/*
   * Open file cache.
   *
   * (c) 2015 - Jeff Layton <jeff.layton@primarydata.com>
   */
  
  #include <linux/hash.h>
  #include <linux/slab.h>

  #include <linux/file.h>
  #include <linux/sched.h>
  #include <linux/list_lru.h>
  #include <linux/fsnotify_backend.h>
  #include <linux/fsnotify.h>
  #include <linux/seq_file.h>
  
  #include "vfs.h"
  #include "nfsd.h"
  #include "nfsfh.h"

  #include "netns.h"

  #include "filecache.h"
  #include "trace.h"
  
  #define NFSDDBG_FACILITY	NFSDDBG_FH
  
  /* FIXME: dynamically size this for the machine somehow? */
  #define NFSD_FILE_HASH_BITS                   12
  #define NFSD_FILE_HASH_SIZE                  (1 << NFSD_FILE_HASH_BITS)
  #define NFSD_LAUNDRETTE_DELAY		     (2 * HZ)

  #define NFSD_FILE_SHUTDOWN		     (1)
  #define NFSD_FILE_LRU_THRESHOLD		     (4096UL)
  #define NFSD_FILE_LRU_LIMIT		     (NFSD_FILE_LRU_THRESHOLD << 2)
  
  /* We only care about NFSD_MAY_READ/WRITE for this cache */
  #define NFSD_FILE_MAY_MASK	(NFSD_MAY_READ|NFSD_MAY_WRITE)
  
  struct nfsd_fcache_bucket {
  	struct hlist_head	nfb_head;
  	spinlock_t		nfb_lock;
  	unsigned int		nfb_count;
  	unsigned int		nfb_maxcount;
  };
  
  static DEFINE_PER_CPU(unsigned long, nfsd_file_cache_hits);

  struct nfsd_fcache_disposal {
  	struct list_head list;
  	struct work_struct work;
  	struct net *net;
  	spinlock_t lock;
  	struct list_head freeme;
  	struct rcu_head rcu;
  };

  static struct workqueue_struct *nfsd_filecache_wq __read_mostly;

  static struct kmem_cache		*nfsd_file_slab;
  static struct kmem_cache		*nfsd_file_mark_slab;
  static struct nfsd_fcache_bucket	*nfsd_file_hashtbl;
  static struct list_lru			nfsd_file_lru;
  static long				nfsd_file_lru_flags;
  static struct fsnotify_group		*nfsd_file_fsnotify_group;
  static atomic_long_t			nfsd_filecache_count;
  static struct delayed_work		nfsd_filecache_laundrette;

  static DEFINE_SPINLOCK(laundrette_lock);
  static LIST_HEAD(laundrettes);

  static void nfsd_file_gc(void);

  
  static void

  nfsd_file_schedule_laundrette(void)

  {
  	long count = atomic_long_read(&nfsd_filecache_count);
  
  	if (count == 0 || test_bit(NFSD_FILE_SHUTDOWN, &nfsd_file_lru_flags))
  		return;

  	queue_delayed_work(system_wq, &nfsd_filecache_laundrette,
  			NFSD_LAUNDRETTE_DELAY);

  }
  
  static void
  nfsd_file_slab_free(struct rcu_head *rcu)
  {
  	struct nfsd_file *nf = container_of(rcu, struct nfsd_file, nf_rcu);
  
  	put_cred(nf->nf_cred);
  	kmem_cache_free(nfsd_file_slab, nf);
  }
  
  static void
  nfsd_file_mark_free(struct fsnotify_mark *mark)
  {
  	struct nfsd_file_mark *nfm = container_of(mark, struct nfsd_file_mark,
  						  nfm_mark);
  
  	kmem_cache_free(nfsd_file_mark_slab, nfm);
  }
  
  static struct nfsd_file_mark *
  nfsd_file_mark_get(struct nfsd_file_mark *nfm)
  {

  	if (!refcount_inc_not_zero(&nfm->nfm_ref))

  		return NULL;
  	return nfm;
  }
  
  static void
  nfsd_file_mark_put(struct nfsd_file_mark *nfm)
  {

  	if (refcount_dec_and_test(&nfm->nfm_ref)) {

  		fsnotify_destroy_mark(&nfm->nfm_mark, nfsd_file_fsnotify_group);
  		fsnotify_put_mark(&nfm->nfm_mark);
  	}
  }
  
  static struct nfsd_file_mark *
  nfsd_file_mark_find_or_create(struct nfsd_file *nf)
  {
  	int			err;
  	struct fsnotify_mark	*mark;
  	struct nfsd_file_mark	*nfm = NULL, *new;
  	struct inode *inode = nf->nf_inode;
  
  	do {
  		mutex_lock(&nfsd_file_fsnotify_group->mark_mutex);
  		mark = fsnotify_find_mark(&inode->i_fsnotify_marks,
  				nfsd_file_fsnotify_group);
  		if (mark) {
  			nfm = nfsd_file_mark_get(container_of(mark,
  						 struct nfsd_file_mark,
  						 nfm_mark));
  			mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex);

  			if (nfm) {
  				fsnotify_put_mark(mark);

  				break;

