1 files changed, 529 insertions, 144 deletions

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index ad1bc67aff1b..361a69dfe543 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -13,11 +13,12 @@
 #include <linux/bpf.h>
 #include <linux/jhash.h>
 #include <linux/filter.h>
-#include <linux/vmalloc.h>
+#include <linux/rculist_nulls.h>
 #include "percpu_freelist.h"
+#include "bpf_lru_list.h"
 
 struct bucket {
-	struct hlist_head head;
+	struct hlist_nulls_head head;
 	raw_spinlock_t lock;
 };
 
@@ -25,34 +26,55 @@ struct bpf_htab {
 	struct bpf_map map;
 	struct bucket *buckets;
 	void *elems;
-	struct pcpu_freelist freelist;
-	void __percpu *extra_elems;
+	union {
+		struct pcpu_freelist freelist;
+		struct bpf_lru lru;
+	};
+	struct htab_elem *__percpu *extra_elems;
 	atomic_t count;	/* number of elements in this hashtable */
 	u32 n_buckets;	/* number of hash buckets */
 	u32 elem_size;	/* size of each element in bytes */
 };
 
-enum extra_elem_state {
-	HTAB_NOT_AN_EXTRA_ELEM = 0,
-	HTAB_EXTRA_ELEM_FREE,
-	HTAB_EXTRA_ELEM_USED
-};
-
 /* each htab element is struct htab_elem + key + value */
 struct htab_elem {
 	union {
-		struct hlist_node hash_node;
-		struct bpf_htab *htab;
-		struct pcpu_freelist_node fnode;
+		struct hlist_nulls_node hash_node;
+		struct {
+			void *padding;
+			union {
+				struct bpf_htab *htab;
+				struct pcpu_freelist_node fnode;
+			};
+		};
 	};
 	union {
 		struct rcu_head rcu;
-		enum extra_elem_state state;
+		struct bpf_lru_node lru_node;
 	};
 	u32 hash;
 	char key[0] __aligned(8);
 };
 
+static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node);
+
+static bool htab_is_lru(const struct bpf_htab *htab)
+{
+	return htab->map.map_type == BPF_MAP_TYPE_LRU_HASH ||
+		htab->map.map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH;
+}
+
+static bool htab_is_percpu(const struct bpf_htab *htab)
+{
+	return htab->map.map_type == BPF_MAP_TYPE_PERCPU_HASH ||
+		htab->map.map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH;
+}
+
+static bool htab_is_prealloc(const struct bpf_htab *htab)
+{
+	return !(htab->map.map_flags & BPF_F_NO_PREALLOC);
+}
+
 static inline void htab_elem_set_ptr(struct htab_elem *l, u32 key_size,
 				     void __percpu *pptr)
 {
@@ -73,7 +95,7 @@ static void htab_free_elems(struct bpf_htab *htab)
 {
 	int i;
 
-	if (htab->map.map_type != BPF_MAP_TYPE_PERCPU_HASH)
+	if (!htab_is_percpu(htab))
 		goto free_elems;
 
 	for (i = 0; i < htab->map.max_entries; i++) {
@@ -84,21 +106,40 @@ static void htab_free_elems(struct bpf_htab *htab)
 		free_percpu(pptr);
 	}
 free_elems:
-	vfree(htab->elems);
+	bpf_map_area_free(htab->elems);
 }
 
-static int prealloc_elems_and_freelist(struct bpf_htab *htab)
+static struct htab_elem *prealloc_lru_pop(struct bpf_htab *htab, void *key,
+					  u32 hash)
 {
+	struct bpf_lru_node *node = bpf_lru_pop_free(&htab->lru, hash);
+	struct htab_elem *l;
+
+	if (node) {
+		l = container_of(node, struct htab_elem, lru_node);
+		memcpy(l->key, key, htab->map.key_size);
+		return l;
+	}
+
+	return NULL;
+}
+
+static int prealloc_init(struct bpf_htab *htab)
+{
+	u32 num_entries = htab->map.max_entries;
 	int err = -ENOMEM, i;
 
