cache.c

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/*
 * net/sunrpc/cache.c
 *
 * Generic code for various authentication-related caches
 * used by sunrpc clients and servers.
 *
 * Copyright (C) 2002 Neil Brown <[email protected]>
 *
 * Released under terms in GPL version 2.  See COPYING.
 *
 */

#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 <asm/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 "netns.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)
{
    time_t now = seconds_since_boot();
    h->next = NULL;
    h->flags = 0;
    kref_init(&h->ref);
    h->expiry_time = now + CACHE_NEW_EXPIRY;
    h->last_refresh = now;
}

static inline int cache_is_expired(struct cache_detail *detail, struct cache_head *h)
{
    return  (h->expiry_time < seconds_since_boot()) ||
        (detail->flush_time > h->last_refresh);
}

struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
                       struct cache_head *key, int hash)
{
    struct cache_head **head,  **hp;
    struct cache_head *new = NULL, *freeme = NULL;

    head = &detail->hash_table[hash];

    read_lock(&detail->hash_lock);

    for (hp=head; *hp != NULL ; hp = &(*hp)->next) {
        struct cache_head *tmp = *hp;
        if (detail->match(tmp, key)) {
            if (cache_is_expired(detail, tmp))
                /* This entry is expired, we will discard it. */
                break;
            cache_get(tmp);
            read_unlock(&detail->hash_lock);
            return tmp;
        }
    }
    read_unlock(&detail->hash_lock);
    /* Didn't find anything, insert an empty entry */

    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->init(new, key);

    write_lock(&detail->hash_lock);

    /* check if entry appeared while we slept */
    for (hp=head; *hp != NULL ; hp = &(*hp)->next) {
        struct cache_head *tmp = *hp;
        if (detail->match(tmp, key)) {
            if (cache_is_expired(detail, tmp)) {
                *hp = tmp->next;
                tmp->next = NULL;
                detail->entries --;
                freeme = tmp;
                break;
            }
            cache_get(tmp);
            write_unlock(&detail->hash_lock);
            cache_put(new, detail);
            return tmp;
        }
    }
    new->next = *head;
    *head = new;
    detail->entries++;
    cache_get(new);
    write_unlock(&detail->hash_lock);

    if (freeme)
        cache_put(freeme, detail);
    return new;
}
EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);


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

static void cache_fresh_locked(struct cache_head *head, time_t expiry)
{
    head->expiry_time = expiry;
    head->last_refresh = seconds_since_boot();
    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);
    }
}

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 **head;
    struct cache_head *tmp;

    if (!test_bit(CACHE_VALID, &old->flags)) {
        write_lock(&detail->hash_lock);
        if (!test_bit(CACHE_VALID, &old->flags)) {
            if (test_bit(CACHE_NEGATIVE, &new->flags))
                set_bit(CACHE_NEGATIVE, &old->flags);
            else
                detail->update(old, new);
            cache_fresh_locked(old, new->expiry_time);
            write_unlock(&detail->hash_lock);
            cache_fresh_unlocked(old, detail);
            return old;
        }
        write_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->init(tmp, old);
    head = &detail->hash_table[hash];

    write_lock(&detail->hash_lock);
    if (test_bit(CACHE_NEGATIVE, &new->flags))
        set_bit(CACHE_NEGATIVE, &tmp->flags);
    else
        detail->update(tmp, new);
    tmp->next = *head;
    *head = tmp;
    detail->entries++;
    cache_get(tmp);
    cache_fresh_locked(tmp, new->expiry_time);
    cache_fresh_locked(old, 0);
    write_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 int cache_make_upcall(struct cache_detail *cd, struct cache_head *h)
{
    if (!cd->cache_upcall)
        return -EINVAL;
    return cd->cache_upcall(cd, h);
}

static inline int cache_is_valid(struct cache_detail *detail, 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;

    write_lock(&detail->hash_lock);
    rv = cache_is_valid(detail, h);
    if (rv != -EAGAIN) {
        write_unlock(&detail->hash_lock);
        return rv;
    }
    set_bit(CACHE_NEGATIVE, &h->flags);
    cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY);
    write_unlock(&detail->hash_lock);
    cache_fresh_unlocked(h, detail);
    return -ENOENT;
}

/*
 * 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;
    long refresh_age, age;

