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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * net/sunrpc/cache.c
  *
  * Generic code for various authentication-related caches
  * used by sunrpc clients and servers.
  *
  * Copyright (C) 2002 Neil Brown <neilb@cse.unsw.edu.au>
  */
 
 #include <linux/types.h>
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/slab.h>
 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/kmod.h>
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/ctype.h>
 #include <linux/string_helpers.h>
 #include <linux/uaccess.h>
 #include <linux/poll.h>
 #include <linux/seq_file.h>
 #include <linux/proc_fs.h>
 #include <linux/net.h>
 #include <linux/workqueue.h>
 #include <linux/mutex.h>
 #include <linux/pagemap.h>
 #include <asm/ioctls.h>
 #include <linux/sunrpc/types.h>
 #include <linux/sunrpc/cache.h>
 #include <linux/sunrpc/stats.h>
 #include <linux/sunrpc/rpc_pipe_fs.h>
 #include <trace/events/sunrpc.h>
 
 #include "netns.h"
 #include "fail.h"
 
 #define  RPCDBG_FACILITY RPCDBG_CACHE
 
 static bool cache_defer_req(struct cache_req *req, struct cache_head *item);
 static void cache_revisit_request(struct cache_head *item);
 
 static void cache_init(struct cache_head *h, struct cache_detail *detail)
 {
     time64_t now = seconds_since_boot();
     INIT_HLIST_NODE(&h->cache_list);
     h->flags = 0;
     kref_init(&h->ref);
     h->expiry_time = now + CACHE_NEW_EXPIRY;
     if (now <= detail->flush_time)
         /* ensure it isn't already expired */
         now = detail->flush_time + 1;
     h->last_refresh = now;
 }
 
 static void cache_fresh_unlocked(struct cache_head *head,
                 struct cache_detail *detail);
 
 static struct cache_head *sunrpc_cache_find_rcu(struct cache_detail *detail,
                         struct cache_head *key,
                         int hash)
 {
     struct hlist_head *head = &detail->hash_table[hash];
     struct cache_head *tmp;
 
     rcu_read_lock();
     hlist_for_each_entry_rcu(tmp, head, cache_list) {
         if (!detail->match(tmp, key))
             continue;
         if (test_bit(CACHE_VALID, &tmp->flags) &&
             cache_is_expired(detail, tmp))
             continue;
         tmp = cache_get_rcu(tmp);
         rcu_read_unlock();
         return tmp;
     }
     rcu_read_unlock();
     return NULL;
 }
 
 static void sunrpc_begin_cache_remove_entry(struct cache_head *ch,
                         struct cache_detail *cd)
 {
     /* Must be called under cd->hash_lock */
     hlist_del_init_rcu(&ch->cache_list);
     set_bit(CACHE_CLEANED, &ch->flags);
     cd->entries --;
 }
 
 static void sunrpc_end_cache_remove_entry(struct cache_head *ch,
                       struct cache_detail *cd)
 {
     cache_fresh_unlocked(ch, cd);
     cache_put(ch, cd);
 }
 
 static struct cache_head *sunrpc_cache_add_entry(struct cache_detail *detail,
                          struct cache_head *key,
                          int hash)
 {
     struct cache_head *new, *tmp, *freeme = NULL;
     struct hlist_head *head = &detail->hash_table[hash];
 
     new = detail->alloc();
     if (!new)
         return NULL;
     /* must fully initialise 'new', else
      * we might get lose if we need to
      * cache_put it soon.
      */
     cache_init(new, detail);
     detail->init(new, key);
 
     spin_lock(&detail->hash_lock);
 
     /* check if entry appeared while we slept */
     hlist_for_each_entry_rcu(tmp, head, cache_list,
                  lockdep_is_held(&detail->hash_lock)) {
         if (!detail->match(tmp, key))
             continue;
         if (test_bit(CACHE_VALID, &tmp->flags) &&
             cache_is_expired(detail, tmp)) {
             sunrpc_begin_cache_remove_entry(tmp, detail);
             trace_cache_entry_expired(detail, tmp);
             freeme = tmp;
             break;
         }
         cache_get(tmp);
         spin_unlock(&detail->hash_lock);
         cache_put(new, detail);
         return tmp;
     }
 
     hlist_add_head_rcu(&new->cache_list, head);
     detail->entries++;
     cache_get(new);
     spin_unlock(&detail->hash_lock);
 
     if (freeme)
         sunrpc_end_cache_remove_entry(freeme, detail);
     return new;
 }
 
 struct cache_head *sunrpc_cache_lookup_rcu(struct cache_detail *detail,
                        struct cache_head *key, int hash)
 {
     struct cache_head *ret;
 
     ret = sunrpc_cache_find_rcu(detail, key, hash);
     if (ret)
         return ret;
     /* Didn't find anything, insert an empty entry */
     return sunrpc_cache_add_entry(detail, key, hash);
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_lookup_rcu);
 
 static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch);
 
 static void cache_fresh_locked(struct cache_head *head, time64_t expiry,
                    struct cache_detail *detail)
 {
     time64_t now = seconds_since_boot();
     if (now <= detail->flush_time)
         /* ensure it isn't immediately treated as expired */
         now = detail->flush_time + 1;
     head->expiry_time = expiry;
     head->last_refresh = now;
     smp_wmb(); /* paired with smp_rmb() in cache_is_valid() */
     set_bit(CACHE_VALID, &head->flags);
 }
 
 static void cache_fresh_unlocked(struct cache_head *head,
                  struct cache_detail *detail)
 {
     if (test_and_clear_bit(CACHE_PENDING, &head->flags)) {
         cache_revisit_request(head);
         cache_dequeue(detail, head);
     }
 }
 
 static void cache_make_negative(struct cache_detail *detail,
                 struct cache_head *h)
 {
     set_bit(CACHE_NEGATIVE, &h->flags);
     trace_cache_entry_make_negative(detail, h);
 }
 
 static void cache_entry_update(struct cache_detail *detail,
                    struct cache_head *h,
                    struct cache_head *new)
 {
     if (!test_bit(CACHE_NEGATIVE, &new->flags)) {
         detail->update(h, new);
         trace_cache_entry_update(detail, h);
     } else {
         cache_make_negative(detail, h);
     }
 }
 