  			}
  			/* Avoid soft lockup race with nfsd_file_mark_put() */
  			fsnotify_destroy_mark(mark, nfsd_file_fsnotify_group);
  			fsnotify_put_mark(mark);

  		} else
  			mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex);
  
  		/* allocate a new nfm */
  		new = kmem_cache_alloc(nfsd_file_mark_slab, GFP_KERNEL);
  		if (!new)
  			return NULL;
  		fsnotify_init_mark(&new->nfm_mark, nfsd_file_fsnotify_group);
  		new->nfm_mark.mask = FS_ATTRIB|FS_DELETE_SELF;

  		refcount_set(&new->nfm_ref, 1);

  
  		err = fsnotify_add_inode_mark(&new->nfm_mark, inode, 0);
  
  		/*
  		 * If the add was successful, then return the object.
  		 * Otherwise, we need to put the reference we hold on the
  		 * nfm_mark. The fsnotify code will take a reference and put
  		 * it on failure, so we can't just free it directly. It's also
  		 * not safe to call fsnotify_destroy_mark on it as the
  		 * mark->group will be NULL. Thus, we can't let the nfm_ref
  		 * counter drive the destruction at this point.
  		 */
  		if (likely(!err))
  			nfm = new;
  		else
  			fsnotify_put_mark(&new->nfm_mark);
  	} while (unlikely(err == -EEXIST));
  
  	return nfm;
  }
  
  static struct nfsd_file *

  nfsd_file_alloc(struct inode *inode, unsigned int may, unsigned int hashval,
  		struct net *net)

  {
  	struct nfsd_file *nf;
  
  	nf = kmem_cache_alloc(nfsd_file_slab, GFP_KERNEL);
  	if (nf) {
  		INIT_HLIST_NODE(&nf->nf_node);
  		INIT_LIST_HEAD(&nf->nf_lru);
  		nf->nf_file = NULL;
  		nf->nf_cred = get_current_cred();

  		nf->nf_net = net;

  		nf->nf_flags = 0;
  		nf->nf_inode = inode;
  		nf->nf_hashval = hashval;

  		refcount_set(&nf->nf_ref, 1);

  		nf->nf_may = may & NFSD_FILE_MAY_MASK;
  		if (may & NFSD_MAY_NOT_BREAK_LEASE) {
  			if (may & NFSD_MAY_WRITE)
  				__set_bit(NFSD_FILE_BREAK_WRITE, &nf->nf_flags);
  			if (may & NFSD_MAY_READ)
  				__set_bit(NFSD_FILE_BREAK_READ, &nf->nf_flags);
  		}
  		nf->nf_mark = NULL;

  		init_rwsem(&nf->nf_rwsem);

  		trace_nfsd_file_alloc(nf);
  	}
  	return nf;
  }
  
  static bool
  nfsd_file_free(struct nfsd_file *nf)
  {
  	bool flush = false;
  
  	trace_nfsd_file_put_final(nf);
  	if (nf->nf_mark)
  		nfsd_file_mark_put(nf->nf_mark);
  	if (nf->nf_file) {
  		get_file(nf->nf_file);
  		filp_close(nf->nf_file, NULL);
  		fput(nf->nf_file);
  		flush = true;
  	}
  	call_rcu(&nf->nf_rcu, nfsd_file_slab_free);
  	return flush;
  }

  static bool
  nfsd_file_check_writeback(struct nfsd_file *nf)
  {
  	struct file *file = nf->nf_file;
  	struct address_space *mapping;
  
  	if (!file || !(file->f_mode & FMODE_WRITE))
  		return false;
  	mapping = file->f_mapping;
  	return mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) ||
  		mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK);
  }
  
  static int
  nfsd_file_check_write_error(struct nfsd_file *nf)
  {
  	struct file *file = nf->nf_file;
  
  	if (!file || !(file->f_mode & FMODE_WRITE))
  		return 0;
  	return filemap_check_wb_err(file->f_mapping, READ_ONCE(file->f_wb_err));
  }

  static void
  nfsd_file_do_unhash(struct nfsd_file *nf)
  {
  	lockdep_assert_held(&nfsd_file_hashtbl[nf->nf_hashval].nfb_lock);
  
  	trace_nfsd_file_unhash(nf);

  	if (nfsd_file_check_write_error(nf))
  		nfsd_reset_boot_verifier(net_generic(nf->nf_net, nfsd_net_id));

