrpc_cache_update);

static inline int cache_is_valid(struct cache_head *h)
{
        if (!test_bit(CACHE_VALID, &h->flags))
                return -EAGAIN;
        else {
                /* entry is valid */
                if (test_bit(CACHE_NEGATIVE, &h->flags))
                        return -ENOENT;
                else {
                        /*
                         * In combination with write barrier in
                         * sunrpc_cache_update, ensures that anyone
                         * using the cache entry after this sees the
                         * updated contents:
                         */
                        smp_rmb();
                        return 0;
                }
        }
}

static int try_to_negate_entry(struct cache_detail *detail, struct cache_head *h)
{
        int rv;

        spin_lock(&detail->hash_lock);
        rv = cache_is_valid(h);
        if (rv == -EAGAIN) {
                cache_make_negative(detail, h);
                cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY,
                                   detail);
                rv = -ENOENT;
        }
        spin_unlock(&detail->hash_lock);
        cache_fresh_unlocked(h, detail);
        return rv;
}

/*
 * This is the generic cache management routine for all
 * the authentication caches.
 * It checks the currency of a cache item and will (later)
 * initiate an upcall to fill it if needed.
 *
 *
 * Returns 0 if the cache_head can be used, or cache_puts it and returns
 * -EAGAIN if upcall is pending and request has been queued
 * -ETIMEDOUT if upcall failed or request could not be queue or
 *           upcall completed but item is still invalid (implying that
 *           the cache item has been replaced with a newer one).
 * -ENOENT if cache entry was negative
 */
int cache_check(struct cache_detail *detail,
                    struct cache_head *h, struct cache_req *rqstp)
{
        int rv;
        time64_t refresh_age, age;

        /* First decide return status as best we can */
        rv = cache_is_valid(h);

        /* now see if we want to start an upcall */
        refresh_age = (h->expiry_time - h->last_refresh);
        age = seconds_since_boot() - h->last_refresh;

        if (rqstp == NULL) {
                if (rv == -EAGAIN)
                        rv = -ENOENT;
        } else if (rv == -EAGAIN ||
                   (h->expiry_time != 0 && age > refresh_age/2)) {
                dprintk("RPC:       Want update, refage=%lld, age=%lld\n",
                                refresh_age, age);
                switch (detail->cache_upcall(detail, h)) {
                case -EINVAL:
                        rv = try_to_negate_entry(detail, h);
                        break;
                case -EAGAIN:
                        cache_fresh_unlocked(h, detail);
                        break;
                }
        }

        if (rv == -EAGAIN) {
                if (!cache_defer_req(rqstp, h)) {
                        /*
                         * Request was not deferred; handle it as best
                         * we can ourselves:
                         */
                        rv = cache_is_valid(h);
                        if (rv == -EAGAIN)
                                rv = -ETIMEDOUT;
                }
        }
        if (rv)
                cache_put(h, detail);
        return rv;
}
EXPORT_SYMBOL_GPL(cache_check);

/*
 * caches need to be periodically cleaned.
 * For this we maintain a list of cache_detail and
 * a current pointer into that list and into the table
 * for that entry.
 *
 * Each time cache_clean is called it finds the next non-empty entry
 * in the current table and walks the list in that entry
 * looking for entries that can be removed.
 *
 * An entry gets removed if:
 * - The expiry is before current time
 * - The last_refresh time is before the flush_time for that cache
 *
 * later we might drop old entries with non-NEVER expiry if that table
 * is getting 'full' for some definition of 'full'
 *
 * The question of "how often to scan a table" is an interesting one
 * and is answered in part by the use of the "nextcheck" field in the
 * cache_detail.
 * When a scan of a table begins, the nextcheck field is set to a time
 * that is well into the future.
 * While scanning, if an expiry time is found that is earlier than the
 * current nextcheck time, nextcheck is set to that expiry time.
 * If the flush_time is ever set to a time earlier than the nextcheck
 * time, the nextcheck time is then set to that flush_time.
 *
 * A table is then only scanned if the current time is at least
 * the nextcheck time.
 *
 */

static LIST_HEAD(cache_list);
static DEFINE_SPINLOCK(cache_list_lock);
static struct cache_detail *current_detail;
static int current_index;

static void do_cache_clean(struct work_struct *work);
static struct delayed_work cache_cleaner;

void sunrpc_init_cache_detail(struct cache_detail *cd)
{
        spin_lock_init(&cd->hash_lock);
        INIT_LIST_HEAD(&cd->queue);
        spin_lock(&cache_list_lock);
        cd->nextcheck = 0;
        cd->entries = 0;
        atomic_set(&cd->writers, 0);
        cd->last_close = 0;
        cd->last_warn = -1;
        list_add(&cd->others, &cache_list);
        spin_unlock(&cache_list_lock);

        /* start the cleaning process */
        queue_delayed_work(system_power_efficient_wq, &cache_cleaner, 0);
}
EXPORT_SYMBOL_GPL(sunrpc_init_cache_detail);

void sunrpc_destroy_cache_detail(struct cache_detail *cd)
{
        cache_purge(cd);
        spin_lock(&cache_list_lock);
        spin_lock(&cd->hash_lock);
        if (current_detail == cd)
                current_detail = NULL;
        list_del_init(&cd->others);
        spin_unlock(&cd->hash_lock);
        spin_unlock(&cache_list_lock);
        if (list_empty(&cache_list)) {
                /* module must be being unloaded so its safe to kill the worker */
                cancel_delayed_work_sync(&cache_cleaner);
        }
}
EXPORT_SYMBOL_GPL(sunrpc_destroy_cache_detail);

/* clean cache tries to find something to clean
 * and cleans it.
 * It returns 1 if it cleaned something,
 *            0 if it didn't find anything this time
 *           -1 if it fell off the end of the list.
 */
static int cache_clean(void)
{
        int rv = 0;
        struct list_head *next;

        spin_lock(&cache_list_lock);

