diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 8ca9a932d225..7dc55b93a830 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -21,6 +21,9 @@ struct kmem_cache *fscache_cookie_jar;
 
 static atomic_t fscache_object_debug_id = ATOMIC_INIT(0);
 
+#define fscache_cookie_hash_shift 15
+static struct hlist_bl_head fscache_cookie_hash[1 << fscache_cookie_hash_shift];
+
 static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie,
 					    loff_t object_size);
 static int fscache_alloc_object(struct fscache_cache *cache,
@@ -28,6 +31,44 @@ static int fscache_alloc_object(struct fscache_cache *cache,
 static int fscache_attach_object(struct fscache_cookie *cookie,
 				 struct fscache_object *object);
 
+static void fscache_print_cookie(struct fscache_cookie *cookie, char prefix)
+{
+	struct hlist_node *object;
+	const u8 *k;
+	unsigned loop;
+
+	pr_err("%c-cookie c=%p [p=%p fl=%lx nc=%u na=%u]\n",
+	       prefix, cookie, cookie->parent, cookie->flags,
+	       atomic_read(&cookie->n_children),
+	       atomic_read(&cookie->n_active));
+	pr_err("%c-cookie d=%p n=%p\n",
+	       prefix, cookie->def, cookie->netfs_data);
+
+	object = READ_ONCE(cookie->backing_objects.first);
+	if (object)
+		pr_err("%c-cookie o=%p\n",
+		       prefix, hlist_entry(object, struct fscache_object, cookie_link));
+
+	pr_err("%c-key=[%u] '", prefix, cookie->key_len);
+	k = (cookie->key_len <= sizeof(cookie->inline_key)) ?
+		cookie->inline_key : cookie->key;
+	for (loop = 0; loop < cookie->key_len; loop++)
+		pr_cont("%02x", k[loop]);
+	pr_cont("'\n");
+}
+
+void fscache_free_cookie(struct fscache_cookie *cookie)
+{
+	if (cookie) {
+		BUG_ON(!hlist_empty(&cookie->backing_objects));
+		if (cookie->aux_len > sizeof(cookie->inline_aux))
+			kfree(cookie->aux);
+		if (cookie->key_len > sizeof(cookie->inline_key))
+			kfree(cookie->key);
+		kmem_cache_free(fscache_cookie_jar, cookie);
+	}
+}
+
 /*
  * initialise an cookie jar slab element prior to any use
  */
@@ -41,6 +82,170 @@ void fscache_cookie_init_once(void *_cookie)
 	INIT_HLIST_HEAD(&cookie->backing_objects);
 }
 