  	--nfsd_file_hashtbl[nf->nf_hashval].nfb_count;
  	hlist_del_rcu(&nf->nf_node);

  	atomic_long_dec(&nfsd_filecache_count);
  }
  
  static bool
  nfsd_file_unhash(struct nfsd_file *nf)
  {
  	if (test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
  		nfsd_file_do_unhash(nf);

  		if (!list_empty(&nf->nf_lru))
  			list_lru_del(&nfsd_file_lru, &nf->nf_lru);

  		return true;
  	}
  	return false;
  }
  
  /*
   * Return true if the file was unhashed.
   */
  static bool
  nfsd_file_unhash_and_release_locked(struct nfsd_file *nf, struct list_head *dispose)
  {
  	lockdep_assert_held(&nfsd_file_hashtbl[nf->nf_hashval].nfb_lock);
  
  	trace_nfsd_file_unhash_and_release_locked(nf);
  	if (!nfsd_file_unhash(nf))
  		return false;
  	/* keep final reference for nfsd_file_lru_dispose */

  	if (refcount_dec_not_one(&nf->nf_ref))

  		return true;
  
  	list_add(&nf->nf_lru, dispose);
  	return true;
  }

  static void

  nfsd_file_put_noref(struct nfsd_file *nf)
  {

  	trace_nfsd_file_put(nf);

  	if (refcount_dec_and_test(&nf->nf_ref)) {

  		WARN_ON(test_bit(NFSD_FILE_HASHED, &nf->nf_flags));
  		nfsd_file_free(nf);
  	}

  }
  
  void
  nfsd_file_put(struct nfsd_file *nf)
  {

  	bool is_hashed;

  
  	set_bit(NFSD_FILE_REFERENCED, &nf->nf_flags);

  	if (refcount_read(&nf->nf_ref) > 2 || !nf->nf_file) {

  		nfsd_file_put_noref(nf);
  		return;
  	}
  
  	filemap_flush(nf->nf_file->f_mapping);
  	is_hashed = test_bit(NFSD_FILE_HASHED, &nf->nf_flags) != 0;
  	nfsd_file_put_noref(nf);
  	if (is_hashed)

  		nfsd_file_schedule_laundrette();
  	if (atomic_long_read(&nfsd_filecache_count) >= NFSD_FILE_LRU_LIMIT)
  		nfsd_file_gc();

  }
  
  struct nfsd_file *
  nfsd_file_get(struct nfsd_file *nf)
  {

  	if (likely(refcount_inc_not_zero(&nf->nf_ref)))

  		return nf;
  	return NULL;
  }
  
  static void
  nfsd_file_dispose_list(struct list_head *dispose)
  {
  	struct nfsd_file *nf;
  
  	while(!list_empty(dispose)) {
  		nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
  		list_del(&nf->nf_lru);
  		nfsd_file_put_noref(nf);
  	}
  }
  
  static void
  nfsd_file_dispose_list_sync(struct list_head *dispose)
  {
  	bool flush = false;
  	struct nfsd_file *nf;
  
  	while(!list_empty(dispose)) {
  		nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
  		list_del(&nf->nf_lru);

  		if (!refcount_dec_and_test(&nf->nf_ref))

  			continue;
  		if (nfsd_file_free(nf))
  			flush = true;
  	}
  	if (flush)
  		flush_delayed_fput();
  }

  static void
  nfsd_file_list_remove_disposal(struct list_head *dst,
  		struct nfsd_fcache_disposal *l)
  {
  	spin_lock(&l->lock);
  	list_splice_init(&l->freeme, dst);
  	spin_unlock(&l->lock);
  }
  
  static void
  nfsd_file_list_add_disposal(struct list_head *files, struct net *net)
  {
  	struct nfsd_fcache_disposal *l;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(l, &laundrettes, list) {
  		if (l->net == net) {
  			spin_lock(&l->lock);
  			list_splice_tail_init(files, &l->freeme);
  			spin_unlock(&l->lock);
  			queue_work(nfsd_filecache_wq, &l->work);
  			break;
  		}
  	}
  	rcu_read_unlock();
  }
  
  static void
  nfsd_file_list_add_pernet(struct list_head *dst, struct list_head *src,
  		struct net *net)
  {
  	struct nfsd_file *nf, *tmp;
  
  	list_for_each_entry_safe(nf, tmp, src, nf_lru) {
  		if (nf->nf_net == net)
  			list_move_tail(&nf->nf_lru, dst);
  	}
  }
  
  static void
  nfsd_file_dispose_list_delayed(struct list_head *dispose)
  {
  	LIST_HEAD(list);
  	struct nfsd_file *nf;
  
  	while(!list_empty(dispose)) {
  		nf = list_first_entry(dispose, struct nfsd_file, nf_lru);
  		nfsd_file_list_add_pernet(&list, dispose, nf->nf_net);
  		nfsd_file_list_add_disposal(&list, nf->nf_net);
  	}
  }

  /*
   * Note this can deadlock with nfsd_file_cache_purge.
   */
  static enum lru_status
  nfsd_file_lru_cb(struct list_head *item, struct list_lru_one *lru,
  		 spinlock_t *lock, void *arg)
  	__releases(lock)
  	__acquires(lock)
  {
  	struct list_head *head = arg;
  	struct nfsd_file *nf = list_entry(item, struct nfsd_file, nf_lru);
  