 struct cache_head *sunrpc_cache_update(struct cache_detail *detail,
                        struct cache_head *new, struct cache_head *old, int hash)
 {
     /* The 'old' entry is to be replaced by 'new'.
      * If 'old' is not VALID, we update it directly,
      * otherwise we need to replace it
      */
     struct cache_head *tmp;
 
     if (!test_bit(CACHE_VALID, &old->flags)) {
         spin_lock(&detail->hash_lock);
         if (!test_bit(CACHE_VALID, &old->flags)) {
             cache_entry_update(detail, old, new);
             cache_fresh_locked(old, new->expiry_time, detail);
             spin_unlock(&detail->hash_lock);
             cache_fresh_unlocked(old, detail);
             return old;
         }
         spin_unlock(&detail->hash_lock);
     }
     /* We need to insert a new entry */
     tmp = detail->alloc();
     if (!tmp) {
         cache_put(old, detail);
         return NULL;
     }
     cache_init(tmp, detail);
     detail->init(tmp, old);
 
     spin_lock(&detail->hash_lock);
     cache_entry_update(detail, tmp, new);
     hlist_add_head(&tmp->cache_list, &detail->hash_table[hash]);
     detail->entries++;
     cache_get(tmp);
     cache_fresh_locked(tmp, new->expiry_time, detail);
     cache_fresh_locked(old, 0, detail);
     spin_unlock(&detail->hash_lock);
     cache_fresh_unlocked(tmp, detail);
     cache_fresh_unlocked(old, detail);
     cache_put(old, detail);
     return tmp;
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_update);
 
 static inline int cache_is_valid(struct cache_head *h)
 {
     if (!test_bit(CACHE_VALID, &h->flags))
         return -EAGAIN;
     else {
         /* entry is valid */
         if (test_bit(CACHE_NEGATIVE, &h->flags))
             return -ENOENT;
         else {
             /*
              * In combination with write barrier in
              * sunrpc_cache_update, ensures that anyone
              * using the cache entry after this sees the
              * updated contents:
              */
             smp_rmb();
             return 0;
         }
     }
 }
 
 static int try_to_negate_entry(struct cache_detail *detail, struct cache_head *h)
 {
     int rv;
 
     spin_lock(&detail->hash_lock);
     rv = cache_is_valid(h);
     if (rv == -EAGAIN) {
         cache_make_negative(detail, h);
         cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY,
                    detail);
         rv = -ENOENT;
     }
     spin_unlock(&detail->hash_lock);
     cache_fresh_unlocked(h, detail);
     return rv;
 }
 
 /*
  * This is the generic cache management routine for all
  * the authentication caches.
  * It checks the currency of a cache item and will (later)
  * initiate an upcall to fill it if needed.
  *
  *
  * Returns 0 if the cache_head can be used, or cache_puts it and returns
  * -EAGAIN if upcall is pending and request has been queued
  * -ETIMEDOUT if upcall failed or request could not be queue or
  *           upcall completed but item is still invalid (implying that
  *           the cache item has been replaced with a newer one).
  * -ENOENT if cache entry was negative
  */
 int cache_check(struct cache_detail *detail,
             struct cache_head *h, struct cache_req *rqstp)
 {
     int rv;
     time64_t refresh_age, age;
 
     /* First decide return status as best we can */
     rv = cache_is_valid(h);
 
     /* now see if we want to start an upcall */
     refresh_age = (h->expiry_time - h->last_refresh);
     age = seconds_since_boot() - h->last_refresh;
 
     if (rqstp == NULL) {
         if (rv == -EAGAIN)
             rv = -ENOENT;
     } else if (rv == -EAGAIN ||
            (h->expiry_time != 0 && age > refresh_age/2)) {
         dprintk("RPC:       Want update, refage=%lld, age=%lld\n",
                 refresh_age, age);
         switch (detail->cache_upcall(detail, h)) {
         case -EINVAL:
             rv = try_to_negate_entry(detail, h);
             break;
         case -EAGAIN:
             cache_fresh_unlocked(h, detail);
             break;
         }
     }
 
     if (rv == -EAGAIN) {
         if (!cache_defer_req(rqstp, h)) {
             /*
              * Request was not deferred; handle it as best
              * we can ourselves:
              */
             rv = cache_is_valid(h);
             if (rv == -EAGAIN)
                 rv = -ETIMEDOUT;
         }
     }
     if (rv)
         cache_put(h, detail);
     return rv;
 }
 EXPORT_SYMBOL_GPL(cache_check);
 
 /*
  * caches need to be periodically cleaned.
  * For this we maintain a list of cache_detail and
  * a current pointer into that list and into the table
  * for that entry.
  *
  * Each time cache_clean is called it finds the next non-empty entry
  * in the current table and walks the list in that entry
  * looking for entries that can be removed.
  *
  * An entry gets removed if:
  * - The expiry is before current time
  * - The last_refresh time is before the flush_time for that cache
  *
  * later we might drop old entries with non-NEVER expiry if that table
  * is getting 'full' for some definition of 'full'
  *
  * The question of "how often to scan a table" is an interesting one
  * and is answered in part by the use of the "nextcheck" field in the
  * cache_detail.
  * When a scan of a table begins, the nextcheck field is set to a time
  * that is well into the future.
  * While scanning, if an expiry time is found that is earlier than the
  * current nextcheck time, nextcheck is set to that expiry time.
  * If the flush_time is ever set to a time earlier than the nextcheck
  * time, the nextcheck time is then set to that flush_time.
  *
  * A table is then only scanned if the current time is at least
  * the nextcheck time.
  *
  */
 
 static LIST_HEAD(cache_list);
 static DEFINE_SPINLOCK(cache_list_lock);
 static struct cache_detail *current_detail;
 static int current_index;
 
 static void do_cache_clean(struct work_struct *work);
 static struct delayed_work cache_cleaner;
 
 void sunrpc_init_cache_detail(struct cache_detail *cd)
 {
     spin_lock_init(&cd->hash_lock);
     INIT_LIST_HEAD(&cd->queue);
     spin_lock(&cache_list_lock);
     cd->nextcheck = 0;
     cd->entries = 0;
     atomic_set(&cd->writers, 0);
     cd->last_close = 0;
     cd->last_warn = -1;
     list_add(&cd->others, &cache_list);
     spin_unlock(&cache_list_lock);
 