    /* First decide return status as best we can */
    rv = cache_is_valid(detail, 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 || age > refresh_age/2) {
        dprintk("RPC:       Want update, refage=%ld, age=%ld\n",
                refresh_age, age);
        if (!test_and_set_bit(CACHE_PENDING, &h->flags)) {
            switch (cache_make_upcall(detail, h)) {
            case -EINVAL:
                clear_bit(CACHE_PENDING, &h->flags);
                cache_revisit_request(h);
                rv = try_to_negate_entry(detail, h);
                break;
            case -EAGAIN:
                clear_bit(CACHE_PENDING, &h->flags);
                cache_revisit_request(h);
                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(detail, 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 clean_cache 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)
{
    rwlock_init(&cd->hash_lock);
    INIT_LIST_HEAD(&cd->queue);
    spin_lock(&cache_list_lock);
    cd->nextcheck = 0;
    cd->entries = 0;
    atomic_set(&cd->readers, 0);
    cd->last_close = 0;
    cd->last_warn = -1;
    list_add(&cd->others, &cache_list);
    spin_unlock(&cache_list_lock);

    /* start the cleaning process */
    schedule_delayed_work(&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);
    write_lock(&cd->hash_lock);
    if (cd->entries || atomic_read(&cd->inuse)) {
        write_unlock(&cd->hash_lock);
        spin_unlock(&cache_list_lock);
        goto out;
    }
    if (current_detail == cd)
        current_detail = NULL;
    list_del_init(&cd->others);
    write_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);
    }
    return;
out:
    printk(KERN_ERR "nfsd: failed to unregister %s cache\n", cd->name);
}
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 &&
           current_detail->hash_table[current_index] == NULL)
        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, **cp;
        struct cache_detail *d;

        write_lock(&current_detail->hash_lock);

        /* Ok, now to clean this strand */

        cp = & current_detail->hash_table[current_index];
        for (ch = *cp ; ch ; cp = & ch->next, ch = *cp) {
            if (current_detail->nextcheck > ch->expiry_time)
                current_detail->nextcheck = ch->expiry_time+1;
            if (!cache_is_expired(current_detail, ch))
                continue;

            *cp = ch->next;
            ch->next = NULL;
            current_detail->entries--;
            rv = 1;
            break;
        }

        write_unlock(&current_detail->hash_lock);
        d = current_detail;
        if (!ch)
            current_index ++;
        spin_unlock(&cache_list_lock);
        if (ch) {
            if (test_and_clear_bit(CACHE_PENDING, &ch->flags))
                cache_dequeue(current_detail, ch);
            cache_revisit_request(ch);
            cache_put(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 = 5;
    if (cache_clean() == -1)
        delay = round_jiffies_relative(30*HZ);

    if (list_empty(&cache_list))
        delay = 0;

    if (delay)
        schedule_delayed_work(&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)
{
    detail->flush_time = LONG_MAX;
    detail->nextcheck = seconds_since_boot();
    cache_flush();
    detail->flush_time = 1;
}
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 (net_random() & 1)
            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);
}

/* 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 (req->thread_wait) {
        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 list_head pending;
    struct hlist_node *lp, *tmp;
    int hash = DFR_HASH(item);

    INIT_LIST_HEAD(&pending);
    spin_lock(&cache_defer_lock);

    hlist_for_each_entry_safe(dreq, lp, 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;
    struct list_head pending;


    INIT_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/sunrpc/<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);
static DEFINE_MUTEX(queue_io_mutex);

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 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 = filp->f_path.dentry->d_inode;
    int err;

    if (count == 0)
        return 0;

    mutex_lock(&inode->i_mutex); /* 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);
        mutex_unlock(&inode->i_mutex);
        BUG_ON(rp->offset);
        return 0;
    }
    rq = container_of(rp->q.list.next, struct cache_request, q.list);
    BUG_ON(rq->q.reader);
    if (rp->offset == 0)
        rq->readers++;
    spin_unlock(&queue_lock);

    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;
    mutex_unlock(&inode->i_mutex);
    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_slow_downcall(const char __user *buf,
                   size_t count, struct cache_detail *cd)
{
    static char write_buf[8192]; /* protected by queue_io_mutex */
    ssize_t ret = -EINVAL;

    if (count >= sizeof(write_buf))
        goto out;
    mutex_lock(&queue_io_mutex);
    ret = cache_do_downcall(write_buf, buf, count, cd);
    mutex_unlock(&queue_io_mutex);
out:
    return ret;
}