+/*
+ * Set the index key in a cookie.  The cookie struct has space for a 12-byte
+ * key plus length and hash, but if that's not big enough, it's instead a
+ * pointer to a buffer containing 3 bytes of hash, 1 byte of length and then
+ * the key data.
+ */
+static int fscache_set_key(struct fscache_cookie *cookie,
+			   const void *index_key, size_t index_key_len)
+{
+	unsigned long long h;
+	u32 *buf;
+	int i;
+
+	cookie->key_len = index_key_len;
+
+	if (index_key_len > sizeof(cookie->inline_key)) {
+		buf = kzalloc(index_key_len, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+		cookie->key = buf;
+	} else {
+		buf = (u32 *)cookie->inline_key;
+		buf[0] = 0;
+		buf[1] = 0;
+		buf[2] = 0;
+	}
+
+	memcpy(buf, index_key, index_key_len);
+
+	/* Calculate a hash and combine this with the length in the first word
+	 * or first half word
+	 */
+	h = (unsigned long)cookie->parent;
+	h += index_key_len + cookie->type;
+	for (i = 0; i < (index_key_len + sizeof(u32) - 1) / sizeof(u32); i++)
+		h += buf[i];
+
+	cookie->key_hash = h ^ (h >> 32);
+	return 0;
+}
+
+static long fscache_compare_cookie(const struct fscache_cookie *a,
+				   const struct fscache_cookie *b)
+{
+	const void *ka, *kb;
+
+	if (a->key_hash != b->key_hash)
+		return (long)a->key_hash - (long)b->key_hash;
+	if (a->parent != b->parent)
+		return (long)a->parent - (long)b->parent;
+	if (a->key_len != b->key_len)
+		return (long)a->key_len - (long)b->key_len;
+	if (a->type != b->type)
+		return (long)a->type - (long)b->type;
+
+	if (a->key_len <= sizeof(a->inline_key)) {
+		ka = &a->inline_key;
+		kb = &b->inline_key;
+	} else {
+		ka = a->key;
+		kb = b->key;
+	}
+	return memcmp(ka, kb, a->key_len);
+}
+
+/*
+ * Allocate a cookie.
+ */
+struct fscache_cookie *fscache_alloc_cookie(
+	struct fscache_cookie *parent,
+	const struct fscache_cookie_def *def,
+	const void *index_key, size_t index_key_len,
+	const void *aux_data, size_t aux_data_len,
+	void *netfs_data,
+	loff_t object_size)
+{
+	struct fscache_cookie *cookie;
+
+	/* allocate and initialise a cookie */
+	cookie = kmem_cache_alloc(fscache_cookie_jar, GFP_KERNEL);
+	if (!cookie)
+		return NULL;
+
+	cookie->key_len = index_key_len;
+	cookie->aux_len = aux_data_len;
+
+	if (fscache_set_key(cookie, index_key, index_key_len) < 0)
+		goto nomem;
+
+	if (cookie->aux_len <= sizeof(cookie->inline_aux)) {
+		memcpy(cookie->inline_aux, aux_data, cookie->aux_len);
+	} else {
+		cookie->aux = kmemdup(aux_data, cookie->aux_len, GFP_KERNEL);
+		if (!cookie->aux)
+			goto nomem;
+	}
+
+	atomic_set(&cookie->usage, 1);
+	atomic_set(&cookie->n_children, 0);
+
+	/* We keep the active count elevated until relinquishment to prevent an
+	 * attempt to wake up every time the object operations queue quiesces.
+	 */
+	atomic_set(&cookie->n_active, 1);
+
+	cookie->def		= def;
+	cookie->parent		= parent;
+	cookie->netfs_data	= netfs_data;
+	cookie->flags		= (1 << FSCACHE_COOKIE_NO_DATA_YET);
+	cookie->type		= def->type;
+
+	/* radix tree insertion won't use the preallocation pool unless it's
+	 * told it may not wait */
+	INIT_RADIX_TREE(&cookie->stores, GFP_NOFS & ~__GFP_DIRECT_RECLAIM);
+	return cookie;
+
+nomem:
+	fscache_free_cookie(cookie);
+	return NULL;
+}
+
+/*
+ * Attempt to insert the new cookie into the hash.  If there's a collision, we
+ * return the old cookie if it's not in use and an error otherwise.
+ */
+struct fscache_cookie *fscache_hash_cookie(struct fscache_cookie *candidate)
+{
+	struct fscache_cookie *cursor;
+	struct hlist_bl_head *h;
+	struct hlist_bl_node *p;
+	unsigned int bucket;
+
+	bucket = candidate->key_hash & (ARRAY_SIZE(fscache_cookie_hash) - 1);
+	h = &fscache_cookie_hash[bucket];
+
+	hlist_bl_lock(h);
+	hlist_bl_for_each_entry(cursor, p, h, hash_link) {
+		if (fscache_compare_cookie(candidate, cursor) == 0)
+			goto collision;
+	}
+
+	__set_bit(FSCACHE_COOKIE_ACQUIRED, &candidate->flags);
+	fscache_cookie_get(candidate->parent, fscache_cookie_get_acquire_parent);
+	atomic_inc(&candidate->parent->n_children);
+	hlist_bl_add_head(&candidate->hash_link, h);
+	hlist_bl_unlock(h);
+	return candidate;
+
+collision:
+	if (test_and_set_bit(FSCACHE_COOKIE_ACQUIRED, &cursor->flags)) {
+		trace_fscache_cookie(cursor, fscache_cookie_collision,
+				     atomic_read(&cursor->usage));
+		pr_err("Duplicate cookie detected\n");
+		fscache_print_cookie(cursor, 'O');
+		fscache_print_cookie(candidate, 'N');
+		hlist_bl_unlock(h);
+		return NULL;
+	}
+
+	fscache_cookie_get(cursor, fscache_cookie_get_reacquire);
+	hlist_bl_unlock(h);
+	return cursor;
+}
+
 /*
  * request a cookie to represent an object (index, datafile, xattr, etc)
  * - parent specifies the parent object
@@ -65,7 +270,7 @@ struct fscache_cookie *__fscache_acquire_cookie(
 	loff_t object_size,
 	bool enable)
 {
-	struct fscache_cookie *cookie;
+	struct fscache_cookie *candidate, *cookie;
 