-	htab->elems = vzalloc(htab->elem_size * htab->map.max_entries);
+	if (!htab_is_percpu(htab) && !htab_is_lru(htab))
+		num_entries += num_possible_cpus();
+
+	htab->elems = bpf_map_area_alloc(htab->elem_size * num_entries);
 	if (!htab->elems)
 		return -ENOMEM;
 
-	if (htab->map.map_type != BPF_MAP_TYPE_PERCPU_HASH)
+	if (!htab_is_percpu(htab))
 		goto skip_percpu_elems;
 
-	for (i = 0; i < htab->map.max_entries; i++) {
+	for (i = 0; i < num_entries; i++) {
 		u32 size = round_up(htab->map.value_size, 8);
 		void __percpu *pptr;
 
@@ -110,12 +151,28 @@ static int prealloc_elems_and_freelist(struct bpf_htab *htab)
 	}
 
 skip_percpu_elems:
-	err = pcpu_freelist_init(&htab->freelist);
+	if (htab_is_lru(htab))
+		err = bpf_lru_init(&htab->lru,
+				   htab->map.map_flags & BPF_F_NO_COMMON_LRU,
+				   offsetof(struct htab_elem, hash) -
+				   offsetof(struct htab_elem, lru_node),
+				   htab_lru_map_delete_node,
+				   htab);
+	else
+		err = pcpu_freelist_init(&htab->freelist);
+
 	if (err)
 		goto free_elems;
 
-	pcpu_freelist_populate(&htab->freelist, htab->elems, htab->elem_size,
-			       htab->map.max_entries);
+	if (htab_is_lru(htab))
+		bpf_lru_populate(&htab->lru, htab->elems,
+				 offsetof(struct htab_elem, lru_node),
+				 htab->elem_size, num_entries);
+	else
+		pcpu_freelist_populate(&htab->freelist,
+				       htab->elems + offsetof(struct htab_elem, fnode),
+				       htab->elem_size, num_entries);
+
 	return 0;
 
 free_elems:
@@ -123,18 +180,34 @@ free_elems:
 	return err;
 }
 
+static void prealloc_destroy(struct bpf_htab *htab)
+{
+	htab_free_elems(htab);
+
+	if (htab_is_lru(htab))
+		bpf_lru_destroy(&htab->lru);
+	else
+		pcpu_freelist_destroy(&htab->freelist);
+}
+
 static int alloc_extra_elems(struct bpf_htab *htab)
 {
-	void __percpu *pptr;
+	struct htab_elem *__percpu *pptr, *l_new;
+	struct pcpu_freelist_node *l;
 	int cpu;
 
-	pptr = __alloc_percpu_gfp(htab->elem_size, 8, GFP_USER | __GFP_NOWARN);
+	pptr = __alloc_percpu_gfp(sizeof(struct htab_elem *), 8,
+				  GFP_USER | __GFP_NOWARN);
 	if (!pptr)
 		return -ENOMEM;
 
 	for_each_possible_cpu(cpu) {
-		((struct htab_elem *)per_cpu_ptr(pptr, cpu))->state =
-			HTAB_EXTRA_ELEM_FREE;
+		l = pcpu_freelist_pop(&htab->freelist);
+		/* pop will succeed, since prealloc_init()
+		 * preallocated extra num_possible_cpus elements
+		 */
+		l_new = container_of(l, struct htab_elem, fnode);
+		*per_cpu_ptr(pptr, cpu) = l_new;
 	}
 	htab->extra_elems = pptr;
 	return 0;
@@ -143,15 +216,42 @@ static int alloc_extra_elems(struct bpf_htab *htab)
 /* Called from syscall */
 static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 {
-	bool percpu = attr->map_type == BPF_MAP_TYPE_PERCPU_HASH;
+	bool percpu = (attr->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
+		       attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
+	bool lru = (attr->map_type == BPF_MAP_TYPE_LRU_HASH ||
+		    attr->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH);
+	/* percpu_lru means each cpu has its own LRU list.
+	 * it is different from BPF_MAP_TYPE_PERCPU_HASH where
+	 * the map's value itself is percpu.  percpu_lru has
+	 * nothing to do with the map's value.
+	 */
+	bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
+	bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
 	struct bpf_htab *htab;
 	int err, i;
 	u64 cost;
 