     /* start the cleaning process */
     queue_delayed_work(system_power_efficient_wq, &cache_cleaner, 0);
 }
 EXPORT_SYMBOL_GPL(sunrpc_init_cache_detail);
 
 void sunrpc_destroy_cache_detail(struct cache_detail *cd)
 {
     cache_purge(cd);
     spin_lock(&cache_list_lock);
     spin_lock(&cd->hash_lock);
     if (current_detail == cd)
         current_detail = NULL;
     list_del_init(&cd->others);
     spin_unlock(&cd->hash_lock);
     spin_unlock(&cache_list_lock);
     if (list_empty(&cache_list)) {
         /* module must be being unloaded so its safe to kill the worker */
         cancel_delayed_work_sync(&cache_cleaner);
     }
 }
 EXPORT_SYMBOL_GPL(sunrpc_destroy_cache_detail);
 
 /* clean cache tries to find something to clean
  * and cleans it.
  * It returns 1 if it cleaned something,
  *            0 if it didn't find anything this time
  *           -1 if it fell off the end of the list.
  */
 static int cache_clean(void)
 {
     int rv = 0;
     struct list_head *next;
 
     spin_lock(&cache_list_lock);
 
     /* find a suitable table if we don't already have one */
     while (current_detail == NULL ||
         current_index >= current_detail->hash_size) {
         if (current_detail)
             next = current_detail->others.next;
         else
             next = cache_list.next;
         if (next == &cache_list) {
             current_detail = NULL;
             spin_unlock(&cache_list_lock);
             return -1;
         }
         current_detail = list_entry(next, struct cache_detail, others);
         if (current_detail->nextcheck > seconds_since_boot())
             current_index = current_detail->hash_size;
         else {
             current_index = 0;
             current_detail->nextcheck = seconds_since_boot()+30*60;
         }
     }
 
     /* find a non-empty bucket in the table */
     while (current_detail &&
            current_index < current_detail->hash_size &&
            hlist_empty(&current_detail->hash_table[current_index]))
         current_index++;
 
     /* find a cleanable entry in the bucket and clean it, or set to next bucket */
 
     if (current_detail && current_index < current_detail->hash_size) {
         struct cache_head *ch = NULL;
         struct cache_detail *d;
         struct hlist_head *head;
         struct hlist_node *tmp;
 
         spin_lock(&current_detail->hash_lock);
 
         /* Ok, now to clean this strand */
 
         head = &current_detail->hash_table[current_index];
         hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
             if (current_detail->nextcheck > ch->expiry_time)
                 current_detail->nextcheck = ch->expiry_time+1;
             if (!cache_is_expired(current_detail, ch))
                 continue;
 
             sunrpc_begin_cache_remove_entry(ch, current_detail);
             trace_cache_entry_expired(current_detail, ch);
             rv = 1;
             break;
         }
 
         spin_unlock(&current_detail->hash_lock);
         d = current_detail;
         if (!ch)
             current_index ++;
         spin_unlock(&cache_list_lock);
         if (ch)
             sunrpc_end_cache_remove_entry(ch, d);
     } else
         spin_unlock(&cache_list_lock);
 
     return rv;
 }
 
 /*
  * We want to regularly clean the cache, so we need to schedule some work ...
  */
 static void do_cache_clean(struct work_struct *work)
 {
     int delay;
 
     if (list_empty(&cache_list))
         return;
 
     if (cache_clean() == -1)
         delay = round_jiffies_relative(30*HZ);
     else
         delay = 5;
 
     queue_delayed_work(system_power_efficient_wq, &cache_cleaner, delay);
 }
 
 
 /*
  * Clean all caches promptly.  This just calls cache_clean
  * repeatedly until we are sure that every cache has had a chance to
  * be fully cleaned
  */
 void cache_flush(void)
 {
     while (cache_clean() != -1)
         cond_resched();
     while (cache_clean() != -1)
         cond_resched();
 }
 EXPORT_SYMBOL_GPL(cache_flush);
 
 void cache_purge(struct cache_detail *detail)
 {
     struct cache_head *ch = NULL;
     struct hlist_head *head = NULL;
     int i = 0;
 
     spin_lock(&detail->hash_lock);
     if (!detail->entries) {
         spin_unlock(&detail->hash_lock);
         return;
     }
 
     dprintk("RPC: %d entries in %s cache\n", detail->entries, detail->name);
     for (i = 0; i < detail->hash_size; i++) {
         head = &detail->hash_table[i];
         while (!hlist_empty(head)) {
             ch = hlist_entry(head->first, struct cache_head,
                      cache_list);
             sunrpc_begin_cache_remove_entry(ch, detail);
             spin_unlock(&detail->hash_lock);
             sunrpc_end_cache_remove_entry(ch, detail);
             spin_lock(&detail->hash_lock);
         }
     }
     spin_unlock(&detail->hash_lock);
 }
 EXPORT_SYMBOL_GPL(cache_purge);
 
 
 /*
  * Deferral and Revisiting of Requests.
  *
  * If a cache lookup finds a pending entry, we
  * need to defer the request and revisit it later.
  * All deferred requests are stored in a hash table,
  * indexed by "struct cache_head *".
  * As it may be wasteful to store a whole request
  * structure, we allow the request to provide a
  * deferred form, which must contain a
  * 'struct cache_deferred_req'
  * This cache_deferred_req contains a method to allow
  * it to be revisited when cache info is available
  */
 
 #define DFR_HASHSIZE    (PAGE_SIZE/sizeof(struct list_head))
 #define DFR_HASH(item)  ((((long)item)>>4 ^ (((long)item)>>13)) % DFR_HASHSIZE)
 
 #define DFR_MAX 300 /* ??? */
 
 static DEFINE_SPINLOCK(cache_defer_lock);
 static LIST_HEAD(cache_defer_list);
 static struct hlist_head cache_defer_hash[DFR_HASHSIZE];
 static int cache_defer_cnt;
 
 static void __unhash_deferred_req(struct cache_deferred_req *dreq)
 {
     hlist_del_init(&dreq->hash);
     if (!list_empty(&dreq->recent)) {
         list_del_init(&dreq->recent);
         cache_defer_cnt--;
     }
 }
 
 static void __hash_deferred_req(struct cache_deferred_req *dreq, struct cache_head *item)
 {
     int hash = DFR_HASH(item);
 