  	/*
  	 * Do a lockless refcount check. The hashtable holds one reference, so
  	 * we look to see if anything else has a reference, or if any have
  	 * been put since the shrinker last ran. Those don't get unhashed and
  	 * released.
  	 *
  	 * Note that in the put path, we set the flag and then decrement the
  	 * counter. Here we check the counter and then test and clear the flag.
  	 * That order is deliberate to ensure that we can do this locklessly.
  	 */

  	if (refcount_read(&nf->nf_ref) > 1)

  		goto out_skip;

  
  	/*
  	 * Don't throw out files that are still undergoing I/O or
  	 * that have uncleared errors pending.
  	 */
  	if (nfsd_file_check_writeback(nf))
  		goto out_skip;

  	if (test_and_clear_bit(NFSD_FILE_REFERENCED, &nf->nf_flags))

  		goto out_skip;

  
  	if (!test_and_clear_bit(NFSD_FILE_HASHED, &nf->nf_flags))
  		goto out_skip;
  
  	list_lru_isolate_move(lru, &nf->nf_lru, head);
  	return LRU_REMOVED;

  out_skip:
  	return LRU_SKIP;
  }

  static unsigned long
  nfsd_file_lru_walk_list(struct shrink_control *sc)

  {

  	LIST_HEAD(head);

  	struct nfsd_file *nf;

  	unsigned long ret;

  	if (sc)
  		ret = list_lru_shrink_walk(&nfsd_file_lru, sc,
  				nfsd_file_lru_cb, &head);
  	else
  		ret = list_lru_walk(&nfsd_file_lru,
  				nfsd_file_lru_cb,
  				&head, LONG_MAX);
  	list_for_each_entry(nf, &head, nf_lru) {

  		spin_lock(&nfsd_file_hashtbl[nf->nf_hashval].nfb_lock);
  		nfsd_file_do_unhash(nf);
  		spin_unlock(&nfsd_file_hashtbl[nf->nf_hashval].nfb_lock);

  	}

  	nfsd_file_dispose_list_delayed(&head);
  	return ret;
  }
  
  static void
  nfsd_file_gc(void)
  {
  	nfsd_file_lru_walk_list(NULL);
  }
  
  static void
  nfsd_file_gc_worker(struct work_struct *work)
  {
  	nfsd_file_gc();
  	nfsd_file_schedule_laundrette();

  }
  
  static unsigned long
  nfsd_file_lru_count(struct shrinker *s, struct shrink_control *sc)
  {
  	return list_lru_count(&nfsd_file_lru);
  }
  
  static unsigned long
  nfsd_file_lru_scan(struct shrinker *s, struct shrink_control *sc)
  {

  	return nfsd_file_lru_walk_list(sc);

  }
  
  static struct shrinker	nfsd_file_shrinker = {
  	.scan_objects = nfsd_file_lru_scan,
  	.count_objects = nfsd_file_lru_count,
  	.seeks = 1,
  };
  
  static void
  __nfsd_file_close_inode(struct inode *inode, unsigned int hashval,
  			struct list_head *dispose)
  {
  	struct nfsd_file	*nf;
  	struct hlist_node	*tmp;
  
  	spin_lock(&nfsd_file_hashtbl[hashval].nfb_lock);
  	hlist_for_each_entry_safe(nf, tmp, &nfsd_file_hashtbl[hashval].nfb_head, nf_node) {
  		if (inode == nf->nf_inode)
  			nfsd_file_unhash_and_release_locked(nf, dispose);
  	}
  	spin_unlock(&nfsd_file_hashtbl[hashval].nfb_lock);
  }
  
  /**
   * nfsd_file_close_inode_sync - attempt to forcibly close a nfsd_file
   * @inode: inode of the file to attempt to remove
   *
   * Walk the whole hash bucket, looking for any files that correspond to "inode".
   * If any do, then unhash them and put the hashtable reference to them and
   * destroy any that had their last reference put. Also ensure that any of the
   * fputs also have their final __fput done as well.
   */
  void
  nfsd_file_close_inode_sync(struct inode *inode)
  {
  	unsigned int		hashval = (unsigned int)hash_long(inode->i_ino,
  						NFSD_FILE_HASH_BITS);
  	LIST_HEAD(dispose);
  
  	__nfsd_file_close_inode(inode, hashval, &dispose);
  	trace_nfsd_file_close_inode_sync(inode, hashval, !list_empty(&dispose));
  	nfsd_file_dispose_list_sync(&dispose);
  }
  
  /**
   * nfsd_file_close_inode_sync - attempt to forcibly close a nfsd_file
   * @inode: inode of the file to attempt to remove
   *
   * Walk the whole hash bucket, looking for any files that correspond to "inode".
   * If any do, then unhash them and put the hashtable reference to them and
   * destroy any that had their last reference put.
   */
  static void
  nfsd_file_close_inode(struct inode *inode)
  {
  	unsigned int		hashval = (unsigned int)hash_long(inode->i_ino,
  						NFSD_FILE_HASH_BITS);
  	LIST_HEAD(dispose);
  