-	if (attr->map_flags & ~BPF_F_NO_PREALLOC)
+	BUILD_BUG_ON(offsetof(struct htab_elem, htab) !=
+		     offsetof(struct htab_elem, hash_node.pprev));
+	BUILD_BUG_ON(offsetof(struct htab_elem, fnode.next) !=
+		     offsetof(struct htab_elem, hash_node.pprev));
+
+	if (lru && !capable(CAP_SYS_ADMIN))
+		/* LRU implementation is much complicated than other
+		 * maps.  Hence, limit to CAP_SYS_ADMIN for now.
+		 */
+		return ERR_PTR(-EPERM);
+
+	if (attr->map_flags & ~(BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU))
 		/* reserved bits should not be used */
 		return ERR_PTR(-EINVAL);
 
+	if (!lru && percpu_lru)
+		return ERR_PTR(-EINVAL);
+
+	if (lru && !prealloc)
+		return ERR_PTR(-ENOTSUPP);
+
 	htab = kzalloc(sizeof(*htab), GFP_USER);
 	if (!htab)
 		return ERR_PTR(-ENOMEM);
@@ -171,6 +271,18 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 	    htab->map.value_size == 0)
 		goto free_htab;
 
+	if (percpu_lru) {
+		/* ensure each CPU's lru list has >=1 elements.
+		 * since we are at it, make each lru list has the same
+		 * number of elements.
+		 */
+		htab->map.max_entries = roundup(attr->max_entries,
+						num_possible_cpus());
+		if (htab->map.max_entries < attr->max_entries)
+			htab->map.max_entries = rounddown(attr->max_entries,
+							  num_possible_cpus());
+	}
+
 	/* hash table size must be power of 2 */
 	htab->n_buckets = roundup_pow_of_two(htab->map.max_entries);
 
@@ -181,7 +293,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 		 */
 		goto free_htab;
 
-	if (htab->map.value_size >= (1 << (KMALLOC_SHIFT_MAX - 1)) -
+	if (htab->map.value_size >= KMALLOC_MAX_SIZE -
 	    MAX_BPF_STACK - sizeof(struct htab_elem))
 		/* if value_size is bigger, the user space won't be able to
 		 * access the elements via bpf syscall. This check also makes
@@ -227,38 +339,37 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 		goto free_htab;
 
 	err = -ENOMEM;
-	htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct bucket),
-				      GFP_USER | __GFP_NOWARN);
-
-	if (!htab->buckets) {
-		htab->buckets = vmalloc(htab->n_buckets * sizeof(struct bucket));
-		if (!htab->buckets)
-			goto free_htab;
-	}
+	htab->buckets = bpf_map_area_alloc(htab->n_buckets *
+					   sizeof(struct bucket));
+	if (!htab->buckets)
+		goto free_htab;
 
 	for (i = 0; i < htab->n_buckets; i++) {
-		INIT_HLIST_HEAD(&htab->buckets[i].head);
+		INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
 		raw_spin_lock_init(&htab->buckets[i].lock);
 	}
 
-	if (!percpu) {
-		err = alloc_extra_elems(htab);
+	if (prealloc) {
+		err = prealloc_init(htab);
 		if (err)
 			goto free_buckets;
-	}
 
-	if (!(attr->map_flags & BPF_F_NO_PREALLOC)) {
-		err = prealloc_elems_and_freelist(htab);
-		if (err)
-			goto free_extra_elems;
+		if (!percpu && !lru) {
+			/* lru itself can remove the least used element, so
+			 * there is no need for an extra elem during map_update.
+			 */
+			err = alloc_extra_elems(htab);
+			if (err)
+				goto free_prealloc;
+		}
 	}
 
 	return &htab->map;
 
