text: // 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 "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 bool cache_listeners_exist(struct cache_detail *detail);
  
  static void cache_init(struct cache_head *h, struct cache_detail *detail)
  {
  	time_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 inline int cache_is_valid(struct cache_head *h);
  static void cache_fresh_locked(struct cache_head *head, time_t expiry,
  				struct cache_detail *detail);
  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)) {
  			if (cache_is_expired(detail, tmp))
  				continue;
  			tmp = cache_get_rcu(tmp);
  			rcu_read_unlock();
  			return tmp;
  		}
  	}
  	rcu_read_unlock();
  	return NULL;
  }
  
  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) {
  		if (detail->match(tmp, key)) {
  			if (cache_is_expired(detail, tmp)) {
  				hlist_del_init_rcu(&tmp->cache_list);
  				detail->entries --;
  				if (cache_is_valid(tmp) == -EAGAIN)
  					set_bit(CACHE_NEGATIVE, &tmp->flags);
  				cache_fresh_locked(tmp, 0, detail);
  				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) {
  		cache_fresh_unlocked(freeme, detail);
  		cache_put(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, time_t expiry,
  			       struct cache_detail *detail)
  {
  	time_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);
  	}
  }
  
  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)) {
  			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, 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);
  	if (test_bit(CACHE_NEGATIVE, &new->flags))
  		set_bit(CACHE_NEGATIVE, &tmp->flags);
  	else
  		detail->update(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 int cache_make_upcall(struct cache_detail *cd, struct cache_head *h)
  {
  	if (cd->cache_upcall)
  		return cd->cache_upcall(cd, h);
  	return sunrpc_cache_pipe_upcall(cd, h);
  }
  
  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) {
  		set_bit(CACHE_NEGATIVE, &h->flags);
  		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;
  	long 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=%ld, age=%ld\n",
  				refresh_age, age);
  		if (!test_and_set_bit(CACHE_PENDING, &h->flags)) {
  			switch (cache_make_upcall(detail, h)) {
  			case -EINVAL:
  				rv = try_to_negate_entry(detail, h);
  				break;
  			case -EAGAIN:
  				cache_fresh_unlocked(h, detail);
  				break;
  			}
  		} else if (!cache_listeners_exist(detail))
  			rv = try_to_negate_entry(detail, h);
  	}
  
  	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->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 */
  	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;
  
  			hlist_del_init_rcu(&ch->cache_list);
  			current_detail->entries--;
  			rv = 1;
  			break;
  		}
  
  		spin_unlock(&current_detail->hash_lock);
  		d = current_detail;
  		if (!ch)
  			current_index ++;
  		spin_unlock(&cache_list_lock);
  		if (ch) {
  			set_bit(CACHE_CLEANED, &ch->flags);
  			cache_fresh_unlocked(ch, d);
  			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)
  		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;
  	struct hlist_node *tmp = 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];
  		hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
  			hlist_del_init_rcu(&ch->cache_list);
  			detail->entries--;
  
  			set_bit(CACHE_CLEANED, &ch->flags);
  			spin_unlock(&detail->hash_lock);
  			cache_fresh_unlocked(ch, detail);
  			cache_put(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 (prandom_u32() & 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 *tmp;
  	int hash = DFR_HASH(item);
  
  	INIT_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;
  	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/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);
  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 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 -EAGAIN;
  	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_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_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);
  	put_page(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 = 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;
  		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, *tmp;
  	struct cache_request *cr;
  	struct list_head dequeued;
  
  	INIT_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->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)
  {
  
  	char *buf;
  	struct cache_request *crq;
  	int ret = 0;
  
  	if (!detail->cache_request)
  		return -EINVAL;
  
  	if (!cache_listeners_exist(detail)) {
  		warn_no_listener(detail);
  		return -EINVAL;
  	}
  	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);
  	} 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;
  }
  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
   */
  
  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);
  }
  EXPORT_SYMBOL_GPL(cache_seq_next);
  
  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=%ld 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_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	= 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), "%lu\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;
  	time_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();
  
  	*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 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_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 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_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 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)
  {
  	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_operations_procfs, 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_file_operations_procfs, cd);
  		if (p == NULL)
  			goto out_nomem;
  	}
  	if (cd->cache_show) {
  		p = proc_create_data("content", S_IFREG | 0400, cd->procfs,
  				     &content_file_operations_procfs, 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,
  	.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(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,
  	.llseek		= no_llseek,
  };
  
  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)){
  		hlist_del_init_rcu(&h->cache_list);
  		cd->entries--;
  		spin_unlock(&cd->hash_lock);
  		cache_put(h, cd);
  	} else
  		spin_unlock(&cd->hash_lock);
  }
  EXPORT_SYMBOL_GPL(sunrpc_cache_unhash);
  