        /* find a suitable table if we don't already have one */
        while (current_detail == NULL ||
            current_index >= current_detail->hash_size) {
                if (current_detail)
                        next = current_detail->others.next;
                else
                        next = cache_list.next;
                if (next == &cache_list) {
                        current_detail = NULL;
                        spin_unlock(&cache_list_lock);
                        return -1;
                }
                current_detail = list_entry(next, struct cache_detail, others);
                if (current_detail->nextcheck > seconds_since_boot())
                        current_index = current_detail->hash_size;
                else {
                        current_index = 0;
                        current_detail->nextcheck = seconds_since_boot()+30*60;
                }
        }

        /* find a non-empty bucket in the table */
        while (current_detail &&
               current_index < current_detail->hash_size &&
               hlist_empty(&current_detail->hash_table[current_index]))
                current_index++;

        /* find a cleanable entry in the bucket and clean it, or set to next bucket */

        if (current_detail && current_index < current_detail->hash_size) {
                struct cache_head *ch = NULL;
                struct cache_detail *d;
                struct hlist_head *head;
                struct hlist_node *tmp;

                spin_lock(&current_detail->hash_lock);

                /* Ok, now to clean this strand */

                head = &current_detail->hash_table[current_index];
                hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
                        if (current_detail->nextcheck > ch->expiry_time)
                                current_detail->nextcheck = ch->expiry_time+1;
                        if (!cache_is_expired(current_detail, ch))
                                continue;

                        sunrpc_begin_cache_remove_entry(ch, current_detail);
                        trace_cache_entry_expired(current_detail, ch);
                        rv = 1;
                        break;
                }

                spin_unlock(&current_detail->hash_lock);
                d = current_detail;
                if (!ch)
                        current_index ++;
                spin_unlock(&cache_list_lock);
                if (ch)
                        sunrpc_end_cache_remove_entry(ch, d);
        } else
                spin_unlock(&cache_list_lock);

        return rv;
}

/*
 * We want to regularly clean the cache, so we need to schedule some work ...
 */
static void do_cache_clean(struct work_struct *work)
{
        int delay;

        if (list_empty(&cache_list))
                return;

        if (cache_clean() == -1)
                delay = round_jiffies_relative(30*HZ);
        else
                delay = 5;

        queue_delayed_work(system_power_efficient_wq, &cache_cleaner, delay);
}


/*
 * Clean all caches promptly.  This just calls cache_clean
 * repeatedly until we are sure that every cache has had a chance to
 * be fully cleaned
 */
void cache_flush(void)
{
        while (cache_clean() != -1)
                cond_resched();
        while (cache_clean() != -1)
                cond_resched();
}
EXPORT_SYMBOL_GPL(cache_flush);

void cache_purge(struct cache_detail *detail)
{
        struct cache_head *ch = NULL;
        struct hlist_head *head = NULL;
        int i = 0;

        spin_lock(&detail->hash_lock);
        if (!detail->entries) {
                spin_unlock(&detail->hash_lock);
                return;
        }

        dprintk("RPC: %d entries in %s cache\n", detail->entries, detail->name);
        for (i = 0; i < detail->hash_size; i++) {
                head = &detail->hash_table[i];
                while (!hlist_empty(head)) {
                        ch = hlist_entry(head->first, struct cache_head,
                                         cache_list);
                        sunrpc_begin_cache_remove_entry(ch, detail);
                        spin_unlock(&detail->hash_lock);
                        sunrpc_end_cache_remove_entry(ch, detail);
                        spin_lock(&detail->hash_lock);
                }
        }
        spin_unlock(&detail->hash_lock);
}
EXPORT_SYMBOL_GPL(cache_purge);


/*
 * Deferral and Revisiting of Requests.
 *
 * If a cache lookup finds a pending entry, we
 * need to defer the request and revisit it later.
 * All deferred requests are stored in a hash table,
 * indexed by "struct cache_head *".
 * As it may be wasteful to store a whole request
 * structure, we allow the request to provide a
 * deferred form, which must contain a
 * 'struct cache_deferred_req'
 * This cache_deferred_req contains a method to allow
 * it to be revisited when cache info is available
 */

#define DFR_HASHSIZE    (PAGE_SIZE/sizeof(struct list_head))
#define DFR_HASH(item)  ((((long)item)>>4 ^ (((long)item)>>13)) % DFR_HASHSIZE)

#define DFR_MAX 300     /* ??? */

static DEFINE_SPINLOCK(cache_defer_lock);
static LIST_HEAD(cache_defer_list);
static struct hlist_head cache_defer_hash[DFR_HASHSIZE];
static int cache_defer_cnt;

static void __unhash_deferred_req(struct cache_deferred_req *dreq)
{
        hlist_del_init(&dreq->hash);
        if (!list_empty(&dreq->recent)) {
                list_del_init(&dreq->recent);
                cache_defer_cnt--;
        }
}

static void __hash_deferred_req(struct cache_deferred_req *dreq, struct cache_head *item)
{
        int hash = DFR_HASH(item);

        INIT_LIST_HEAD(&dreq->recent);
        hlist_add_head(&dreq->hash, &cache_defer_hash[hash]);
}

static void setup_deferral(struct cache_deferred_req *dreq,
                           struct cache_head *item,
                           int count_me)
{

        dreq->item = item;

        spin_lock(&cache_defer_lock);

        __hash_deferred_req(dreq, item);

        if (count_me) {
                cache_defer_cnt++;
                list_add(&dreq->recent, &cache_defer_list);
        }

        spin_unlock(&cache_defer_lock);