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

    if (count >= PAGE_CACHE_SIZE)
        goto out_slow;

    page = find_or_create_page(mapping, 0, GFP_KERNEL);
    if (!page)
        goto out_slow;

    kaddr = kmap(page);
    ret = cache_do_downcall(kaddr, buf, count, cd);
    kunmap(page);
    unlock_page(page);
    page_cache_release(page);
    return ret;
out_slow:
    return cache_slow_downcall(buf, count, cd);
}

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 = filp->f_path.dentry->d_inode;
    ssize_t ret = -EINVAL;

    if (!cd->cache_parse)
        goto out;

    mutex_lock(&inode->i_mutex);
    ret = cache_downcall(mapping, buf, count, cd);
    mutex_unlock(&inode->i_mutex);
out:
    return ret;
}

static DECLARE_WAIT_QUEUE_HEAD(queue_wait);

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

    poll_wait(filp, &queue_wait, wait);

    /* alway allow write */
    mask = POLL_OUT | POLLWRNORM;

    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 |= POLLIN | POLLRDNORM;
            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)
            return -ENOMEM;
        rp->offset = 0;
        rp->q.reader = 1;
        atomic_inc(&cd->readers);
        spin_lock(&queue_lock);
        list_add(&rp->q.list, &cd->queue);
        spin_unlock(&queue_lock);
    }
    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);

        cd->last_close = seconds_since_boot();
        atomic_dec(&cd->readers);
    }
    module_put(cd->owner);
    return 0;
}



static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch)
{
    struct cache_queue *cq;
    spin_lock(&queue_lock);
    list_for_each_entry(cq, &detail->queue, list)
        if (!cq->reader) {
            struct cache_request *cr = container_of(cq, struct cache_request, q);
            if (cr->item != ch)
                continue;
            if (cr->readers != 0)
                continue;
            list_del(&cr->q.list);
            spin_unlock(&queue_lock);
            cache_put(cr->item, detail);
            kfree(cr->buf);
            kfree(cr);
            return;
        }
    spin_unlock(&queue_lock);
}

/*
 * 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;
    char c;

    if (len < 0) return;

    while ((c=*str++) && len)
        switch(c) {
        case ' ':
        case '\t':
        case '\n':
        case '\\':
            if (len >= 4) {
                *bp++ = '\\';
                *bp++ = '0' + ((c & 0300)>>6);
                *bp++ = '0' + ((c & 0070)>>3);
                *bp++ = '0' + ((c & 0007)>>0);
            }
            len -= 4;
            break;
        default:
            *bp++ = c;
            len--;
        }
    if (c || len <1) len = -1;
    else {
        *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) {
            unsigned char c = *buf++;
            *bp++ = '0' + ((c&0xf0)>>4) + (c>=0xa0)*('a'-'9'-1);
            *bp++ = '0' + (c&0x0f) + ((c&0x0f)>=0x0a)*('a'-'9'-1);
            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->readers))
        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.
 */
int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
        void (*cache_request)(struct cache_detail *,
                      struct cache_head *,
                      char **,
                      int *))
{

    char *buf;
    struct cache_request *crq;
    char *bp;
    int len;

    if (!cache_listeners_exist(detail)) {
        warn_no_listener(detail);
        return -EINVAL;
    }

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

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

    bp = buf; len = PAGE_SIZE;

    cache_request(detail, h, &bp, &len);

    if (len < 0) {
        kfree(buf);
        kfree(crq);
        return -EAGAIN;
    }
    crq->q.reader = 0;
    crq->item = cache_get(h);
    crq->buf = buf;
    crq->len = PAGE_SIZE - len;
    crq->readers = 0;
    spin_lock(&queue_lock);
    list_add_tail(&crq->q.list, &detail->queue);
    spin_unlock(&queue_lock);
    wake_up(&queue_wait);
    return 0;
}
EXPORT_SYMBOL_GPL(sunrpc_cache_pipe_upcall);

/*
 * 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
 */

#define isodigit(c) (isdigit(c) && c <= '7')
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) {
            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/sunrpc/cache/$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
 */

struct handle {
    struct cache_detail *cd;
};