-free_extra_elems:
-	free_percpu(htab->extra_elems);
+free_prealloc:
+	prealloc_destroy(htab);
 free_buckets:
-	kvfree(htab->buckets);
+	bpf_map_area_free(htab->buckets);
 free_htab:
 	kfree(htab);
 	return ERR_PTR(err);
@@ -274,28 +385,52 @@ static inline struct bucket *__select_bucket(struct bpf_htab *htab, u32 hash)
 	return &htab->buckets[hash & (htab->n_buckets - 1)];
 }
 
-static inline struct hlist_head *select_bucket(struct bpf_htab *htab, u32 hash)
+static inline struct hlist_nulls_head *select_bucket(struct bpf_htab *htab, u32 hash)
 {
 	return &__select_bucket(htab, hash)->head;
 }
 
-static struct htab_elem *lookup_elem_raw(struct hlist_head *head, u32 hash,
+/* this lookup function can only be called with bucket lock taken */
+static struct htab_elem *lookup_elem_raw(struct hlist_nulls_head *head, u32 hash,
 					 void *key, u32 key_size)
 {
+	struct hlist_nulls_node *n;
 	struct htab_elem *l;
 
-	hlist_for_each_entry_rcu(l, head, hash_node)
+	hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
 		if (l->hash == hash && !memcmp(&l->key, key, key_size))
 			return l;
 
 	return NULL;
 }
 
+/* can be called without bucket lock. it will repeat the loop in
+ * the unlikely event when elements moved from one bucket into another
+ * while link list is being walked
+ */
+static struct htab_elem *lookup_nulls_elem_raw(struct hlist_nulls_head *head,
+					       u32 hash, void *key,
+					       u32 key_size, u32 n_buckets)
+{
+	struct hlist_nulls_node *n;
+	struct htab_elem *l;
+
+again:
+	hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
+		if (l->hash == hash && !memcmp(&l->key, key, key_size))
+			return l;
+
+	if (unlikely(get_nulls_value(n) != (hash & (n_buckets - 1))))
+		goto again;
+
+	return NULL;
+}
+
 /* Called from syscall or from eBPF program */
 static void *__htab_map_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
-	struct hlist_head *head;
+	struct hlist_nulls_head *head;
 	struct htab_elem *l;
 	u32 hash, key_size;
 
@@ -308,7 +443,7 @@ static void *__htab_map_lookup_elem(struct bpf_map *map, void *key)
 
 	head = select_bucket(htab, hash);
 
-	l = lookup_elem_raw(head, hash, key, key_size);
+	l = lookup_nulls_elem_raw(head, hash, key, key_size, htab->n_buckets);
 
 	return l;
 }
@@ -323,11 +458,52 @@ static void *htab_map_lookup_elem(struct bpf_map *map, void *key)
 	return NULL;
 }
 
+static void *htab_lru_map_lookup_elem(struct bpf_map *map, void *key)
+{
+	struct htab_elem *l = __htab_map_lookup_elem(map, key);
+
+	if (l) {
+		bpf_lru_node_set_ref(&l->lru_node);
+		return l->key + round_up(map->key_size, 8);
+	}
+
+	return NULL;
+}
+
+/* It is called from the bpf_lru_list when the LRU needs to delete
+ * older elements from the htab.
+ */
+static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
+{
+	struct bpf_htab *htab = (struct bpf_htab *)arg;
+	struct htab_elem *l = NULL, *tgt_l;
+	struct hlist_nulls_head *head;
+	struct hlist_nulls_node *n;
+	unsigned long flags;
+	struct bucket *b;
+
+	tgt_l = container_of(node, struct htab_elem, lru_node);
+	b = __select_bucket(htab, tgt_l->hash);
+	head = &b->head;
+
+	raw_spin_lock_irqsave(&b->lock, flags);
+
+	hlist_nulls_for_each_entry_rcu(l, n, head, hash_node)
+		if (l == tgt_l) {
+			hlist_nulls_del_rcu(&l->hash_node);
+			break;
+		}
+
+	raw_spin_unlock_irqrestore(&b->lock, flags);
+
+	return l == tgt_l;
+}
+
 /* Called from syscall */
 static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
-	struct hlist_head *head;
+	struct hlist_nulls_head *head;
 	struct htab_elem *l, *next_l;
 	u32 hash, key_size;
 	int i;
@@ -341,7 +517,7 @@ static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 	head = select_bucket(htab, hash);
 