     INIT_LIST_HEAD(&dreq->recent);
     hlist_add_head(&dreq->hash, &cache_defer_hash[hash]);
 }
 
 static void setup_deferral(struct cache_deferred_req *dreq,
                struct cache_head *item,
                int count_me)
 {
 
     dreq->item = item;
 
     spin_lock(&cache_defer_lock);
 
     __hash_deferred_req(dreq, item);
 
     if (count_me) {
         cache_defer_cnt++;
         list_add(&dreq->recent, &cache_defer_list);
     }
 
     spin_unlock(&cache_defer_lock);
 
 }
 
 struct thread_deferred_req {
     struct cache_deferred_req handle;
     struct completion completion;
 };
 
 static void cache_restart_thread(struct cache_deferred_req *dreq, int too_many)
 {
     struct thread_deferred_req *dr =
         container_of(dreq, struct thread_deferred_req, handle);
     complete(&dr->completion);
 }
 
 static void cache_wait_req(struct cache_req *req, struct cache_head *item)
 {
     struct thread_deferred_req sleeper;
     struct cache_deferred_req *dreq = &sleeper.handle;
 
     sleeper.completion = COMPLETION_INITIALIZER_ONSTACK(sleeper.completion);
     dreq->revisit = cache_restart_thread;
 
     setup_deferral(dreq, item, 0);
 
     if (!test_bit(CACHE_PENDING, &item->flags) ||
         wait_for_completion_interruptible_timeout(
             &sleeper.completion, req->thread_wait) <= 0) {
         /* The completion wasn't completed, so we need
          * to clean up
          */
         spin_lock(&cache_defer_lock);
         if (!hlist_unhashed(&sleeper.handle.hash)) {
             __unhash_deferred_req(&sleeper.handle);
             spin_unlock(&cache_defer_lock);
         } else {
             /* cache_revisit_request already removed
              * this from the hash table, but hasn't
              * called ->revisit yet.  It will very soon
              * and we need to wait for it.
              */
             spin_unlock(&cache_defer_lock);
             wait_for_completion(&sleeper.completion);
         }
     }
 }
 
 static void cache_limit_defers(void)
 {
     /* Make sure we haven't exceed the limit of allowed deferred
      * requests.
      */
     struct cache_deferred_req *discard = NULL;
 
     if (cache_defer_cnt <= DFR_MAX)
         return;
 
     spin_lock(&cache_defer_lock);
 
     /* Consider removing either the first or the last */
     if (cache_defer_cnt > DFR_MAX) {
         if (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);
 }
 
 #if IS_ENABLED(CONFIG_FAIL_SUNRPC)
 static inline bool cache_defer_immediately(void)
 {
     return !fail_sunrpc.ignore_cache_wait &&
         should_fail(&fail_sunrpc.attr, 1);
 }
 #else
 static inline bool cache_defer_immediately(void)
 {
     return false;
 }
 #endif
 
 /* Return true if and only if a deferred request is queued. */
 static bool cache_defer_req(struct cache_req *req, struct cache_head *item)
 {
     struct cache_deferred_req *dreq;
 
     if (!cache_defer_immediately()) {
         cache_wait_req(req, item);
         if (!test_bit(CACHE_PENDING, &item->flags))
             return false;
     }
 
     dreq = req->defer(req);
     if (dreq == NULL)
         return false;
     setup_deferral(dreq, item, 1);
     if (!test_bit(CACHE_PENDING, &item->flags))
         /* Bit could have been cleared before we managed to
          * set up the deferral, so need to revisit just in case
          */
         cache_revisit_request(item);
 
     cache_limit_defers();
     return true;
 }
 
 static void cache_revisit_request(struct cache_head *item)
 {
     struct cache_deferred_req *dreq;
     struct 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);
 
 struct cache_queue {
     struct list_head    list;
     int         reader; /* if 0, then request */
 };
 struct cache_request {
     struct cache_queue  q;
     struct cache_head   *item;
     char            * buf;
     int         len;
     int         readers;
 };
 struct cache_reader {
     struct cache_queue  q;
     int         offset; /* if non-0, we have a refcnt on next request */
 };
 
 static int cache_request(struct cache_detail *detail,
                    struct cache_request *crq)
 {
     char *bp = crq->buf;
     int len = PAGE_SIZE;
 
     detail->cache_request(detail, crq->item, &bp, &len);
     if (len < 0)
         return -E2BIG;
     return PAGE_SIZE - len;
 }
 
 static ssize_t cache_read(struct file *filp, char __user *buf, size_t count,
               loff_t *ppos, struct cache_detail *cd)
 {
     struct cache_reader *rp = filp->private_data;
     struct cache_request *rq;
     struct inode *inode = file_inode(filp);
     int err;
 
     if (count == 0)
         return 0;
 
     inode_lock(inode); /* protect against multiple concurrent
                   * readers on this file */
  again:
     spin_lock(&queue_lock);
     /* need to find next request */
     while (rp->q.list.next != &cd->queue &&
            list_entry(rp->q.list.next, struct cache_queue, list)
            ->reader) {
         struct list_head *next = rp->q.list.next;
         list_move(&rp->q.list, next);
     }
     if (rp->q.list.next == &cd->queue) {
         spin_unlock(&queue_lock);
         inode_unlock(inode);
         WARN_ON_ONCE(rp->offset);
         return 0;
     }
     rq = container_of(rp->q.list.next, struct cache_request, q.list);
     WARN_ON_ONCE(rq->q.reader);
     if (rp->offset == 0)
         rq->readers++;
     spin_unlock(&queue_lock);
 
     if (rq->len == 0) {
         err = cache_request(cd, rq);
         if (err < 0)
             goto out;
         rq->len = err;
     }
 