}

struct thread_deferred_req {
        struct cache_deferred_req handle;
        struct completion completion;
};

static void cache_restart_thread(struct cache_deferred_req *dreq, int too_many)
{
        struct thread_deferred_req *dr =
                container_of(dreq, struct thread_deferred_req, handle);
        complete(&dr->completion);
}

static void cache_wait_req(struct cache_req *req, struct cache_head *item)
{
        struct thread_deferred_req sleeper;
        struct cache_deferred_req *dreq = &sleeper.handle;

        sleeper.completion = COMPLETION_INITIALIZER_ONSTACK(sleeper.completion);
        dreq->revisit = cache_restart_thread;

        setup_deferral(dreq, item, 0);

        if (!test_bit(CACHE_PENDING, &item->flags) ||
            wait_for_completion_interruptible_timeout(
                    &sleeper.completion, req->thread_wait) <= 0) {
                /* The completion wasn't completed, so we need
                 * to clean up
                 */
                spin_lock(&cache_defer_lock);
                if (!hlist_unhashed(&sleeper.handle.hash)) {
                        __unhash_deferred_req(&sleeper.handle);
                        spin_unlock(&cache_defer_lock);
                } else {
                        /* cache_revisit_request already removed
                         * this from the hash table, but hasn't
                         * called ->revisit yet.  It will very soon
                         * and we need to wait for it.
                         */
                        spin_unlock(&cache_defer_lock);
                        wait_for_completion(&sleeper.completion);
                }
        }
}

static void cache_limit_defers(void)
{
        /* Make sure we haven't exceed the limit of allowed deferred
         * requests.
         */
        struct cache_deferred_req *discard = NULL;

        if (cache_defer_cnt <= DFR_MAX)
                return;

        spin_lock(&cache_defer_lock);

        /* Consider removing either the first or the last */
        if (cache_defer_cnt > DFR_MAX) {
                if (get_random_u32_below(2))
                        discard = list_entry(cache_defer_list.next,
                                             struct cache_deferred_req, recent);
                else
                        discard = list_entry(cache_defer_list.prev,
                                             struct cache_deferred_req, recent);
                __unhash_deferred_req(discard);
        }
        spin_unlock(&cache_defer_lock);
        if (discard)
                discard->revisit(discard, 1);
}

#if IS_ENABLED(CONFIG_FAIL_SUNRPC)
static inline bool cache_defer_immediately(void)
{
        return !fail_sunrpc.ignore_cache_wait &&
                should_fail(&fail_sunrpc.attr, 1);
}
#else
static inline bool cache_defer_immediately(void)
{
        return false;
}
#endif

/* Return true if and only if a deferred request is queued. */
static bool cache_defer_req(struct cache_req *req, struct cache_head *item)
{
        struct cache_deferred_req *dreq;

        if (!cache_defer_immediately()) {
                cache_wait_req(req, item);
                if (!test_bit(CACHE_PENDING, &item->flags))
                        return false;
        }

        dreq = req->defer(req);
        if (dreq == NULL)
                return false;
        setup_deferral(dreq, item, 1);
        if (!test_bit(CACHE_PENDING, &item->flags))
                /* Bit could have been cleared before we managed to
                 * set up the deferral, so need to revisit just in case
                 */
                cache_revisit_request(item);

        cache_limit_defers();
        return true;
}

static void cache_revisit_request(struct cache_head *item)
{
        struct cache_deferred_req *dreq;
        struct hlist_node *tmp;
        int hash = DFR_HASH(item);
        LIST_HEAD(pending);

        spin_lock(&cache_defer_lock);

        hlist_for_each_entry_safe(dreq, tmp, &cache_defer_hash[hash], hash)
                if (dreq->item == item) {
                        __unhash_deferred_req(dreq);
                        list_add(&dreq->recent, &pending);
                }

        spin_unlock(&cache_defer_lock);

        while (!list_empty(&pending)) {
                dreq = list_entry(pending.next, struct cache_deferred_req, recent);
                list_del_init(&dreq->recent);
                dreq->revisit(dreq, 0);
        }
}

void cache_clean_deferred(void *owner)
{
        struct cache_deferred_req *dreq, *tmp;
        LIST_HEAD(pending);

        spin_lock(&cache_defer_lock);

        list_for_each_entry_safe(dreq, tmp, &cache_defer_list, recent) {
                if (dreq->owner == owner) {
                        __unhash_deferred_req(dreq);
                        list_add(&dreq->recent, &pending);
                }
        }
        spin_unlock(&cache_defer_lock);

        while (!list_empty(&pending)) {
                dreq = list_entry(pending.next, struct cache_deferred_req, recent);
                list_del_init(&dreq->recent);
                dreq->revisit(dreq, 1);
        }
}

/*
 * communicate with user-space
 *
 * We have a magic /proc file - /proc/net/rpc/<cachename>/channel.
 * On read, you get a full request, or block.
 * On write, an update request is processed.
 * Poll works if anything to read, and always allows write.
 *
 * Implemented by linked list of requests.  Each open file has
 * a ->private that also exists in this list.  New requests are added
 * to the end and may wakeup and preceding readers.
 * New readers are added to the head.  If, on read, an item is found with
 * CACHE_UPCALLING clear, we free it from the list.
 *
 */

static DEFINE_SPINLOCK(queue_lock);

struct cache_queue {
        struct list_head        list;
        int                     reader; /* if 0, then request */
};
struct cache_request {
        struct cache_queue      q;
        struct cache_head       *item;
        char                    * buf;
        int                     len;
        int                     readers;
};
struct cache_reader {
        struct cache_queue      q;
        int                     offset; /* if non-0, we have a refcnt on next request */
};

static int cache_request(struct cache_detail *detail,
                               struct cache_request *crq)
{
        char *bp = crq->buf;
        int len = PAGE_SIZE;

        detail->cache_request(detail, crq->item, &bp, &len);
        if (len < 0)
                return -E2BIG;
        return PAGE_SIZE - len;
}

static ssize_t cache_read(struct file *filp, char __user *buf, size_t count,
                          loff_t *ppos, struct cache_detail *cd)
{
        struct cache_reader *rp = filp->private_data;
        struct cache_request *rq;
        struct inode *inode = file_inode(filp);
        int err;

        if (count == 0)
                return 0;