 	/* lookup the key */
-	l = lookup_elem_raw(head, hash, key, key_size);
+	l = lookup_nulls_elem_raw(head, hash, key, key_size, htab->n_buckets);
 
 	if (!l) {
 		i = 0;
@@ -349,7 +525,7 @@ static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 	}
 
 	/* key was found, get next key in the same bucket */
-	next_l = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(&l->hash_node)),
+	next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_next_rcu(&l->hash_node)),
 				  struct htab_elem, hash_node);
 
 	if (next_l) {
@@ -368,7 +544,7 @@ find_first_elem:
 		head = select_bucket(htab, i);
 
 		/* pick first element in the bucket */
-		next_l = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(head)),
+		next_l = hlist_nulls_entry_safe(rcu_dereference_raw(hlist_nulls_first_rcu(head)),
 					  struct htab_elem, hash_node);
 		if (next_l) {
 			/* if it's not empty, just return it */
@@ -406,12 +582,7 @@ static void htab_elem_free_rcu(struct rcu_head *head)
 
 static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
 {
-	if (l->state == HTAB_EXTRA_ELEM_USED) {
-		l->state = HTAB_EXTRA_ELEM_FREE;
-		return;
-	}
-
-	if (!(htab->map.map_flags & BPF_F_NO_PREALLOC)) {
+	if (htab_is_prealloc(htab)) {
 		pcpu_freelist_push(&htab->freelist, &l->fnode);
 	} else {
 		atomic_dec(&htab->count);
@@ -420,46 +591,64 @@ static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
 	}
 }
 
+static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
+			    void *value, bool onallcpus)
+{
+	if (!onallcpus) {
+		/* copy true value_size bytes */
+		memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
+	} else {
+		u32 size = round_up(htab->map.value_size, 8);
+		int off = 0, cpu;
+
+		for_each_possible_cpu(cpu) {
+			bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
+					value + off, size);
+			off += size;
+		}
+	}
+}
+
 static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 					 void *value, u32 key_size, u32 hash,
 					 bool percpu, bool onallcpus,
-					 bool old_elem_exists)
+					 struct htab_elem *old_elem)
 {
 	u32 size = htab->map.value_size;
-	bool prealloc = !(htab->map.map_flags & BPF_F_NO_PREALLOC);
-	struct htab_elem *l_new;
+	bool prealloc = htab_is_prealloc(htab);
+	struct htab_elem *l_new, **pl_new;
 	void __percpu *pptr;
-	int err = 0;
 
 	if (prealloc) {
-		l_new = (struct htab_elem *)pcpu_freelist_pop(&htab->freelist);
-		if (!l_new)
-			err = -E2BIG;
-	} else {
-		if (atomic_inc_return(&htab->count) > htab->map.max_entries) {
-			atomic_dec(&htab->count);
-			err = -E2BIG;
+		if (old_elem) {
+			/* if we're updating the existing element,
+			 * use per-cpu extra elems to avoid freelist_pop/push
+			 */
+			pl_new = this_cpu_ptr(htab->extra_elems);
+			l_new = *pl_new;
+			*pl_new = old_elem;
 		} else {
-			l_new = kmalloc(htab->elem_size,
-					GFP_ATOMIC | __GFP_NOWARN);
-			if (!l_new)
-				return ERR_PTR(-ENOMEM);
-		}
-	}
+			struct pcpu_freelist_node *l;
 