     if (rp->offset == 0 && !test_bit(CACHE_PENDING, &rq->item->flags)) {
         err = -EAGAIN;
         spin_lock(&queue_lock);
         list_move(&rp->q.list, &rq->q.list);
         spin_unlock(&queue_lock);
     } else {
         if (rp->offset + count > rq->len)
             count = rq->len - rp->offset;
         err = -EFAULT;
         if (copy_to_user(buf, rq->buf + rp->offset, count))
             goto out;
         rp->offset += count;
         if (rp->offset >= rq->len) {
             rp->offset = 0;
             spin_lock(&queue_lock);
             list_move(&rp->q.list, &rq->q.list);
             spin_unlock(&queue_lock);
         }
         err = 0;
     }
  out:
     if (rp->offset == 0) {
         /* need to release rq */
         spin_lock(&queue_lock);
         rq->readers--;
         if (rq->readers == 0 &&
             !test_bit(CACHE_PENDING, &rq->item->flags)) {
             list_del(&rq->q.list);
             spin_unlock(&queue_lock);
             cache_put(rq->item, cd);
             kfree(rq->buf);
             kfree(rq);
         } else
             spin_unlock(&queue_lock);
     }
     if (err == -EAGAIN)
         goto again;
     inode_unlock(inode);
     return err ? err :  count;
 }
 
 static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
                  size_t count, struct cache_detail *cd)
 {
     ssize_t ret;
 
     if (count == 0)
         return -EINVAL;
     if (copy_from_user(kaddr, buf, count))
         return -EFAULT;
     kaddr[count] = '\0';
     ret = cd->cache_parse(cd, kaddr, count);
     if (!ret)
         ret = count;
     return ret;
 }
 
 static ssize_t cache_downcall(struct address_space *mapping,
                   const char __user *buf,
                   size_t count, struct cache_detail *cd)
 {
     char *write_buf;
     ssize_t ret = -ENOMEM;
 
     if (count >= 32768) { /* 32k is max userland buffer, lets check anyway */
         ret = -EINVAL;
         goto out;
     }
 
     write_buf = kvmalloc(count + 1, GFP_KERNEL);
     if (!write_buf)
         goto out;
 
     ret = cache_do_downcall(write_buf, buf, count, cd);
     kvfree(write_buf);
 out:
     return ret;
 }
 
 static ssize_t cache_write(struct file *filp, const char __user *buf,
                size_t count, loff_t *ppos,
                struct cache_detail *cd)
 {
     struct address_space *mapping = filp->f_mapping;
     struct inode *inode = file_inode(filp);
     ssize_t ret = -EINVAL;
 
     if (!cd->cache_parse)
         goto out;
 
     inode_lock(inode);
     ret = cache_downcall(mapping, buf, count, cd);
     inode_unlock(inode);
 out:
     return ret;
 }
 
 static DECLARE_WAIT_QUEUE_HEAD(queue_wait);
 
 static __poll_t cache_poll(struct file *filp, poll_table *wait,
                    struct cache_detail *cd)
 {
     __poll_t mask;
     struct cache_reader *rp = filp->private_data;
     struct cache_queue *cq;
 
     poll_wait(filp, &queue_wait, wait);
 
     /* alway allow write */
     mask = EPOLLOUT | EPOLLWRNORM;
 
     if (!rp)
         return mask;
 
     spin_lock(&queue_lock);
 
     for (cq= &rp->q; &cq->list != &cd->queue;
          cq = list_entry(cq->list.next, struct cache_queue, list))
         if (!cq->reader) {
             mask |= EPOLLIN | EPOLLRDNORM;
             break;
         }
     spin_unlock(&queue_lock);
     return mask;
 }
 
 static int cache_ioctl(struct inode *ino, struct file *filp,
                unsigned int cmd, unsigned long arg,
                struct cache_detail *cd)
 {
     int len = 0;
     struct cache_reader *rp = filp->private_data;
     struct cache_queue *cq;
 
     if (cmd != FIONREAD || !rp)
         return -EINVAL;
 
     spin_lock(&queue_lock);
 
     /* only find the length remaining in current request,
      * or the length of the next request
      */
     for (cq= &rp->q; &cq->list != &cd->queue;
          cq = list_entry(cq->list.next, struct cache_queue, list))
         if (!cq->reader) {
             struct cache_request *cr =
                 container_of(cq, struct cache_request, q);
             len = cr->len - rp->offset;
             break;
         }
     spin_unlock(&queue_lock);
 
     return put_user(len, (int __user *)arg);
 }
 
 static int cache_open(struct inode *inode, struct file *filp,
               struct cache_detail *cd)
 {
     struct cache_reader *rp = NULL;
 
     if (!cd || !try_module_get(cd->owner))
         return -EACCES;
     nonseekable_open(inode, filp);
     if (filp->f_mode & FMODE_READ) {
         rp = kmalloc(sizeof(*rp), GFP_KERNEL);
         if (!rp) {
             module_put(cd->owner);
             return -ENOMEM;
         }
         rp->offset = 0;
         rp->q.reader = 1;
 
         spin_lock(&queue_lock);
         list_add(&rp->q.list, &cd->queue);
         spin_unlock(&queue_lock);
     }
     if (filp->f_mode & FMODE_WRITE)
         atomic_inc(&cd->writers);
     filp->private_data = rp;
     return 0;
 }
 
 static int cache_release(struct inode *inode, struct file *filp,
              struct cache_detail *cd)
 {
     struct cache_reader *rp = filp->private_data;
 
     if (rp) {
         spin_lock(&queue_lock);
         if (rp->offset) {
             struct cache_queue *cq;
             for (cq= &rp->q; &cq->list != &cd->queue;
                  cq = list_entry(cq->list.next, struct cache_queue, list))
                 if (!cq->reader) {
                     container_of(cq, struct cache_request, q)
                         ->readers--;
                     break;
                 }
             rp->offset = 0;
         }
         list_del(&rp->q.list);
         spin_unlock(&queue_lock);
 
         filp->private_data = NULL;
         kfree(rp);
 
     }
     if (filp->f_mode & FMODE_WRITE) {
         atomic_dec(&cd->writers);
         cd->last_close = seconds_since_boot();
     }
     module_put(cd->owner);
     return 0;
 }
 