  	__nfsd_file_close_inode(inode, hashval, &dispose);
  	trace_nfsd_file_close_inode(inode, hashval, !list_empty(&dispose));

  	nfsd_file_dispose_list_delayed(&dispose);

  }
  
  /**
   * nfsd_file_delayed_close - close unused nfsd_files
   * @work: dummy
   *
   * Walk the LRU list and close any entries that have not been used since
   * the last scan.
   *
   * Note this can deadlock with nfsd_file_cache_purge.
   */
  static void
  nfsd_file_delayed_close(struct work_struct *work)
  {
  	LIST_HEAD(head);

  	struct nfsd_fcache_disposal *l = container_of(work,
  			struct nfsd_fcache_disposal, work);

  	nfsd_file_list_remove_disposal(&head, l);
  	nfsd_file_dispose_list(&head);

  }
  
  static int
  nfsd_file_lease_notifier_call(struct notifier_block *nb, unsigned long arg,
  			    void *data)
  {
  	struct file_lock *fl = data;
  
  	/* Only close files for F_SETLEASE leases */
  	if (fl->fl_flags & FL_LEASE)
  		nfsd_file_close_inode_sync(file_inode(fl->fl_file));
  	return 0;
  }
  
  static struct notifier_block nfsd_file_lease_notifier = {
  	.notifier_call = nfsd_file_lease_notifier_call,
  };
  
  static int

  nfsd_file_fsnotify_handle_event(struct fsnotify_mark *mark, u32 mask,
  				struct inode *inode, struct inode *dir,

  				const struct qstr *name, u32 cookie)

  {
  	trace_nfsd_file_fsnotify_handle_event(inode, mask);
  
  	/* Should be no marks on non-regular files */
  	if (!S_ISREG(inode->i_mode)) {
  		WARN_ON_ONCE(1);
  		return 0;
  	}
  
  	/* don't close files if this was not the last link */
  	if (mask & FS_ATTRIB) {
  		if (inode->i_nlink)
  			return 0;
  	}
  
  	nfsd_file_close_inode(inode);
  	return 0;
  }
  
  
  static const struct fsnotify_ops nfsd_file_fsnotify_ops = {

  	.handle_inode_event = nfsd_file_fsnotify_handle_event,

  	.free_mark = nfsd_file_mark_free,
  };
  
  int
  nfsd_file_cache_init(void)
  {
  	int		ret = -ENOMEM;
  	unsigned int	i;
  
  	clear_bit(NFSD_FILE_SHUTDOWN, &nfsd_file_lru_flags);
  
  	if (nfsd_file_hashtbl)
  		return 0;

  	nfsd_filecache_wq = alloc_workqueue("nfsd_filecache", 0, 0);
  	if (!nfsd_filecache_wq)
  		goto out;

  	nfsd_file_hashtbl = kcalloc(NFSD_FILE_HASH_SIZE,
  				sizeof(*nfsd_file_hashtbl), GFP_KERNEL);
  	if (!nfsd_file_hashtbl) {
  		pr_err("nfsd: unable to allocate nfsd_file_hashtbl
  ");
  		goto out_err;
  	}
  
  	nfsd_file_slab = kmem_cache_create("nfsd_file",
  				sizeof(struct nfsd_file), 0, 0, NULL);
  	if (!nfsd_file_slab) {
  		pr_err("nfsd: unable to create nfsd_file_slab
  ");
  		goto out_err;
  	}
  
  	nfsd_file_mark_slab = kmem_cache_create("nfsd_file_mark",
  					sizeof(struct nfsd_file_mark), 0, 0, NULL);
  	if (!nfsd_file_mark_slab) {
  		pr_err("nfsd: unable to create nfsd_file_mark_slab
  ");
  		goto out_err;
  	}
  
  
  	ret = list_lru_init(&nfsd_file_lru);
  	if (ret) {
  		pr_err("nfsd: failed to init nfsd_file_lru: %d
  ", ret);
  		goto out_err;
  	}
  
  	ret = register_shrinker(&nfsd_file_shrinker);
  	if (ret) {
  		pr_err("nfsd: failed to register nfsd_file_shrinker: %d
  ", ret);
  		goto out_lru;
  	}
  
  	ret = lease_register_notifier(&nfsd_file_lease_notifier);
  	if (ret) {
  		pr_err("nfsd: unable to register lease notifier: %d
  ", ret);
  		goto out_shrinker;
  	}
  
  	nfsd_file_fsnotify_group = fsnotify_alloc_group(&nfsd_file_fsnotify_ops);
  	if (IS_ERR(nfsd_file_fsnotify_group)) {
  		pr_err("nfsd: unable to create fsnotify group: %ld
  ",
  			PTR_ERR(nfsd_file_fsnotify_group));
  		nfsd_file_fsnotify_group = NULL;
  		goto out_notifier;
  	}
  
  	for (i = 0; i < NFSD_FILE_HASH_SIZE; i++) {
  		INIT_HLIST_HEAD(&nfsd_file_hashtbl[i].nfb_head);
  		spin_lock_init(&nfsd_file_hashtbl[i].nfb_lock);
  	}