-	if (err) {
-		if (!old_elem_exists)
-			return ERR_PTR(err);
-
-		/* if we're updating the existing element and the hash table
-		 * is full, use per-cpu extra elems
-		 */
-		l_new = this_cpu_ptr(htab->extra_elems);
-		if (l_new->state != HTAB_EXTRA_ELEM_FREE)
-			return ERR_PTR(-E2BIG);
-		l_new->state = HTAB_EXTRA_ELEM_USED;
+			l = pcpu_freelist_pop(&htab->freelist);
+			if (!l)
+				return ERR_PTR(-E2BIG);
+			l_new = container_of(l, struct htab_elem, fnode);
+		}
 	} else {
-		l_new->state = HTAB_NOT_AN_EXTRA_ELEM;
+		if (atomic_inc_return(&htab->count) > htab->map.max_entries)
+			if (!old_elem) {
+				/* when map is full and update() is replacing
+				 * old element, it's ok to allocate, since
+				 * old element will be freed immediately.
+				 * Otherwise return an error
+				 */
+				atomic_dec(&htab->count);
+				return ERR_PTR(-E2BIG);
+			}
+		l_new = kmalloc(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN);
+		if (!l_new)
+			return ERR_PTR(-ENOMEM);
 	}
 
 	memcpy(l_new->key, key, key_size);
@@ -479,18 +668,8 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 			}
 		}
 
-		if (!onallcpus) {
-			/* copy true value_size bytes */
-			memcpy(this_cpu_ptr(pptr), value, htab->map.value_size);
-		} else {
-			int off = 0, cpu;
+		pcpu_copy_value(htab, pptr, value, onallcpus);
 
-			for_each_possible_cpu(cpu) {
-				bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
-						value + off, size);
-				off += size;
-			}
-		}
 		if (!prealloc)
 			htab_elem_set_ptr(l_new, key_size, pptr);
 	} else {
@@ -521,7 +700,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 	struct htab_elem *l_new = NULL, *l_old;
-	struct hlist_head *head;
+	struct hlist_nulls_head *head;
 	unsigned long flags;
 	struct bucket *b;
 	u32 key_size, hash;
@@ -550,7 +729,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 		goto err;
 
 	l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false,
-				!!l_old);
+				l_old);
 	if (IS_ERR(l_new)) {
 		/* all pre-allocated elements are in use or memory exhausted */
 		ret = PTR_ERR(l_new);
@@ -560,10 +739,11 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	/* add new element to the head of the list, so that
 	 * concurrent search will find it before old elem
 	 */
-	hlist_add_head_rcu(&l_new->hash_node, head);
+	hlist_nulls_add_head_rcu(&l_new->hash_node, head);
 	if (l_old) {
-		hlist_del_rcu(&l_old->hash_node);
-		free_htab_elem(htab, l_old);
+		hlist_nulls_del_rcu(&l_old->hash_node);
+		if (!htab_is_prealloc(htab))
+			free_htab_elem(htab, l_old);
 	}
 	ret = 0;
 err:
@@ -571,13 +751,77 @@ err:
 	return ret;
 }
 
+static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
+				    u64 map_flags)
+{
+	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
+	struct htab_elem *l_new, *l_old = NULL;
+	struct hlist_nulls_head *head;
+	unsigned long flags;
+	struct bucket *b;
+	u32 key_size, hash;
+	int ret;
+
+	if (unlikely(map_flags > BPF_EXIST))
+		/* unknown flags */
+		return -EINVAL;
+
+	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	key_size = map->key_size;
+
+	hash = htab_map_hash(key, key_size);
+
+	b = __select_bucket(htab, hash);
+	head = &b->head;
+
+	/* For LRU, we need to alloc before taking bucket's
+	 * spinlock because getting free nodes from LRU may need
+	 * to remove older elements from htab and this removal
+	 * operation will need a bucket lock.
+	 */
+	l_new = prealloc_lru_pop(htab, key, hash);
+	if (!l_new)
+		return -ENOMEM;
+	memcpy(l_new->key + round_up(map->key_size, 8), value, map->value_size);
+
+	/* bpf_map_update_elem() can be called in_irq() */
+	raw_spin_lock_irqsave(&b->lock, flags);
+
+	l_old = lookup_elem_raw(head, hash, key, key_size);
+
+	ret = check_flags(htab, l_old, map_flags);
+	if (ret)
+		goto err;
+
+	/* add new element to the head of the list, so that
+	 * concurrent search will find it before old elem
+	 */
+	hlist_nulls_add_head_rcu(&l_new->hash_node, head);
+	if (l_old) {
+		bpf_lru_node_set_ref(&l_new->lru_node);
+		hlist_nulls_del_rcu(&l_old->hash_node);
+	}
+	ret = 0;
+
+err:
+	raw_spin_unlock_irqrestore(&b->lock, flags);
+
+	if (ret)
+		bpf_lru_push_free(&htab->lru, &l_new->lru_node);
+	else if (l_old)
+		bpf_lru_push_free(&htab->lru, &l_old->lru_node);
+
+	return ret;
+}
+
 static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
 					 void *value, u64 map_flags,
 					 bool onallcpus)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 	struct htab_elem *l_new = NULL, *l_old;
-	struct hlist_head *head;
+	struct hlist_nulls_head *head;
 	unsigned long flags;
 	struct bucket *b;
 	u32 key_size, hash;
@@ -606,34 +850,86 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
 		goto err;
 