 	BUG_ON(!def);
 
@@ -95,53 +300,24 @@ struct fscache_cookie *__fscache_acquire_cookie(
 	BUG_ON(def->type == FSCACHE_COOKIE_TYPE_INDEX &&
 	       parent->type != FSCACHE_COOKIE_TYPE_INDEX);
 
-	/* allocate and initialise a cookie */
-	cookie = kmem_cache_alloc(fscache_cookie_jar, GFP_KERNEL);
-	if (!cookie) {
+	candidate = fscache_alloc_cookie(parent, def,
+					 index_key, index_key_len,
+					 aux_data, aux_data_len,
+					 netfs_data, object_size);
+	if (!candidate) {
 		fscache_stat(&fscache_n_acquires_oom);
 		_leave(" [ENOMEM]");
 		return NULL;
 	}
 
-	cookie->key_len		= index_key_len;
-	cookie->aux_len		= aux_data_len;
-
-	if (cookie->key_len <= sizeof(cookie->inline_key)) {
-		memcpy(cookie->inline_key, index_key, cookie->key_len);
-	} else {
-		cookie->key = kmemdup(index_key, cookie->key_len, GFP_KERNEL);
-		if (!cookie->key)
-			goto nomem;
+	cookie = fscache_hash_cookie(candidate);
+	if (!cookie) {
+		trace_fscache_cookie(candidate, fscache_cookie_discard, 1);
+		goto out;
 	}
 
-	if (cookie->aux_len <= sizeof(cookie->inline_aux)) {
-		memcpy(cookie->inline_aux, aux_data, cookie->aux_len);
-	} else {
-		cookie->aux = kmemdup(aux_data, cookie->aux_len, GFP_KERNEL);
-		if (!cookie->aux)
-			goto nomem;
-	}
-
-	atomic_set(&cookie->usage, 1);
-	atomic_set(&cookie->n_children, 0);
-
-	/* We keep the active count elevated until relinquishment to prevent an
-	 * attempt to wake up every time the object operations queue quiesces.
-	 */
-	atomic_set(&cookie->n_active, 1);
-
-	fscache_cookie_get(parent, fscache_cookie_get_acquire_parent);
-	atomic_inc(&parent->n_children);
-
-	cookie->def		= def;
-	cookie->parent		= parent;
-	cookie->netfs_data	= netfs_data;
-	cookie->flags		= (1 << FSCACHE_COOKIE_NO_DATA_YET);
-	cookie->type		= def->type;
-	
-	/* radix tree insertion won't use the preallocation pool unless it's
-	 * told it may not wait */
-	INIT_RADIX_TREE(&cookie->stores, GFP_NOFS & ~__GFP_DIRECT_RECLAIM);
+	if (cookie == candidate)
+		candidate = NULL;
 
 	switch (cookie->type) {
 	case FSCACHE_COOKIE_TYPE_INDEX:
@@ -178,16 +354,10 @@ struct fscache_cookie *__fscache_acquire_cookie(
 	}
 
 	fscache_stat(&fscache_n_acquires_ok);
-	_leave(" = %p", cookie);
-	return cookie;
 