  	INIT_DELAYED_WORK(&nfsd_filecache_laundrette, nfsd_file_gc_worker);

  out:
  	return ret;
  out_notifier:
  	lease_unregister_notifier(&nfsd_file_lease_notifier);
  out_shrinker:
  	unregister_shrinker(&nfsd_file_shrinker);
  out_lru:
  	list_lru_destroy(&nfsd_file_lru);
  out_err:
  	kmem_cache_destroy(nfsd_file_slab);
  	nfsd_file_slab = NULL;
  	kmem_cache_destroy(nfsd_file_mark_slab);
  	nfsd_file_mark_slab = NULL;
  	kfree(nfsd_file_hashtbl);
  	nfsd_file_hashtbl = NULL;

  	destroy_workqueue(nfsd_filecache_wq);
  	nfsd_filecache_wq = NULL;

  	goto out;
  }
  
  /*
   * Note this can deadlock with nfsd_file_lru_cb.
   */
  void

  nfsd_file_cache_purge(struct net *net)

  {
  	unsigned int		i;
  	struct nfsd_file	*nf;

  	struct hlist_node	*next;

  	LIST_HEAD(dispose);
  	bool del;
  
  	if (!nfsd_file_hashtbl)
  		return;
  
  	for (i = 0; i < NFSD_FILE_HASH_SIZE; i++) {

  		struct nfsd_fcache_bucket *nfb = &nfsd_file_hashtbl[i];
  
  		spin_lock(&nfb->nfb_lock);
  		hlist_for_each_entry_safe(nf, next, &nfb->nfb_head, nf_node) {
  			if (net && nf->nf_net != net)
  				continue;

  			del = nfsd_file_unhash_and_release_locked(nf, &dispose);
  
  			/*
  			 * Deadlock detected! Something marked this entry as
  			 * unhased, but hasn't removed it from the hash list.
  			 */
  			WARN_ON_ONCE(!del);
  		}

  		spin_unlock(&nfb->nfb_lock);

  		nfsd_file_dispose_list(&dispose);
  	}
  }

  static struct nfsd_fcache_disposal *
  nfsd_alloc_fcache_disposal(struct net *net)
  {
  	struct nfsd_fcache_disposal *l;
  
  	l = kmalloc(sizeof(*l), GFP_KERNEL);
  	if (!l)
  		return NULL;
  	INIT_WORK(&l->work, nfsd_file_delayed_close);
  	l->net = net;
  	spin_lock_init(&l->lock);
  	INIT_LIST_HEAD(&l->freeme);
  	return l;
  }
  
  static void
  nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l)
  {
  	rcu_assign_pointer(l->net, NULL);
  	cancel_work_sync(&l->work);
  	nfsd_file_dispose_list(&l->freeme);
  	kfree_rcu(l, rcu);
  }
  
  static void
  nfsd_add_fcache_disposal(struct nfsd_fcache_disposal *l)
  {
  	spin_lock(&laundrette_lock);
  	list_add_tail_rcu(&l->list, &laundrettes);
  	spin_unlock(&laundrette_lock);
  }
  
  static void
  nfsd_del_fcache_disposal(struct nfsd_fcache_disposal *l)
  {
  	spin_lock(&laundrette_lock);
  	list_del_rcu(&l->list);
  	spin_unlock(&laundrette_lock);
  }
  
  static int
  nfsd_alloc_fcache_disposal_net(struct net *net)
  {
  	struct nfsd_fcache_disposal *l;
  
  	l = nfsd_alloc_fcache_disposal(net);
  	if (!l)
  		return -ENOMEM;
  	nfsd_add_fcache_disposal(l);
  	return 0;
  }
  
  static void
  nfsd_free_fcache_disposal_net(struct net *net)
  {
  	struct nfsd_fcache_disposal *l;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(l, &laundrettes, list) {
  		if (l->net != net)
  			continue;
  		nfsd_del_fcache_disposal(l);
  		rcu_read_unlock();
  		nfsd_free_fcache_disposal(l);
  		return;
  	}
  	rcu_read_unlock();
  }
  
  int
  nfsd_file_cache_start_net(struct net *net)
  {
  	return nfsd_alloc_fcache_disposal_net(net);
  }
  
  void
  nfsd_file_cache_shutdown_net(struct net *net)
  {
  	nfsd_file_cache_purge(net);
  	nfsd_free_fcache_disposal_net(net);
  }

  void
  nfsd_file_cache_shutdown(void)
  {

  	set_bit(NFSD_FILE_SHUTDOWN, &nfsd_file_lru_flags);
  
  	lease_unregister_notifier(&nfsd_file_lease_notifier);
  	unregister_shrinker(&nfsd_file_shrinker);
  	/*
  	 * make sure all callers of nfsd_file_lru_cb are done before
  	 * calling nfsd_file_cache_purge
  	 */
  	cancel_delayed_work_sync(&nfsd_filecache_laundrette);