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


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

    for (ch=cd->hash_table[hash]; ch; ch=ch->next)
        if (!entry--)
            return ch;
    n &= ~((1LL<<32) - 1);
    do {
        hash++;
        n += 1LL<<32;
    } while(hash < cd->hash_size &&
        cd->hash_table[hash]==NULL);
    if (hash >= cd->hash_size)
        return NULL;
    *pos = n+1;
    return cd->hash_table[hash];
}

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

    if (p == SEQ_START_TOKEN)
        hash = 0;
    else if (ch->next == NULL) {
        hash++;
        *pos += 1LL<<32;
    } else {
        ++*pos;
        return ch->next;
    }
    *pos &= ~((1LL<<32) - 1);
    while (hash < cd->hash_size &&
           cd->hash_table[hash] == NULL) {
        hash++;
        *pos += 1LL<<32;
    }
    if (hash >= cd->hash_size)
        return NULL;
    ++*pos;
    return cd->hash_table[hash];
}

static void c_stop(struct seq_file *m, void *p)
    __releases(cd->hash_lock)
{
    struct cache_detail *cd = ((struct handle*)m->private)->cd;
    read_unlock(&cd->hash_lock);
}

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

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

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

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

static const struct seq_operations cache_content_op = {
    .start  = c_start,
    .next   = c_next,
    .stop   = c_stop,
    .show   = c_show,
};

static int content_open(struct inode *inode, struct file *file,
            struct cache_detail *cd)
{
    struct handle *han;

    if (!cd || !try_module_get(cd->owner))
        return -EACCES;
    han = __seq_open_private(file, &cache_content_op, sizeof(*han));
    if (han == NULL) {
        module_put(cd->owner);
        return -ENOMEM;
    }

    han->cd = cd;
    return 0;
}

static int content_release(struct inode *inode, struct file *file,
        struct cache_detail *cd)
{
    int ret = seq_release_private(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];
    unsigned long p = *ppos;
    size_t len;

    snprintf(tbuf, sizeof(tbuf), "%lu\n", convert_to_wallclock(cd->flush_time));
    len = strlen(tbuf);
    if (p >= len)
        return 0;
    len -= p;
    if (len > count)
        len = count;
    if (copy_to_user(buf, (void*)(tbuf+p), len))
        return -EFAULT;
    *ppos += len;
    return 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 *bp, *ep;

    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;

    bp = tbuf;
    cd->flush_time = get_expiry(&bp);
    cd->nextcheck = seconds_since_boot();
    cache_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(filp->f_path.dentry->d_inode)->data;

    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(filp->f_path.dentry->d_inode)->data;

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

static unsigned int cache_poll_procfs(struct file *filp, poll_table *wait)
{
    struct cache_detail *cd = PDE(filp->f_path.dentry->d_inode)->data;

    return cache_poll(filp, wait, cd);
}

static long cache_ioctl_procfs(struct file *filp,
                   unsigned int cmd, unsigned long arg)
{
    struct inode *inode = filp->f_path.dentry->d_inode;
    struct cache_detail *cd = PDE(inode)->data;

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

static int cache_open_procfs(struct inode *inode, struct file *filp)
{
    struct cache_detail *cd = PDE(inode)->data;

    return cache_open(inode, filp, cd);
}

static int cache_release_procfs(struct inode *inode, struct file *filp)
{
    struct cache_detail *cd = PDE(inode)->data;

    return cache_release(inode, filp, cd);
}

static const struct file_operations cache_file_operations_procfs = {
    .owner      = THIS_MODULE,
    .llseek     = no_llseek,
    .read       = cache_read_procfs,
    .write      = cache_write_procfs,
    .poll       = cache_poll_procfs,
    .unlocked_ioctl = cache_ioctl_procfs, /* for FIONREAD */
    .open       = cache_open_procfs,
    .release    = cache_release_procfs,
};

static int content_open_procfs(struct inode *inode, struct file *filp)
{
    struct cache_detail *cd = PDE(inode)->data;

    return content_open(inode, filp, cd);
}

static int content_release_procfs(struct inode *inode, struct file *filp)
{
    struct cache_detail *cd = PDE(inode)->data;

    return content_release(inode, filp, cd);
}

static const struct file_operations content_file_operations_procfs = {
    .open       = content_open_procfs,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = content_release_procfs,
};

static int open_flush_procfs(struct inode *inode, struct file *filp)
{
    struct cache_detail *cd = PDE(inode)->data;

    return open_flush(inode, filp, cd);
}

static int release_flush_procfs(struct inode *inode, struct file *filp)
{
    struct cache_detail *cd = PDE(inode)->data;