-nomem:
-	if (cookie->aux_len > sizeof(cookie->inline_aux))
-		kfree(cookie->aux);
-	if (cookie->key_len > sizeof(cookie->inline_key))
-		kfree(cookie->key);
-	kmem_cache_free(fscache_cookie_jar, cookie);
-	return NULL;
+out:
+	fscache_free_cookie(candidate);
+	return cookie;
 }
 EXPORT_SYMBOL(__fscache_acquire_cookie);
 
@@ -678,6 +848,22 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie,
 }
 EXPORT_SYMBOL(__fscache_relinquish_cookie);
 
+/*
+ * Remove a cookie from the hash table.
+ */
+static void fscache_unhash_cookie(struct fscache_cookie *cookie)
+{
+	struct hlist_bl_head *h;
+	unsigned int bucket;
+
+	bucket = cookie->key_hash & (ARRAY_SIZE(fscache_cookie_hash) - 1);
+	h = &fscache_cookie_hash[bucket];
+
+	hlist_bl_lock(h);
+	hlist_bl_del(&cookie->hash_link);
+	hlist_bl_unlock(h);
+}
+
 /*
  * Drop a reference to a cookie.
  */
@@ -698,12 +884,8 @@ void fscache_cookie_put(struct fscache_cookie *cookie,
 		BUG_ON(usage < 0);
 
 		parent = cookie->parent;
-		BUG_ON(!hlist_empty(&cookie->backing_objects));
-		if (cookie->aux_len > sizeof(cookie->inline_aux))
-			kfree(cookie->aux);
-		if (cookie->key_len > sizeof(cookie->inline_key))
-			kfree(cookie->key);
-		kmem_cache_free(fscache_cookie_jar, cookie);
+		fscache_unhash_cookie(cookie);
+		fscache_free_cookie(cookie);
 
 		cookie = parent;
 		where = fscache_cookie_put_parent;
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 5f905a499306..500650f938fe 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -49,7 +49,14 @@ extern struct fscache_cache *fscache_select_cache_for_object(
  */
 extern struct kmem_cache *fscache_cookie_jar;
 
+extern void fscache_free_cookie(struct fscache_cookie *);
 extern void fscache_cookie_init_once(void *);
+extern struct fscache_cookie *fscache_alloc_cookie(struct fscache_cookie *,
+						   const struct fscache_cookie_def *,
+						   const void *, size_t,
+						   const void *, size_t,
+						   void *, loff_t);
+extern struct fscache_cookie *fscache_hash_cookie(struct fscache_cookie *);
 extern void fscache_cookie_put(struct fscache_cookie *,
 			       enum fscache_cookie_trace);
 
diff --git a/fs/fscache/netfs.c b/fs/fscache/netfs.c
index a5998dfab7e7..c2f605483cc5 100644
--- a/fs/fscache/netfs.c
+++ b/fs/fscache/netfs.c
@@ -14,85 +14,51 @@
 #include <linux/slab.h>
 #include "internal.h"
 
-static LIST_HEAD(fscache_netfs_list);
-
 /*
  * register a network filesystem for caching
  */
 int __fscache_register_netfs(struct fscache_netfs *netfs)
 {
-	struct fscache_netfs *ptr;
-	struct fscache_cookie *cookie;
-	int ret;
+	struct fscache_cookie *candidate, *cookie;
 
 	_enter("{%s}", netfs->name);
 
-	INIT_LIST_HEAD(&netfs->link);
-
 	/* allocate a cookie for the primary index */
-	cookie = kmem_cache_zalloc(fscache_cookie_jar, GFP_KERNEL);
-
-	if (!cookie) {
+	candidate = fscache_alloc_cookie(&fscache_fsdef_index,
+					 &fscache_fsdef_netfs_def,
+					 netfs->name, strlen(netfs->name),
+					 &netfs->version, sizeof(netfs->version),
+					 netfs, 0);
+	if (!candidate) {
 		_leave(" = -ENOMEM");
 		return -ENOMEM;
 	}
 