        inode_lock(inode); /* protect against multiple concurrent
                              * readers on this file */
 again:
        spin_lock(&queue_lock);
        /* need to find next request */
        while (rp->q.list.next != &cd->queue &&
               list_entry(rp->q.list.next, struct cache_queue, list)
               ->reader) {
                struct list_head *next = rp->q.list.next;
                list_move(&rp->q.list, next);
        }
        if (rp->q.list.next == &cd->queue) {
                spin_unlock(&queue_lock);
                inode_unlock(inode);
                WARN_ON_ONCE(rp->offset);
                return 0;
        }
        rq = container_of(rp->q.list.next, struct cache_request, q.list);
        WARN_ON_ONCE(rq->q.reader);
        if (rp->offset == 0)
                rq->readers++;
        spin_unlock(&queue_lock);

        if (rq->len == 0) {
                err = cache_request(cd, rq);
                if (err < 0)
                        goto out;
                rq->len = err;
        }

        if (rp->offset == 0 && !test_bit(CACHE_PENDING, &rq->item->flags)) {
                err = -EAGAIN;
                spin_lock(&queue_lock);
                list_move(&rp->q.list, &rq->q.list);
                spin_unlock(&queue_lock);
        } else {
                if (rp->offset + count > rq->len)
                        count = rq->len - rp->offset;
                err = -EFAULT;
                if (copy_to_user(buf, rq->buf + rp->offset, count))
                        goto out;
                rp->offset += count;
                if (rp->offset >= rq->len) {
                        rp->offset = 0;
                        spin_lock(&queue_lock);
                        list_move(&rp->q.list, &rq->q.list);
                        spin_unlock(&queue_lock);
                }
                err = 0;
        }
 out:
        if (rp->offset == 0) {
                /* need to release rq */
                spin_lock(&queue_lock);
                rq->readers--;
                if (rq->readers == 0 &&
                    !test_bit(CACHE_PENDING, &rq->item->flags)) {
                        list_del(&rq->q.list);
                        spin_unlock(&queue_lock);
                        cache_put(rq->item, cd);
                        kfree(rq->buf);
                        kfree(rq);
                } else
                        spin_unlock(&queue_lock);
        }
        if (err == -EAGAIN)
                goto again;
        inode_unlock(inode);
        return err ? err :  count;
}

static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
                                 size_t count, struct cache_detail *cd)
{
        ssize_t ret;

        if (count == 0)
                return -EINVAL;
        if (copy_from_user(kaddr, buf, count))
                return -EFAULT;
        kaddr[count] = '\0';
        ret = cd->cache_parse(cd, kaddr, count);
        if (!ret)
                ret = count;
        return ret;
}

static ssize_t cache_downcall(struct address_space *mapping,
                              const char __user *buf,
                              size_t count, struct cache_detail *cd)
{
        char *write_buf;
        ssize_t ret = -ENOMEM;

        if (count >= 32768) { /* 32k is max userland buffer, lets check anyway */
                ret = -EINVAL;
                goto out;
        }

        write_buf = kvmalloc(count + 1, GFP_KERNEL);
        if (!write_buf)
                goto out;

        ret = cache_do_downcall(write_buf, buf, count, cd);
        kvfree(write_buf);
out:
        return ret;
}

static ssize_t cache_write(struct file *filp, const char __user *buf,
                           size_t count, loff_t *ppos,
                           struct cache_detail *cd)
{
        struct address_space *mapping = filp->f_mapping;
        struct inode *inode = file_inode(filp);
        ssize_t ret = -EINVAL;

        if (!cd->cache_parse)
                goto out;

        inode_lock(inode);
        ret = cache_downcall(mapping, buf, count, cd);
        inode_unlock(inode);
out:
        return ret;
}

static DECLARE_WAIT_QUEUE_HEAD(queue_wait);

static __poll_t cache_poll(struct file *filp, poll_table *wait,
                               struct cache_detail *cd)
{
        __poll_t mask;
        struct cache_reader *rp = filp->private_data;
        struct cache_queue *cq;

        poll_wait(filp, &queue_wait, wait);

        /* alway allow write */
        mask = EPOLLOUT | EPOLLWRNORM;

        if (!rp)
                return mask;

        spin_lock(&queue_lock);

        for (cq= &rp->q; &cq->list != &cd->queue;
             cq = list_entry(cq->list.next, struct cache_queue, list))
                if (!cq->reader) {
                        mask |= EPOLLIN | EPOLLRDNORM;
                        break;
                }
        spin_unlock(&queue_lock);
        return mask;
}

static int cache_ioctl(struct inode *ino, struct file *filp,
                       unsigned int cmd, unsigned long arg,
                       struct cache_detail *cd)
{
        int len = 0;
        struct cache_reader *rp = filp->private_data;
        struct cache_queue *cq;

        if (cmd != FIONREAD || !rp)
                return -EINVAL;

        spin_lock(&queue_lock);

        /* only find the length remaining in current request,
         * or the length of the next request
         */
        for (cq= &rp->q; &cq->list != &cd->queue;
             cq = list_entry(cq->list.next, struct cache_queue, list))
                if (!cq->reader) {
                        struct cache_request *cr =
                                container_of(cq, struct cache_request, q);
                        len = cr->len - rp->offset;
                        break;
                }
        spin_unlock(&queue_lock);

        return put_user(len, (int __user *)arg);
}

static int cache_open(struct inode *inode, struct file *filp,
                      struct cache_detail *cd)
{
        struct cache_reader *rp = NULL;

        if (!cd || !try_module_get(cd->owner))
                return -EACCES;
        nonseekable_open(inode, filp);
        if (filp->f_mode & FMODE_READ) {
                rp = kmalloc(sizeof(*rp), GFP_KERNEL);
                if (!rp) {
                        module_put(cd->owner);
                        return -ENOMEM;
                }
                rp->offset = 0;
                rp->q.reader = 1;

                spin_lock(&queue_lock);
                list_add(&rp->q.list, &cd->queue);
                spin_unlock(&queue_lock);
        }
        if (filp->f_mode & FMODE_WRITE)
                atomic_inc(&cd->writers);
        filp->private_data = rp;
        return 0;
}

static int cache_release(struct inode *inode, struct file *filp,
                         struct cache_detail *cd)
{
        struct cache_reader *rp = filp->private_data;

        if (rp) {
                spin_lock(&queue_lock);
                if (rp->offset) {
                        struct cache_queue *cq;
                        for (cq= &rp->q; &cq->list != &cd->queue;
                             cq = list_entry(cq->list.next, struct cache_queue, list))
                                if (!cq->reader) {
                                        container_of(cq, struct cache_request, q)
                                                ->readers--;
                                        break;
                                }
                        rp->offset = 0;
                }
                list_del(&rp->q.list);
                spin_unlock(&queue_lock);

                filp->private_data = NULL;
                kfree(rp);