  	nfsd_file_cache_purge(NULL);

  	list_lru_destroy(&nfsd_file_lru);
  	rcu_barrier();
  	fsnotify_put_group(nfsd_file_fsnotify_group);
  	nfsd_file_fsnotify_group = NULL;
  	kmem_cache_destroy(nfsd_file_slab);
  	nfsd_file_slab = NULL;
  	fsnotify_wait_marks_destroyed();
  	kmem_cache_destroy(nfsd_file_mark_slab);
  	nfsd_file_mark_slab = NULL;
  	kfree(nfsd_file_hashtbl);
  	nfsd_file_hashtbl = NULL;

  	destroy_workqueue(nfsd_filecache_wq);
  	nfsd_filecache_wq = NULL;

  }
  
  static bool
  nfsd_match_cred(const struct cred *c1, const struct cred *c2)
  {
  	int i;
  
  	if (!uid_eq(c1->fsuid, c2->fsuid))
  		return false;
  	if (!gid_eq(c1->fsgid, c2->fsgid))
  		return false;
  	if (c1->group_info == NULL || c2->group_info == NULL)
  		return c1->group_info == c2->group_info;
  	if (c1->group_info->ngroups != c2->group_info->ngroups)
  		return false;
  	for (i = 0; i < c1->group_info->ngroups; i++) {
  		if (!gid_eq(c1->group_info->gid[i], c2->group_info->gid[i]))
  			return false;
  	}
  	return true;
  }
  
  static struct nfsd_file *
  nfsd_file_find_locked(struct inode *inode, unsigned int may_flags,

  			unsigned int hashval, struct net *net)

  {
  	struct nfsd_file *nf;
  	unsigned char need = may_flags & NFSD_FILE_MAY_MASK;
  
  	hlist_for_each_entry_rcu(nf, &nfsd_file_hashtbl[hashval].nfb_head,

  				 nf_node, lockdep_is_held(&nfsd_file_hashtbl[hashval].nfb_lock)) {

  		if (nf->nf_may != need)

  			continue;
  		if (nf->nf_inode != inode)
  			continue;

  		if (nf->nf_net != net)
  			continue;

  		if (!nfsd_match_cred(nf->nf_cred, current_cred()))
  			continue;
  		if (nfsd_file_get(nf) != NULL)
  			return nf;
  	}
  	return NULL;
  }
  
  /**
   * nfsd_file_is_cached - are there any cached open files for this fh?
   * @inode: inode of the file to check
   *
   * Scan the hashtable for open files that match this fh. Returns true if there
   * are any, and false if not.
   */
  bool
  nfsd_file_is_cached(struct inode *inode)
  {
  	bool			ret = false;
  	struct nfsd_file	*nf;
  	unsigned int		hashval;
  
          hashval = (unsigned int)hash_long(inode->i_ino, NFSD_FILE_HASH_BITS);
  
  	rcu_read_lock();
  	hlist_for_each_entry_rcu(nf, &nfsd_file_hashtbl[hashval].nfb_head,
  				 nf_node) {
  		if (inode == nf->nf_inode) {
  			ret = true;
  			break;
  		}
  	}
  	rcu_read_unlock();
  	trace_nfsd_file_is_cached(inode, hashval, (int)ret);
  	return ret;
  }
  
  __be32
  nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
  		  unsigned int may_flags, struct nfsd_file **pnf)
  {
  	__be32	status;

  	struct net *net = SVC_NET(rqstp);

  	struct nfsd_file *nf, *new;
  	struct inode *inode;
  	unsigned int hashval;

  	bool retry = true;

  
  	/* FIXME: skip this if fh_dentry is already set? */
  	status = fh_verify(rqstp, fhp, S_IFREG,
  				may_flags|NFSD_MAY_OWNER_OVERRIDE);
  	if (status != nfs_ok)
  		return status;
  
  	inode = d_inode(fhp->fh_dentry);
  	hashval = (unsigned int)hash_long(inode->i_ino, NFSD_FILE_HASH_BITS);
  retry:
  	rcu_read_lock();

  	nf = nfsd_file_find_locked(inode, may_flags, hashval, net);

  	rcu_read_unlock();
  	if (nf)
  		goto wait_for_construction;

  	new = nfsd_file_alloc(inode, may_flags, hashval, net);

  	if (!new) {
  		trace_nfsd_file_acquire(rqstp, hashval, inode, may_flags,
  					NULL, nfserr_jukebox);
  		return nfserr_jukebox;
  	}
  
  	spin_lock(&nfsd_file_hashtbl[hashval].nfb_lock);

  	nf = nfsd_file_find_locked(inode, may_flags, hashval, net);

  	if (nf == NULL)
  		goto open_file;
  	spin_unlock(&nfsd_file_hashtbl[hashval].nfb_lock);
  	nfsd_file_slab_free(&new->nf_rcu);
  
  wait_for_construction:
  	wait_on_bit(&nf->nf_flags, NFSD_FILE_PENDING, TASK_UNINTERRUPTIBLE);
  