-	cookie->key_len = strlen(netfs->name);
-	if (cookie->key_len <= sizeof(cookie->inline_key)) {
-		memcpy(cookie->inline_key, netfs->name, strlen(netfs->name));
-	} else {
-		ret = -ENOMEM;
-		cookie->key = kmemdup(netfs->name, cookie->key_len, GFP_KERNEL);
-		if (!cookie->key)
-			goto nomem;
-	}
-
-	cookie->aux_len = sizeof(netfs->version);
-	memcpy(cookie->inline_aux, &netfs->version, cookie->aux_len);
-
-	/* initialise the primary index cookie */
-	atomic_set(&cookie->usage, 1);
-	atomic_set(&cookie->n_children, 0);
-	atomic_set(&cookie->n_active, 1);
-
-	cookie->def		= &fscache_fsdef_netfs_def;
-	cookie->parent		= &fscache_fsdef_index;
-	cookie->netfs_data	= netfs;
-	cookie->flags		= 1 << FSCACHE_COOKIE_ENABLED;
-	cookie->type		= FSCACHE_COOKIE_TYPE_INDEX;
-
-	spin_lock_init(&cookie->lock);
-	spin_lock_init(&cookie->stores_lock);
-	INIT_HLIST_HEAD(&cookie->backing_objects);
+	candidate->flags = 1 << FSCACHE_COOKIE_ENABLED;
 
 	/* check the netfs type is not already present */
-	down_write(&fscache_addremove_sem);
-
-	ret = -EEXIST;
-	list_for_each_entry(ptr, &fscache_netfs_list, link) {
-		if (strcmp(ptr->name, netfs->name) == 0)
-			goto already_registered;
+	cookie = fscache_hash_cookie(candidate);
+	if (!cookie)
+		goto already_registered;
+	if (cookie != candidate) {
+		trace_fscache_cookie(candidate, fscache_cookie_discard, 1);
+		fscache_free_cookie(candidate);
 	}
 
 	fscache_cookie_get(cookie->parent, fscache_cookie_get_register_netfs);
 	atomic_inc(&cookie->parent->n_children);
 
 	netfs->primary_index = cookie;
-	list_add(&netfs->link, &fscache_netfs_list);
-	ret = 0;
 
 	pr_notice("Netfs '%s' registered for caching\n", netfs->name);
 	trace_fscache_netfs(netfs);
+	_leave(" = 0");
+	return 0;
 
 already_registered:
-	up_write(&fscache_addremove_sem);
-
-nomem:
-	if (ret < 0)
-		kmem_cache_free(fscache_cookie_jar, cookie);
-
-	_leave(" = %d", ret);
-	return ret;
+	fscache_cookie_put(candidate, fscache_cookie_put_dup_netfs);
+	_leave(" = -EEXIST");
+	return -EEXIST;
 }
 EXPORT_SYMBOL(__fscache_register_netfs);
 
@@ -104,15 +70,8 @@ void __fscache_unregister_netfs(struct fscache_netfs *netfs)
 {
 	_enter("{%s.%u}", netfs->name, netfs->version);
 
-	down_write(&fscache_addremove_sem);
-
-	list_del(&netfs->link);
 	fscache_relinquish_cookie(netfs->primary_index, NULL, false);
-
-	up_write(&fscache_addremove_sem);
-
-	pr_notice("Netfs '%s' unregistered from caching\n",
-		  netfs->name);
+	pr_notice("Netfs '%s' unregistered from caching\n", netfs->name);
 
 	_leave("");
 }
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index eb38f39cf832..84b90a79d75a 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -22,6 +22,7 @@
 #include <linux/list.h>
 #include <linux/pagemap.h>
 #include <linux/pagevec.h>
+#include <linux/list_bl.h>
 