        }
        if (filp->f_mode & FMODE_WRITE) {
                atomic_dec(&cd->writers);
                cd->last_close = seconds_since_boot();
        }
        module_put(cd->owner);
        return 0;
}



static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch)
{
        struct cache_queue *cq, *tmp;
        struct cache_request *cr;
        LIST_HEAD(dequeued);

        spin_lock(&queue_lock);
        list_for_each_entry_safe(cq, tmp, &detail->queue, list)
                if (!cq->reader) {
                        cr = container_of(cq, struct cache_request, q);
                        if (cr->item != ch)
                                continue;
                        if (test_bit(CACHE_PENDING, &ch->flags))
                                /* Lost a race and it is pending again */
                                break;
                        if (cr->readers != 0)
                                continue;
                        list_move(&cr->q.list, &dequeued);
                }
        spin_unlock(&queue_lock);
        while (!list_empty(&dequeued)) {
                cr = list_entry(dequeued.next, struct cache_request, q.list);
                list_del(&cr->q.list);
                cache_put(cr->item, detail);
                kfree(cr->buf);
                kfree(cr);
        }
}

/*
 * Support routines for text-based upcalls.
 * Fields are separated by spaces.
 * Fields are either mangled to quote space tab newline slosh with slosh
 * or a hexified with a leading \x
 * Record is terminated with newline.
 *
 */

void qword_add(char **bpp, int *lp, char *str)
{
        char *bp = *bpp;
        int len = *lp;
        int ret;

        if (len < 0) return;

        ret = string_escape_str(str, bp, len, ESCAPE_OCTAL, "\\ \n\t");
        if (ret >= len) {
                bp += len;
                len = -1;
        } else {
                bp += ret;
                len -= ret;
                *bp++ = ' ';
                len--;
        }
        *bpp = bp;
        *lp = len;
}
EXPORT_SYMBOL_GPL(qword_add);

void qword_addhex(char **bpp, int *lp, char *buf, int blen)
{
        char *bp = *bpp;
        int len = *lp;

        if (len < 0) return;

        if (len > 2) {
                *bp++ = '\\';
                *bp++ = 'x';
                len -= 2;
                while (blen && len >= 2) {
                        bp = hex_byte_pack(bp, *buf++);
                        len -= 2;
                        blen--;
                }
        }
        if (blen || len<1) len = -1;
        else {
                *bp++ = ' ';
                len--;
        }
        *bpp = bp;
        *lp = len;
}
EXPORT_SYMBOL_GPL(qword_addhex);

static void warn_no_listener(struct cache_detail *detail)
{
        if (detail->last_warn != detail->last_close) {
                detail->last_warn = detail->last_close;
                if (detail->warn_no_listener)
                        detail->warn_no_listener(detail, detail->last_close != 0);
        }
}

static bool cache_listeners_exist(struct cache_detail *detail)
{
        if (atomic_read(&detail->writers))
                return true;
        if (detail->last_close == 0)
                /* This cache was never opened */
                return false;
        if (detail->last_close < seconds_since_boot() - 30)
                /*
                 * We allow for the possibility that someone might
                 * restart a userspace daemon without restarting the
                 * server; but after 30 seconds, we give up.
                 */
                 return false;
        return true;
}

/*
 * register an upcall request to user-space and queue it up for read() by the
 * upcall daemon.
 *
 * Each request is at most one page long.
 */
static int cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h)
{
        char *buf;
        struct cache_request *crq;
        int ret = 0;

        if (test_bit(CACHE_CLEANED, &h->flags))
                /* Too late to make an upcall */
                return -EAGAIN;

        buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (!buf)
                return -EAGAIN;

        crq = kmalloc(sizeof (*crq), GFP_KERNEL);
        if (!crq) {
                kfree(buf);
                return -EAGAIN;
        }

        crq->q.reader = 0;
        crq->buf = buf;
        crq->len = 0;
        crq->readers = 0;
        spin_lock(&queue_lock);
        if (test_bit(CACHE_PENDING, &h->flags)) {
                crq->item = cache_get(h);
                list_add_tail(&crq->q.list, &detail->queue);
                trace_cache_entry_upcall(detail, h);
        } else
                /* Lost a race, no longer PENDING, so don't enqueue */
                ret = -EAGAIN;
        spin_unlock(&queue_lock);
        wake_up(&queue_wait);
        if (ret == -EAGAIN) {
                kfree(buf);
                kfree(crq);
        }
        return ret;
}

int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h)
{
        if (test_and_set_bit(CACHE_PENDING, &h->flags))
                return 0;
        return cache_pipe_upcall(detail, h);
}
EXPORT_SYMBOL_GPL(sunrpc_cache_pipe_upcall);

int sunrpc_cache_pipe_upcall_timeout(struct cache_detail *detail,
                                     struct cache_head *h)
{
        if (!cache_listeners_exist(detail)) {
                warn_no_listener(detail);
                trace_cache_entry_no_listener(detail, h);
                return -EINVAL;
        }
        return sunrpc_cache_pipe_upcall(detail, h);
}
EXPORT_SYMBOL_GPL(sunrpc_cache_pipe_upcall_timeout);

/*
 * parse a message from user-space and pass it
 * to an appropriate cache
 * Messages are, like requests, separated into fields by
 * spaces and dequotes as \xHEXSTRING or embedded \nnn octal
 *
 * Message is
 *   reply cachename expiry key ... content....
 *
 * key and content are both parsed by cache
 */

int qword_get(char **bpp, char *dest, int bufsize)
{
        /* return bytes copied, or -1 on error */
        char *bp = *bpp;
        int len = 0;

        while (*bp == ' ') bp++;

        if (bp[0] == '\\' && bp[1] == 'x') {
                /* HEX STRING */
                bp += 2;
                while (len < bufsize - 1) {
                        int h, l;