 
 
 static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch)
 {
     struct cache_queue *cq, *tmp;
     struct cache_request *cr;
     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->writers))
         return true;
     if (detail->last_close == 0)
         /* This cache was never opened */
         return false;
     if (detail->last_close < seconds_since_boot() - 30)
         /*
          * We allow for the possibility that someone might
          * restart a userspace daemon without restarting the
          * server; but after 30 seconds, we give up.
          */
          return false;
     return true;
 }
 
 /*
  * register an upcall request to user-space and queue it up for read() by the
  * upcall daemon.
  *
  * Each request is at most one page long.
  */
 static int cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h)
 {
     char *buf;
     struct cache_request *crq;
     int ret = 0;
 
     if (test_bit(CACHE_CLEANED, &h->flags))
         /* Too late to make an upcall */
         return -EAGAIN;
 
     buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
     if (!buf)
         return -EAGAIN;
 
     crq = kmalloc(sizeof (*crq), GFP_KERNEL);
     if (!crq) {
         kfree(buf);
         return -EAGAIN;
     }
 
     crq->q.reader = 0;
     crq->buf = buf;
     crq->len = 0;
     crq->readers = 0;
     spin_lock(&queue_lock);
     if (test_bit(CACHE_PENDING, &h->flags)) {
         crq->item = cache_get(h);
         list_add_tail(&crq->q.list, &detail->queue);
         trace_cache_entry_upcall(detail, h);
     } else
         /* Lost a race, no longer PENDING, so don't enqueue */
         ret = -EAGAIN;
     spin_unlock(&queue_lock);
     wake_up(&queue_wait);
     if (ret == -EAGAIN) {
         kfree(buf);
         kfree(crq);
     }
     return ret;
 }
 
 int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h)
 {
     if (test_and_set_bit(CACHE_PENDING, &h->flags))
         return 0;
     return cache_pipe_upcall(detail, h);
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_pipe_upcall);
 
 int sunrpc_cache_pipe_upcall_timeout(struct cache_detail *detail,
                      struct cache_head *h)
 {
     if (!cache_listeners_exist(detail)) {
         warn_no_listener(detail);
         trace_cache_entry_no_listener(detail, h);
         return -EINVAL;
     }
     return sunrpc_cache_pipe_upcall(detail, h);
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_pipe_upcall_timeout);
 
 /*
  * parse a message from user-space and pass it
  * to an appropriate cache
  * Messages are, like requests, separated into fields by
  * spaces and dequotes as \xHEXSTRING or embedded \nnn octal
  *
  * Message is
  *   reply cachename expiry key ... content....
  *
  * key and content are both parsed by cache
  */
 
 int qword_get(char **bpp, char *dest, int bufsize)
 {
     /* return bytes copied, or -1 on error */
     char *bp = *bpp;
     int len = 0;
 
     while (*bp == ' ') bp++;
 
     if (bp[0] == '\\' && bp[1] == 'x') {
         /* HEX STRING */
         bp += 2;
         while (len < bufsize - 1) {
             int h, l;
 
             h = hex_to_bin(bp[0]);
             if (h < 0)
                 break;
 
             l = hex_to_bin(bp[1]);
             if (l < 0)
                 break;
 
             *dest++ = (h << 4) | l;
             bp += 2;
             len++;
         }
     } else {
         /* text with \nnn octal quoting */
         while (*bp != ' ' && *bp != '\n' && *bp && len < bufsize-1) {
             if (*bp == '\\' &&
                 isodigit(bp[1]) && (bp[1] <= '3') &&
                 isodigit(bp[2]) &&
                 isodigit(bp[3])) {
                 int byte = (*++bp -'0');
                 bp++;
                 byte = (byte << 3) | (*bp++ - '0');
                 byte = (byte << 3) | (*bp++ - '0');
                 *dest++ = byte;
                 len++;
             } else {
                 *dest++ = *bp++;
                 len++;
             }
         }
     }
 
     if (*bp != ' ' && *bp != '\n' && *bp != '\0')
         return -1;
     while (*bp == ' ') bp++;
     *bpp = bp;
     *dest = '\0';
     return len;
 }
 EXPORT_SYMBOL_GPL(qword_get);
 
 
 /*
  * support /proc/net/rpc/$CACHENAME/content
  * as a seqfile.
  * We call ->cache_show passing NULL for the item to
  * get a header, then pass each real item in the cache
  */
 
 static void *__cache_seq_start(struct seq_file *m, loff_t *pos)
 {
     loff_t n = *pos;
     unsigned int hash, entry;
     struct cache_head *ch;
     struct cache_detail *cd = m->private;
 
     if (!n--)
         return SEQ_START_TOKEN;
     hash = n >> 32;
     entry = n & ((1LL<<32) - 1);
 
     hlist_for_each_entry_rcu(ch, &cd->hash_table[hash], cache_list)
         if (!entry--)
             return ch;
     n &= ~((1LL<<32) - 1);
     do {
         hash++;
         n += 1LL<<32;
     } while(hash < cd->hash_size &&
         hlist_empty(&cd->hash_table[hash]));
     if (hash >= cd->hash_size)
         return NULL;
     *pos = n+1;
     return hlist_entry_safe(rcu_dereference_raw(
                 hlist_first_rcu(&cd->hash_table[hash])),
                 struct cache_head, cache_list);
 }
 
 static void *cache_seq_next(struct seq_file *m, void *p, loff_t *pos)
 {
     struct cache_head *ch = p;
     int hash = (*pos >> 32);
     struct cache_detail *cd = m->private;
 
     if (p == SEQ_START_TOKEN)
         hash = 0;
     else if (ch->cache_list.next == NULL) {
         hash++;
         *pos += 1LL<<32;
     } else {
         ++*pos;
         return hlist_entry_safe(rcu_dereference_raw(
                     hlist_next_rcu(&ch->cache_list)),
                     struct cache_head, cache_list);
     }
     *pos &= ~((1LL<<32) - 1);
     while (hash < cd->hash_size &&
            hlist_empty(&cd->hash_table[hash])) {
         hash++;
         *pos += 1LL<<32;
     }
     if (hash >= cd->hash_size)
         return NULL;
     ++*pos;
     return hlist_entry_safe(rcu_dereference_raw(
                 hlist_first_rcu(&cd->hash_table[hash])),
                 struct cache_head, cache_list);
 }
 