 	if (l_old) {
-		void __percpu *pptr = htab_elem_get_ptr(l_old, key_size);
-		u32 size = htab->map.value_size;
-
 		/* per-cpu hash map can update value in-place */
-		if (!onallcpus) {
-			memcpy(this_cpu_ptr(pptr), value, size);
-		} else {
-			int off = 0, cpu;
-
-			size = round_up(size, 8);
-			for_each_possible_cpu(cpu) {
-				bpf_long_memcpy(per_cpu_ptr(pptr, cpu),
-						value + off, size);
-				off += size;
-			}
-		}
+		pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
+				value, onallcpus);
 	} else {
 		l_new = alloc_htab_elem(htab, key, value, key_size,
-					hash, true, onallcpus, false);
+					hash, true, onallcpus, NULL);
 		if (IS_ERR(l_new)) {
 			ret = PTR_ERR(l_new);
 			goto err;
 		}
-		hlist_add_head_rcu(&l_new->hash_node, head);
+		hlist_nulls_add_head_rcu(&l_new->hash_node, head);
+	}
+	ret = 0;
+err:
+	raw_spin_unlock_irqrestore(&b->lock, flags);
+	return ret;
+}
+
+static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
+					     void *value, u64 map_flags,
+					     bool onallcpus)
+{
+	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
+	struct htab_elem *l_new = NULL, *l_old;
+	struct hlist_nulls_head *head;
+	unsigned long flags;
+	struct bucket *b;
+	u32 key_size, hash;
+	int ret;
+
+	if (unlikely(map_flags > BPF_EXIST))
+		/* unknown flags */
+		return -EINVAL;
+
+	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	key_size = map->key_size;
+
+	hash = htab_map_hash(key, key_size);
+
+	b = __select_bucket(htab, hash);
+	head = &b->head;
+
+	/* For LRU, we need to alloc before taking bucket's
+	 * spinlock because LRU's elem alloc may need
+	 * to remove older elem from htab and this removal
+	 * operation will need a bucket lock.
+	 */
+	if (map_flags != BPF_EXIST) {
+		l_new = prealloc_lru_pop(htab, key, hash);
+		if (!l_new)
+			return -ENOMEM;
+	}
+
+	/* bpf_map_update_elem() can be called in_irq() */
+	raw_spin_lock_irqsave(&b->lock, flags);
+
+	l_old = lookup_elem_raw(head, hash, key, key_size);
+
+	ret = check_flags(htab, l_old, map_flags);
+	if (ret)
+		goto err;
+
+	if (l_old) {
+		bpf_lru_node_set_ref(&l_old->lru_node);
+
+		/* per-cpu hash map can update value in-place */
+		pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
+				value, onallcpus);
+	} else {
+		pcpu_copy_value(htab, htab_elem_get_ptr(l_new, key_size),
+				value, onallcpus);
+		hlist_nulls_add_head_rcu(&l_new->hash_node, head);
+		l_new = NULL;
 	}
 	ret = 0;
 err:
 	raw_spin_unlock_irqrestore(&b->lock, flags);
+	if (l_new)
+		bpf_lru_push_free(&htab->lru, &l_new->lru_node);
 	return ret;
 }
 