                        h = hex_to_bin(bp[0]);
                        if (h < 0)
                                break;

                        l = hex_to_bin(bp[1]);
                        if (l < 0)
                                break;

                        *dest++ = (h << 4) | l;
                        bp += 2;
                        len++;
                }
        } else {
                /* text with \nnn octal quoting */
                while (*bp != ' ' && *bp != '\n' && *bp && len < bufsize-1) {
                        if (*bp == '\\' &&
                            isodigit(bp[1]) && (bp[1] <= '3') &&
                            isodigit(bp[2]) &&
                            isodigit(bp[3])) {
                                int byte = (*++bp -'0');
                                bp++;
                                byte = (byte << 3) | (*bp++ - '0');
                                byte = (byte << 3) | (*bp++ - '0');
                                *dest++ = byte;
                                len++;
                        } else {
                                *dest++ = *bp++;
                                len++;
                        }
                }
        }

        if (*bp != ' ' && *bp != '\n' && *bp != '\0')
                return -1;
        while (*bp == ' ') bp++;
        *bpp = bp;
        *dest = '\0';
        return len;
}
EXPORT_SYMBOL_GPL(qword_get);


/*
 * support /proc/net/rpc/$CACHENAME/content
 * as a seqfile.
 * We call ->cache_show passing NULL for the item to
 * get a header, then pass each real item in the cache
 */

static void *__cache_seq_start(struct seq_file *m, loff_t *pos)
{
        loff_t n = *pos;
        unsigned int hash, entry;
        struct cache_head *ch;
        struct cache_detail *cd = m->private;

        if (!n--)
                return SEQ_START_TOKEN;
        hash = n >> 32;
        entry = n & ((1LL<<32) - 1);

        hlist_for_each_entry_rcu(ch, &cd->hash_table[hash], cache_list)
                if (!entry--)
                        return ch;
        n &= ~((1LL<<32) - 1);
        do {
                hash++;
                n += 1LL<<32;
        } while(hash < cd->hash_size &&
                hlist_empty(&cd->hash_table[hash]));
        if (hash >= cd->hash_size)
                return NULL;
        *pos = n+1;
        return hlist_entry_safe(rcu_dereference_raw(
                                hlist_first_rcu(&cd->hash_table[hash])),
                                struct cache_head, cache_list);
}

static void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
{
        struct cache_head *ch = p;
        int hash = (*pos >> 32);
        struct cache_detail *cd = m->private;

        if (p == SEQ_START_TOKEN)
                hash = 0;
        else if (ch->cache_list.next == NULL) {
                hash++;
                *pos += 1LL<<32;
        } else {
                ++*pos;
                return hlist_entry_safe(rcu_dereference_raw(
                                        hlist_next_rcu(&ch->cache_list)),
                                        struct cache_head, cache_list);
        }
        *pos &= ~((1LL<<32) - 1);
        while (hash < cd->hash_size &&
               hlist_empty(&cd->hash_table[hash])) {
                hash++;
                *pos += 1LL<<32;
        }
        if (hash >= cd->hash_size)
                return NULL;
        ++*pos;
        return hlist_entry_safe(rcu_dereference_raw(
                                hlist_first_rcu(&cd->hash_table[hash])),
                                struct cache_head, cache_list);
}

void *cache_seq_start_rcu(struct seq_file *m, loff_t *pos)
        __acquires(RCU)
{
        rcu_read_lock();
        return __cache_seq_start(m, pos);
}
EXPORT_SYMBOL_GPL(cache_seq_start_rcu);

void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos)
{
        return cache_seq_next(file, p, pos);
}
EXPORT_SYMBOL_GPL(cache_seq_next_rcu);

void cache_seq_stop_rcu(struct seq_file *m, void *p)
        __releases(RCU)
{
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(cache_seq_stop_rcu);

static int c_show(struct seq_file *m, void *p)
{
        struct cache_head *cp = p;
        struct cache_detail *cd = m->private;

        if (p == SEQ_START_TOKEN)
                return cd->cache_show(m, cd, NULL);

        ifdebug(CACHE)
                seq_printf(m, "# expiry=%lld refcnt=%d flags=%lx\n",
                           convert_to_wallclock(cp->expiry_time),
                           kref_read(&cp->ref), cp->flags);
        cache_get(cp);
        if (cache_check(cd, cp, NULL))
                /* cache_check does a cache_put on failure */
                seq_puts(m, "# ");
        else {
                if (cache_is_expired(cd, cp))
                        seq_puts(m, "# ");
                cache_put(cp, cd);
        }

        return cd->cache_show(m, cd, cp);
}

static const struct seq_operations cache_content_op = {
        .start  = cache_seq_start_rcu,
        .next   = cache_seq_next_rcu,
        .stop   = cache_seq_stop_rcu,
        .show   = c_show,
};

static int content_open(struct inode *inode, struct file *file,
                        struct cache_detail *cd)
{
        struct seq_file *seq;
        int err;

        if (!cd || !try_module_get(cd->owner))
                return -EACCES;

        err = seq_open(file, &cache_content_op);
        if (err) {
                module_put(cd->owner);
                return err;
        }

        seq = file->private_data;
        seq->private = cd;
        return 0;
}

static int content_release(struct inode *inode, struct file *file,
                struct cache_detail *cd)
{
        int ret = seq_release(inode, file);
        module_put(cd->owner);
        return ret;
}

static int open_flush(struct inode *inode, struct file *file,
                        struct cache_detail *cd)
{
        if (!cd || !try_module_get(cd->owner))
                return -EACCES;
        return nonseekable_open(inode, file);
}

static int release_flush(struct inode *inode, struct file *file,
                        struct cache_detail *cd)
{
        module_put(cd->owner);
        return 0;
}