 void *cache_seq_start_rcu(struct seq_file *m, loff_t *pos)
     __acquires(RCU)
 {
     rcu_read_lock();
     return __cache_seq_start(m, pos);
 }
 EXPORT_SYMBOL_GPL(cache_seq_start_rcu);
 
 void *cache_seq_next_rcu(struct seq_file *file, void *p, loff_t *pos)
 {
     return cache_seq_next(file, p, pos);
 }
 EXPORT_SYMBOL_GPL(cache_seq_next_rcu);
 
 void cache_seq_stop_rcu(struct seq_file *m, void *p)
     __releases(RCU)
 {
     rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(cache_seq_stop_rcu);
 
 static int c_show(struct seq_file *m, void *p)
 {
     struct cache_head *cp = p;
     struct cache_detail *cd = m->private;
 
     if (p == SEQ_START_TOKEN)
         return cd->cache_show(m, cd, NULL);
 
     ifdebug(CACHE)
         seq_printf(m, "# expiry=%lld refcnt=%d flags=%lx\n",
                convert_to_wallclock(cp->expiry_time),
                kref_read(&cp->ref), cp->flags);
     cache_get(cp);
     if (cache_check(cd, cp, NULL))
         /* cache_check does a cache_put on failure */
         seq_puts(m, "# ");
     else {
         if (cache_is_expired(cd, cp))
             seq_puts(m, "# ");
         cache_put(cp, cd);
     }
 
     return cd->cache_show(m, cd, cp);
 }
 
 static const struct seq_operations cache_content_op = {
     .start  = cache_seq_start_rcu,
     .next   = cache_seq_next_rcu,
     .stop   = cache_seq_stop_rcu,
     .show   = c_show,
 };
 
 static int content_open(struct inode *inode, struct file *file,
             struct cache_detail *cd)
 {
     struct seq_file *seq;
     int err;
 
     if (!cd || !try_module_get(cd->owner))
         return -EACCES;
 
     err = seq_open(file, &cache_content_op);
     if (err) {
         module_put(cd->owner);
         return err;
     }
 
     seq = file->private_data;
     seq->private = cd;
     return 0;
 }
 
 static int content_release(struct inode *inode, struct file *file,
         struct cache_detail *cd)
 {
     int ret = seq_release(inode, file);
     module_put(cd->owner);
     return ret;
 }
 
 static int open_flush(struct inode *inode, struct file *file,
             struct cache_detail *cd)
 {
     if (!cd || !try_module_get(cd->owner))
         return -EACCES;
     return nonseekable_open(inode, file);
 }
 
 static int release_flush(struct inode *inode, struct file *file,
             struct cache_detail *cd)
 {
     module_put(cd->owner);
     return 0;
 }
 
 static ssize_t read_flush(struct file *file, char __user *buf,
               size_t count, loff_t *ppos,
               struct cache_detail *cd)
 {
     char tbuf[22];
     size_t len;
 
     len = snprintf(tbuf, sizeof(tbuf), "%llu\n",
             convert_to_wallclock(cd->flush_time));
     return simple_read_from_buffer(buf, count, ppos, tbuf, len);
 }
 
 static ssize_t write_flush(struct file *file, const char __user *buf,
                size_t count, loff_t *ppos,
                struct cache_detail *cd)
 {
     char tbuf[20];
     char *ep;
     time64_t now;
 
     if (*ppos || count > sizeof(tbuf)-1)
         return -EINVAL;
     if (copy_from_user(tbuf, buf, count))
         return -EFAULT;
     tbuf[count] = 0;
     simple_strtoul(tbuf, &ep, 0);
     if (*ep && *ep != '\n')
         return -EINVAL;
     /* Note that while we check that 'buf' holds a valid number,
      * we always ignore the value and just flush everything.
      * Making use of the number leads to races.
      */
 
     now = seconds_since_boot();
     /* Always flush everything, so behave like cache_purge()
      * Do this by advancing flush_time to the current time,
      * or by one second if it has already reached the current time.
      * Newly added cache entries will always have ->last_refresh greater
      * that ->flush_time, so they don't get flushed prematurely.
      */
 
     if (cd->flush_time >= now)
         now = cd->flush_time + 1;
 
     cd->flush_time = now;
     cd->nextcheck = now;
     cache_flush();
 
     if (cd->flush)
         cd->flush();
 
     *ppos += count;
     return count;
 }
 
 static ssize_t cache_read_procfs(struct file *filp, char __user *buf,
                  size_t count, loff_t *ppos)
 {
     struct cache_detail *cd = pde_data(file_inode(filp));
 
     return cache_read(filp, buf, count, ppos, cd);
 }
 
 static ssize_t cache_write_procfs(struct file *filp, const char __user *buf,
                   size_t count, loff_t *ppos)
 {
     struct cache_detail *cd = pde_data(file_inode(filp));
 
     return cache_write(filp, buf, count, ppos, cd);
 }
 
 static __poll_t cache_poll_procfs(struct file *filp, poll_table *wait)
 {
     struct cache_detail *cd = pde_data(file_inode(filp));
 
     return cache_poll(filp, wait, cd);
 }
 
 static long cache_ioctl_procfs(struct file *filp,
                    unsigned int cmd, unsigned long arg)
 {
     struct inode *inode = file_inode(filp);
     struct cache_detail *cd = pde_data(inode);
 
     return cache_ioctl(inode, filp, cmd, arg, cd);
 }
 
 static int cache_open_procfs(struct inode *inode, struct file *filp)
 {
     struct cache_detail *cd = pde_data(inode);
 
     return cache_open(inode, filp, cd);
 }
 
 static int cache_release_procfs(struct inode *inode, struct file *filp)
 {
     struct cache_detail *cd = pde_data(inode);
 
     return cache_release(inode, filp, cd);
 }
 
 static const struct proc_ops cache_channel_proc_ops = {
     .proc_lseek = no_llseek,
     .proc_read  = cache_read_procfs,
     .proc_write = cache_write_procfs,
     .proc_poll  = cache_poll_procfs,
     .proc_ioctl = cache_ioctl_procfs, /* for FIONREAD */
     .proc_open  = cache_open_procfs,
     .proc_release   = cache_release_procfs,
 };
 