  	/* Did construction of this file fail? */
  	if (!test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {

  		if (!retry) {
  			status = nfserr_jukebox;
  			goto out;
  		}
  		retry = false;

  		nfsd_file_put_noref(nf);
  		goto retry;
  	}
  
  	this_cpu_inc(nfsd_file_cache_hits);
  
  	if (!(may_flags & NFSD_MAY_NOT_BREAK_LEASE)) {
  		bool write = (may_flags & NFSD_MAY_WRITE);
  
  		if (test_bit(NFSD_FILE_BREAK_READ, &nf->nf_flags) ||
  		    (test_bit(NFSD_FILE_BREAK_WRITE, &nf->nf_flags) && write)) {
  			status = nfserrno(nfsd_open_break_lease(
  					file_inode(nf->nf_file), may_flags));
  			if (status == nfs_ok) {
  				clear_bit(NFSD_FILE_BREAK_READ, &nf->nf_flags);
  				if (write)
  					clear_bit(NFSD_FILE_BREAK_WRITE,
  						  &nf->nf_flags);
  			}
  		}
  	}
  out:
  	if (status == nfs_ok) {
  		*pnf = nf;
  	} else {
  		nfsd_file_put(nf);
  		nf = NULL;
  	}
  
  	trace_nfsd_file_acquire(rqstp, hashval, inode, may_flags, nf, status);
  	return status;
  open_file:
  	nf = new;
  	/* Take reference for the hashtable */

  	refcount_inc(&nf->nf_ref);

  	__set_bit(NFSD_FILE_HASHED, &nf->nf_flags);
  	__set_bit(NFSD_FILE_PENDING, &nf->nf_flags);
  	list_lru_add(&nfsd_file_lru, &nf->nf_lru);
  	hlist_add_head_rcu(&nf->nf_node, &nfsd_file_hashtbl[hashval].nfb_head);
  	++nfsd_file_hashtbl[hashval].nfb_count;
  	nfsd_file_hashtbl[hashval].nfb_maxcount = max(nfsd_file_hashtbl[hashval].nfb_maxcount,
  			nfsd_file_hashtbl[hashval].nfb_count);
  	spin_unlock(&nfsd_file_hashtbl[hashval].nfb_lock);

  	if (atomic_long_inc_return(&nfsd_filecache_count) >= NFSD_FILE_LRU_THRESHOLD)
  		nfsd_file_gc();

  
  	nf->nf_mark = nfsd_file_mark_find_or_create(nf);
  	if (nf->nf_mark)
  		status = nfsd_open_verified(rqstp, fhp, S_IFREG,
  				may_flags, &nf->nf_file);
  	else
  		status = nfserr_jukebox;
  	/*
  	 * If construction failed, or we raced with a call to unlink()
  	 * then unhash.
  	 */
  	if (status != nfs_ok || inode->i_nlink == 0) {
  		bool do_free;
  		spin_lock(&nfsd_file_hashtbl[hashval].nfb_lock);
  		do_free = nfsd_file_unhash(nf);
  		spin_unlock(&nfsd_file_hashtbl[hashval].nfb_lock);
  		if (do_free)
  			nfsd_file_put_noref(nf);
  	}
  	clear_bit_unlock(NFSD_FILE_PENDING, &nf->nf_flags);
  	smp_mb__after_atomic();
  	wake_up_bit(&nf->nf_flags, NFSD_FILE_PENDING);
  	goto out;
  }
  
  /*
   * Note that fields may be added, removed or reordered in the future. Programs
   * scraping this file for info should test the labels to ensure they're
   * getting the correct field.
   */
  static int nfsd_file_cache_stats_show(struct seq_file *m, void *v)
  {
  	unsigned int i, count = 0, longest = 0;
  	unsigned long hits = 0;
  
  	/*
  	 * No need for spinlocks here since we're not terribly interested in
  	 * accuracy. We do take the nfsd_mutex simply to ensure that we
  	 * don't end up racing with server shutdown
  	 */
  	mutex_lock(&nfsd_mutex);
  	if (nfsd_file_hashtbl) {
  		for (i = 0; i < NFSD_FILE_HASH_SIZE; i++) {
  			count += nfsd_file_hashtbl[i].nfb_count;
  			longest = max(longest, nfsd_file_hashtbl[i].nfb_count);
  		}
  	}
  	mutex_unlock(&nfsd_mutex);
  
  	for_each_possible_cpu(i)
  		hits += per_cpu(nfsd_file_cache_hits, i);
  
  	seq_printf(m, "total entries: %u
  ", count);
  	seq_printf(m, "longest chain: %u
  ", longest);
  	seq_printf(m, "cache hits:    %lu
  ", hits);
  	return 0;
  }
  
  int nfsd_file_cache_stats_open(struct inode *inode, struct file *file)
  {
  	return single_open(file, nfsd_file_cache_stats_show, NULL);
  }