static ssize_t read_flush(struct file *file, char __user *buf,
                          size_t count, loff_t *ppos,
                          struct cache_detail *cd)
{
        char tbuf[22];
        size_t len;

        len = snprintf(tbuf, sizeof(tbuf), "%llu\n",
                        convert_to_wallclock(cd->flush_time));
        return simple_read_from_buffer(buf, count, ppos, tbuf, len);
}

static ssize_t write_flush(struct file *file, const char __user *buf,
                           size_t count, loff_t *ppos,
                           struct cache_detail *cd)
{
        char tbuf[20];
        char *ep;
        time64_t now;

        if (*ppos || count > sizeof(tbuf)-1)
                return -EINVAL;
        if (copy_from_user(tbuf, buf, count))
                return -EFAULT;
        tbuf[count] = 0;
        simple_strtoul(tbuf, &ep, 0);
        if (*ep && *ep != '\n')
                return -EINVAL;
        /* Note that while we check that 'buf' holds a valid number,
         * we always ignore the value and just flush everything.
         * Making use of the number leads to races.
         */

        now = seconds_since_boot();
        /* Always flush everything, so behave like cache_purge()
         * Do this by advancing flush_time to the current time,
         * or by one second if it has already reached the current time.
         * Newly added cache entries will always have ->last_refresh greater
         * that ->flush_time, so they don't get flushed prematurely.
         */

        if (cd->flush_time >= now)
                now = cd->flush_time + 1;

        cd->flush_time = now;
        cd->nextcheck = now;
        cache_flush();

        if (cd->flush)
                cd->flush();

        *ppos += count;
        return count;
}

static ssize_t cache_read_procfs(struct file *filp, char __user *buf,
                                 size_t count, loff_t *ppos)
{
        struct cache_detail *cd = pde_data(file_inode(filp));

        return cache_read(filp, buf, count, ppos, cd);
}

static ssize_t cache_write_procfs(struct file *filp, const char __user *buf,
                                  size_t count, loff_t *ppos)
{
        struct cache_detail *cd = pde_data(file_inode(filp));

        return cache_write(filp, buf, count, ppos, cd);
}

static __poll_t cache_poll_procfs(struct file *filp, poll_table *wait)
{
        struct cache_detail *cd = pde_data(file_inode(filp));

        return cache_poll(filp, wait, cd);
}

static long cache_ioctl_procfs(struct file *filp,
                               unsigned int cmd, unsigned long arg)
{
        struct inode *inode = file_inode(filp);
        struct cache_detail *cd = pde_data(inode);

        return cache_ioctl(inode, filp, cmd, arg, cd);
}

static int cache_open_procfs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = pde_data(inode);

        return cache_open(inode, filp, cd);
}

static int cache_release_procfs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = pde_data(inode);

        return cache_release(inode, filp, cd);
}

static const struct proc_ops cache_channel_proc_ops = {
        .proc_read      = cache_read_procfs,
        .proc_write     = cache_write_procfs,
        .proc_poll      = cache_poll_procfs,
        .proc_ioctl     = cache_ioctl_procfs, /* for FIONREAD */
        .proc_open      = cache_open_procfs,
        .proc_release   = cache_release_procfs,
};

static int content_open_procfs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = pde_data(inode);

        return content_open(inode, filp, cd);
}

static int content_release_procfs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = pde_data(inode);

        return content_release(inode, filp, cd);
}

static const struct proc_ops content_proc_ops = {
        .proc_open      = content_open_procfs,
        .proc_read      = seq_read,
        .proc_lseek     = seq_lseek,
        .proc_release   = content_release_procfs,
};

static int open_flush_procfs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = pde_data(inode);

        return open_flush(inode, filp, cd);
}

static int release_flush_procfs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = pde_data(inode);

        return release_flush(inode, filp, cd);
}

static ssize_t read_flush_procfs(struct file *filp, char __user *buf,
                            size_t count, loff_t *ppos)
{
        struct cache_detail *cd = pde_data(file_inode(filp));

        return read_flush(filp, buf, count, ppos, cd);
}

static ssize_t write_flush_procfs(struct file *filp,
                                  const char __user *buf,
                                  size_t count, loff_t *ppos)
{
        struct cache_detail *cd = pde_data(file_inode(filp));

        return write_flush(filp, buf, count, ppos, cd);
}

static const struct proc_ops cache_flush_proc_ops = {
        .proc_open      = open_flush_procfs,
        .proc_read      = read_flush_procfs,
        .proc_write     = write_flush_procfs,
        .proc_release   = release_flush_procfs,
};

static void remove_cache_proc_entries(struct cache_detail *cd)
{
        if (cd->procfs) {
                proc_remove(cd->procfs);
                cd->procfs = NULL;
        }
}

#ifdef CONFIG_PROC_FS
static int create_cache_proc_entries(struct cache_detail *cd, struct net *net)
{
        struct proc_dir_entry *p;
        struct sunrpc_net *sn;

        sn = net_generic(net, sunrpc_net_id);
        cd->procfs = proc_mkdir(cd->name, sn->proc_net_rpc);
        if (cd->procfs == NULL)
                goto out_nomem;

        p = proc_create_data("flush", S_IFREG | 0600,
                             cd->procfs, &cache_flush_proc_ops, cd);
        if (p == NULL)
                goto out_nomem;

        if (cd->cache_request || cd->cache_parse) {
                p = proc_create_data("channel", S_IFREG | 0600, cd->procfs,
                                     &cache_channel_proc_ops, cd);
                if (p == NULL)
                        goto out_nomem;
        }
        if (cd->cache_show) {
                p = proc_create_data("content", S_IFREG | 0400, cd->procfs,
                                     &content_proc_ops, cd);
                if (p == NULL)
                        goto out_nomem;
        }
        return 0;
out_nomem:
        remove_cache_proc_entries(cd);
        return -ENOMEM;
}
#else /* CONFIG_PROC_FS */
static int create_cache_proc_entries(struct cache_detail *cd, struct net *net)
{
        return 0;
}
#endif