    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(filp->f_path.dentry->d_inode)->data;

    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(filp->f_path.dentry->d_inode)->data;

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

static const struct file_operations cache_flush_operations_procfs = {
    .open       = open_flush_procfs,
    .read       = read_flush_procfs,
    .write      = write_flush_procfs,
    .release    = release_flush_procfs,
    .llseek     = no_llseek,
};

static void remove_cache_proc_entries(struct cache_detail *cd, struct net *net)
{
    struct sunrpc_net *sn;

    if (cd->u.procfs.proc_ent == NULL)
        return;
    if (cd->u.procfs.flush_ent)
        remove_proc_entry("flush", cd->u.procfs.proc_ent);
    if (cd->u.procfs.channel_ent)
        remove_proc_entry("channel", cd->u.procfs.proc_ent);
    if (cd->u.procfs.content_ent)
        remove_proc_entry("content", cd->u.procfs.proc_ent);
    cd->u.procfs.proc_ent = NULL;
    sn = net_generic(net, sunrpc_net_id);
    remove_proc_entry(cd->name, sn->proc_net_rpc);
}

#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->u.procfs.proc_ent = proc_mkdir(cd->name, sn->proc_net_rpc);
    if (cd->u.procfs.proc_ent == NULL)
        goto out_nomem;
    cd->u.procfs.channel_ent = NULL;
    cd->u.procfs.content_ent = NULL;

    p = proc_create_data("flush", S_IFREG|S_IRUSR|S_IWUSR,
                 cd->u.procfs.proc_ent,
                 &cache_flush_operations_procfs, cd);
    cd->u.procfs.flush_ent = p;
    if (p == NULL)
        goto out_nomem;

    if (cd->cache_upcall || cd->cache_parse) {
        p = proc_create_data("channel", S_IFREG|S_IRUSR|S_IWUSR,
                     cd->u.procfs.proc_ent,
                     &cache_file_operations_procfs, cd);
        cd->u.procfs.channel_ent = p;
        if (p == NULL)
            goto out_nomem;
    }
    if (cd->cache_show) {
        p = proc_create_data("content", S_IFREG|S_IRUSR|S_IWUSR,
                cd->u.procfs.proc_ent,
                &content_file_operations_procfs, cd);
        cd->u.procfs.content_ent = p;
        if (p == NULL)
            goto out_nomem;
    }
    return 0;
out_nomem:
    remove_cache_proc_entries(cd, net);
    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, net);
    sunrpc_destroy_cache_detail(cd);
}
EXPORT_SYMBOL_GPL(cache_unregister_net);

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

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

    cd->hash_table = kzalloc(cd->hash_size * sizeof(struct cache_head *),
                 GFP_KERNEL);
    if (cd->hash_table == NULL) {
        kfree(cd);
        return ERR_PTR(-ENOMEM);
    }
    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(filp->f_path.dentry->d_inode)->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(filp->f_path.dentry->d_inode)->private;

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

static unsigned int cache_poll_pipefs(struct file *filp, poll_table *wait)
{
    struct cache_detail *cd = RPC_I(filp->f_path.dentry->d_inode)->private;

    return cache_poll(filp, wait, cd);
}

static long cache_ioctl_pipefs(struct file *filp,
                  unsigned int cmd, unsigned long arg)
{
    struct inode *inode = filp->f_dentry->d_inode;
    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,
    .llseek     = no_llseek,
    .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(filp->f_path.dentry->d_inode)->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(filp->f_path.dentry->d_inode)->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,
    .llseek     = no_llseek,
};

int sunrpc_cache_register_pipefs(struct dentry *parent,
                 const char *name, umode_t umode,
                 struct cache_detail *cd)
{
    struct qstr q;
    struct dentry *dir;
    int ret = 0;

    q.name = name;
    q.len = strlen(name);
    q.hash = full_name_hash(q.name, q.len);
    dir = rpc_create_cache_dir(parent, &q, umode, cd);
    if (!IS_ERR(dir))
        cd->u.pipefs.dir = dir;
    else
        ret = PTR_ERR(dir);
    return ret;
}
EXPORT_SYMBOL_GPL(sunrpc_cache_register_pipefs);

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