 #if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
 #define fscache_available() (1)
@@ -124,7 +125,6 @@ struct fscache_netfs {
 	uint32_t			version;	/* indexing version */
 	const char			*name;		/* filesystem name */
 	struct fscache_cookie		*primary_index;
-	struct list_head		link;		/* internal link */
 };
 
 /*
@@ -143,6 +143,7 @@ struct fscache_cookie {
 	struct hlist_head		backing_objects; /* object(s) backing this file/index */
 	const struct fscache_cookie_def	*def;		/* definition */
 	struct fscache_cookie		*parent;	/* parent of this entry */
+	struct hlist_bl_node		hash_link;	/* Link in hash table */
 	void				*netfs_data;	/* back pointer to netfs */
 	struct radix_tree_root		stores;		/* pages to be stored on this cookie */
 #define FSCACHE_COOKIE_PENDING_TAG	0		/* pages tag: pending write to cache */
@@ -156,11 +157,14 @@ struct fscache_cookie {
 #define FSCACHE_COOKIE_RELINQUISHED	4	/* T if cookie has been relinquished */
 #define FSCACHE_COOKIE_ENABLED		5	/* T if cookie is enabled */
 #define FSCACHE_COOKIE_ENABLEMENT_LOCK	6	/* T if cookie is being en/disabled */
-#define FSCACHE_COOKIE_AUX_UPDATED	7	/* T if the auxiliary data was updated */
+#define FSCACHE_COOKIE_AUX_UPDATED	8	/* T if the auxiliary data was updated */
+#define FSCACHE_COOKIE_ACQUIRED		9	/* T if cookie is in use */
+#define FSCACHE_COOKIE_RELINQUISHING	10	/* T if cookie is being relinquished */
 
 	u8				type;		/* Type of object */
 	u8				key_len;	/* Length of index key */
 	u8				aux_len;	/* Length of auxiliary data */
+	u32				key_hash;	/* Hash of parent, type, key, len */
 	union {
 		void			*key;		/* Index key */
 		u8			inline_key[16];	/* - If the key is short enough */
diff --git a/include/trace/events/fscache.h b/include/trace/events/fscache.h
index 82c060fe6635..686cfe997ed2 100644
--- a/include/trace/events/fscache.h
+++ b/include/trace/events/fscache.h
@@ -24,10 +24,14 @@
 #define __FSCACHE_DECLARE_TRACE_ENUMS_ONCE_ONLY
 
 enum fscache_cookie_trace {
+	fscache_cookie_collision,
+	fscache_cookie_discard,
 	fscache_cookie_get_acquire_parent,
 	fscache_cookie_get_attach_object,
+	fscache_cookie_get_reacquire,
 	fscache_cookie_get_register_netfs,
 	fscache_cookie_put_acquire_nobufs,
+	fscache_cookie_put_dup_netfs,
 	fscache_cookie_put_relinquish,
 	fscache_cookie_put_object,
 	fscache_cookie_put_parent,
@@ -86,10 +90,14 @@ enum fscache_page_op_trace {
  * Declare tracing information enums and their string mappings for display.
  */
 #define fscache_cookie_traces						\
+	EM(fscache_cookie_collision,		"*COLLISION*")		\
+	EM(fscache_cookie_discard,		"DISCARD")		\
 	EM(fscache_cookie_get_acquire_parent,	"GET prn")		\
 	EM(fscache_cookie_get_attach_object,	"GET obj")		\
+	EM(fscache_cookie_get_reacquire,	"GET raq")		\
 	EM(fscache_cookie_get_register_netfs,	"GET net")		\
 	EM(fscache_cookie_put_acquire_nobufs,	"PUT nbf")		\
+	EM(fscache_cookie_put_dup_netfs,	"PUT dnt")		\
 	EM(fscache_cookie_put_relinquish,	"PUT rlq")		\
 	EM(fscache_cookie_put_object,		"PUT obj")		\
 	E_(fscache_cookie_put_parent,		"PUT prn")