 static int content_open_procfs(struct inode *inode, struct file *filp)
 {
     struct cache_detail *cd = pde_data(inode);
 
     return content_open(inode, filp, cd);
 }
 
 static int content_release_procfs(struct inode *inode, struct file *filp)
 {
     struct cache_detail *cd = pde_data(inode);
 
     return content_release(inode, filp, cd);
 }
 
 static const struct proc_ops content_proc_ops = {
     .proc_open  = content_open_procfs,
     .proc_read  = seq_read,
     .proc_lseek = seq_lseek,
     .proc_release   = content_release_procfs,
 };
 
 static int open_flush_procfs(struct inode *inode, struct file *filp)
 {
     struct cache_detail *cd = pde_data(inode);
 
     return open_flush(inode, filp, cd);
 }
 
 static int release_flush_procfs(struct inode *inode, struct file *filp)
 {
     struct cache_detail *cd = pde_data(inode);
 
     return release_flush(inode, filp, cd);
 }
 
 static ssize_t read_flush_procfs(struct file *filp, char __user *buf,
                 size_t count, loff_t *ppos)
 {
     struct cache_detail *cd = pde_data(file_inode(filp));
 
     return read_flush(filp, buf, count, ppos, cd);
 }
 
 static ssize_t write_flush_procfs(struct file *filp,
                   const char __user *buf,
                   size_t count, loff_t *ppos)
 {
     struct cache_detail *cd = pde_data(file_inode(filp));
 
     return write_flush(filp, buf, count, ppos, cd);
 }
 
 static const struct proc_ops cache_flush_proc_ops = {
     .proc_open  = open_flush_procfs,
     .proc_read  = read_flush_procfs,
     .proc_write = write_flush_procfs,
     .proc_release   = release_flush_procfs,
     .proc_lseek = 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_proc_ops, cd);
     if (p == NULL)
         goto out_nomem;
 
     if (cd->cache_request || cd->cache_parse) {
         p = proc_create_data("channel", S_IFREG | 0600, cd->procfs,
                      &cache_channel_proc_ops, cd);
         if (p == NULL)
             goto out_nomem;
     }
     if (cd->cache_show) {
         p = proc_create_data("content", S_IFREG | 0400, cd->procfs,
                      &content_proc_ops, cd);
         if (p == NULL)
             goto out_nomem;
     }
     return 0;
 out_nomem:
     remove_cache_proc_entries(cd);
     return -ENOMEM;
 }
 #else /* CONFIG_PROC_FS */
 static int create_cache_proc_entries(struct cache_detail *cd, struct net *net)
 {
     return 0;
 }
 #endif
 
 void __init cache_initialize(void)
 {
     INIT_DEFERRABLE_WORK(&cache_cleaner, do_cache_clean);
 }
 
 int cache_register_net(struct cache_detail *cd, struct net *net)
 {
     int ret;
 
     sunrpc_init_cache_detail(cd);
     ret = create_cache_proc_entries(cd, net);
     if (ret)
         sunrpc_destroy_cache_detail(cd);
     return ret;
 }
 EXPORT_SYMBOL_GPL(cache_register_net);
 
 void cache_unregister_net(struct cache_detail *cd, struct net *net)
 {
     remove_cache_proc_entries(cd);
     sunrpc_destroy_cache_detail(cd);
 }
 EXPORT_SYMBOL_GPL(cache_unregister_net);
 
 struct cache_detail *cache_create_net(const struct cache_detail *tmpl, struct net *net)
 {
     struct cache_detail *cd;
     int i;
 
     cd = kmemdup(tmpl, sizeof(struct cache_detail), GFP_KERNEL);
     if (cd == NULL)
         return ERR_PTR(-ENOMEM);
 
     cd->hash_table = kcalloc(cd->hash_size, sizeof(struct hlist_head),
                  GFP_KERNEL);
     if (cd->hash_table == NULL) {
         kfree(cd);
         return ERR_PTR(-ENOMEM);
     }
 
     for (i = 0; i < cd->hash_size; i++)
         INIT_HLIST_HEAD(&cd->hash_table[i]);
     cd->net = net;
     return cd;
 }
 EXPORT_SYMBOL_GPL(cache_create_net);
 
 void cache_destroy_net(struct cache_detail *cd, struct net *net)
 {
     kfree(cd->hash_table);
     kfree(cd);
 }
 EXPORT_SYMBOL_GPL(cache_destroy_net);
 
 static ssize_t cache_read_pipefs(struct file *filp, char __user *buf,
                  size_t count, loff_t *ppos)
 {
     struct cache_detail *cd = RPC_I(file_inode(filp))->private;
 
     return cache_read(filp, buf, count, ppos, cd);
 }
 
 static ssize_t cache_write_pipefs(struct file *filp, const char __user *buf,
                   size_t count, loff_t *ppos)
 {
     struct cache_detail *cd = RPC_I(file_inode(filp))->private;
 
     return cache_write(filp, buf, count, ppos, cd);
 }
 
 static __poll_t cache_poll_pipefs(struct file *filp, poll_table *wait)
 {
     struct cache_detail *cd = RPC_I(file_inode(filp))->private;
 
     return cache_poll(filp, wait, cd);
 }
 
 static long cache_ioctl_pipefs(struct file *filp,
                   unsigned int cmd, unsigned long arg)
 {
     struct inode *inode = file_inode(filp);
     struct cache_detail *cd = RPC_I(inode)->private;
 
     return cache_ioctl(inode, filp, cmd, arg, cd);
 }
 
 static int cache_open_pipefs(struct inode *inode, struct file *filp)
 {
     struct cache_detail *cd = RPC_I(inode)->private;
 
     return cache_open(inode, filp, cd);
 }
 
 static int cache_release_pipefs(struct inode *inode, struct file *filp)
 {
     struct cache_detail *cd = RPC_I(inode)->private;
 
     return cache_release(inode, filp, cd);
 }
 
 const struct file_operations cache_file_operations_pipefs = {
     .owner      = THIS_MODULE,
     .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)){
         sunrpc_begin_cache_remove_entry(h, cd);
         spin_unlock(&cd->hash_lock);
         sunrpc_end_cache_remove_entry(h, cd);
     } else
         spin_unlock(&cd->hash_lock);
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_unhash);

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