void __init cache_initialize(void)
{
        INIT_DEFERRABLE_WORK(&cache_cleaner, do_cache_clean);
}

int cache_register_net(struct cache_detail *cd, struct net *net)
{
        int ret;

        sunrpc_init_cache_detail(cd);
        ret = create_cache_proc_entries(cd, net);
        if (ret)
                sunrpc_destroy_cache_detail(cd);
        return ret;
}
EXPORT_SYMBOL_GPL(cache_register_net);

void cache_unregister_net(struct cache_detail *cd, struct net *net)
{
        remove_cache_proc_entries(cd);
        sunrpc_destroy_cache_detail(cd);
}
EXPORT_SYMBOL_GPL(cache_unregister_net);

struct cache_detail *cache_create_net(const struct cache_detail *tmpl, struct net *net)
{
        struct cache_detail *cd;
        int i;

        cd = kmemdup(tmpl, sizeof(struct cache_detail), GFP_KERNEL);
        if (cd == NULL)
                return ERR_PTR(-ENOMEM);

        cd->hash_table = kcalloc(cd->hash_size, sizeof(struct hlist_head),
                                 GFP_KERNEL);
        if (cd->hash_table == NULL) {
                kfree(cd);
                return ERR_PTR(-ENOMEM);
        }

        for (i = 0; i < cd->hash_size; i++)
                INIT_HLIST_HEAD(&cd->hash_table[i]);
        cd->net = net;
        return cd;
}
EXPORT_SYMBOL_GPL(cache_create_net);

void cache_destroy_net(struct cache_detail *cd, struct net *net)
{
        kfree(cd->hash_table);
        kfree(cd);
}
EXPORT_SYMBOL_GPL(cache_destroy_net);

static ssize_t cache_read_pipefs(struct file *filp, char __user *buf,
                                 size_t count, loff_t *ppos)
{
        struct cache_detail *cd = RPC_I(file_inode(filp))->private;

        return cache_read(filp, buf, count, ppos, cd);
}

static ssize_t cache_write_pipefs(struct file *filp, const char __user *buf,
                                  size_t count, loff_t *ppos)
{
        struct cache_detail *cd = RPC_I(file_inode(filp))->private;

        return cache_write(filp, buf, count, ppos, cd);
}

static __poll_t cache_poll_pipefs(struct file *filp, poll_table *wait)
{
        struct cache_detail *cd = RPC_I(file_inode(filp))->private;

        return cache_poll(filp, wait, cd);
}

static long cache_ioctl_pipefs(struct file *filp,
                              unsigned int cmd, unsigned long arg)
{
        struct inode *inode = file_inode(filp);
        struct cache_detail *cd = RPC_I(inode)->private;

        return cache_ioctl(inode, filp, cmd, arg, cd);
}

static int cache_open_pipefs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = RPC_I(inode)->private;

        return cache_open(inode, filp, cd);
}

static int cache_release_pipefs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = RPC_I(inode)->private;

        return cache_release(inode, filp, cd);
}

const struct file_operations cache_file_operations_pipefs = {
        .owner          = THIS_MODULE,
        .read           = cache_read_pipefs,
        .write          = cache_write_pipefs,
        .poll           = cache_poll_pipefs,
        .unlocked_ioctl = cache_ioctl_pipefs, /* for FIONREAD */
        .open           = cache_open_pipefs,
        .release        = cache_release_pipefs,
};

static int content_open_pipefs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = RPC_I(inode)->private;

        return content_open(inode, filp, cd);
}

static int content_release_pipefs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = RPC_I(inode)->private;

        return content_release(inode, filp, cd);
}

const struct file_operations content_file_operations_pipefs = {
        .open           = content_open_pipefs,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = content_release_pipefs,
};

static int open_flush_pipefs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = RPC_I(inode)->private;

        return open_flush(inode, filp, cd);
}

static int release_flush_pipefs(struct inode *inode, struct file *filp)
{
        struct cache_detail *cd = RPC_I(inode)->private;

        return release_flush(inode, filp, cd);
}

static ssize_t read_flush_pipefs(struct file *filp, char __user *buf,
                            size_t count, loff_t *ppos)
{
        struct cache_detail *cd = RPC_I(file_inode(filp))->private;

        return read_flush(filp, buf, count, ppos, cd);
}

static ssize_t write_flush_pipefs(struct file *filp,
                                  const char __user *buf,
                                  size_t count, loff_t *ppos)
{
        struct cache_detail *cd = RPC_I(file_inode(filp))->private;

        return write_flush(filp, buf, count, ppos, cd);
}

const struct file_operations cache_flush_operations_pipefs = {
        .open           = open_flush_pipefs,
        .read           = read_flush_pipefs,
        .write          = write_flush_pipefs,
        .release        = release_flush_pipefs,
};

int sunrpc_cache_register_pipefs(struct dentry *parent,
                                 const char *name, umode_t umode,
                                 struct cache_detail *cd)
{
        struct dentry *dir = rpc_create_cache_dir(parent, name, umode, cd);
        if (IS_ERR(dir))
                return PTR_ERR(dir);
        cd->pipefs = dir;
        return 0;
}
EXPORT_SYMBOL_GPL(sunrpc_cache_register_pipefs);

void sunrpc_cache_unregister_pipefs(struct cache_detail *cd)
{
        if (cd->pipefs) {
                rpc_remove_cache_dir(cd->pipefs);
                cd->pipefs = NULL;
        }
}
EXPORT_SYMBOL_GPL(sunrpc_cache_unregister_pipefs);

void sunrpc_cache_unhash(struct cache_detail *cd, struct cache_head *h)
{
        spin_lock(&cd->hash_lock);
        if (!hlist_unhashed(&h->cache_list)){
                sunrpc_begin_cache_remove_entry(h, cd);
                spin_unlock(&cd->hash_lock);
                sunrpc_end_cache_remove_entry(h, cd);
        } else
                spin_unlock(&cd->hash_lock);
}
EXPORT_SYMBOL_GPL(sunrpc_cache_unhash);