@@ -643,11 +939,18 @@ static int htab_percpu_map_update_elem(struct bpf_map *map, void *key,
 	return __htab_percpu_map_update_elem(map, key, value, map_flags, false);
 }
 
+static int htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
+					   void *value, u64 map_flags)
+{
+	return __htab_lru_percpu_map_update_elem(map, key, value, map_flags,
+						 false);
+}
+
 /* Called from syscall or from eBPF program */
 static int htab_map_delete_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
-	struct hlist_head *head;
+	struct hlist_nulls_head *head;
 	struct bucket *b;
 	struct htab_elem *l;
 	unsigned long flags;
@@ -667,7 +970,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
 	l = lookup_elem_raw(head, hash, key, key_size);
 
 	if (l) {
-		hlist_del_rcu(&l->hash_node);
+		hlist_nulls_del_rcu(&l->hash_node);
 		free_htab_elem(htab, l);
 		ret = 0;
 	}
@@ -676,19 +979,51 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
 	return ret;
 }
 
+static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
+{
+	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
+	struct hlist_nulls_head *head;
+	struct bucket *b;
+	struct htab_elem *l;
+	unsigned long flags;
+	u32 hash, key_size;
+	int ret = -ENOENT;
+
+	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	key_size = map->key_size;
+
+	hash = htab_map_hash(key, key_size);
+	b = __select_bucket(htab, hash);
+	head = &b->head;
+
+	raw_spin_lock_irqsave(&b->lock, flags);
+
+	l = lookup_elem_raw(head, hash, key, key_size);
+
+	if (l) {
+		hlist_nulls_del_rcu(&l->hash_node);
+		ret = 0;
+	}
+
+	raw_spin_unlock_irqrestore(&b->lock, flags);
+	if (l)
+		bpf_lru_push_free(&htab->lru, &l->lru_node);
+	return ret;
+}
+
 static void delete_all_elements(struct bpf_htab *htab)
 {
 	int i;
 
 	for (i = 0; i < htab->n_buckets; i++) {
-		struct hlist_head *head = select_bucket(htab, i);
-		struct hlist_node *n;
+		struct hlist_nulls_head *head = select_bucket(htab, i);
+		struct hlist_nulls_node *n;
 		struct htab_elem *l;
 
-		hlist_for_each_entry_safe(l, n, head, hash_node) {
-			hlist_del_rcu(&l->hash_node);
-			if (l->state != HTAB_EXTRA_ELEM_USED)
-				htab_elem_free(htab, l);
+		hlist_nulls_for_each_entry_safe(l, n, head, hash_node) {
+			hlist_nulls_del_rcu(&l->hash_node);
+			htab_elem_free(htab, l);
 		}
 	}
 }
@@ -708,14 +1043,13 @@ static void htab_map_free(struct bpf_map *map)
 	 * not have executed. Wait for them.
 	 */
 	rcu_barrier();
-	if (htab->map.map_flags & BPF_F_NO_PREALLOC) {
+	if (!htab_is_prealloc(htab))
 		delete_all_elements(htab);
-	} else {
-		htab_free_elems(htab);
-		pcpu_freelist_destroy(&htab->freelist);
-	}
+	else
+		prealloc_destroy(htab);
+
 	free_percpu(htab->extra_elems);
-	kvfree(htab->buckets);
+	bpf_map_area_free(htab->buckets);
 	kfree(htab);
 }
 
@@ -728,11 +1062,25 @@ static const struct bpf_map_ops htab_ops = {
 	.map_delete_elem = htab_map_delete_elem,
 };
 
-static struct bpf_map_type_list htab_type __read_mostly = {
+static struct bpf_map_type_list htab_type __ro_after_init = {
 	.ops = &htab_ops,
 	.type = BPF_MAP_TYPE_HASH,
 };
 
+static const struct bpf_map_ops htab_lru_ops = {
+	.map_alloc = htab_map_alloc,
+	.map_free = htab_map_free,
+	.map_get_next_key = htab_map_get_next_key,
+	.map_lookup_elem = htab_lru_map_lookup_elem,
+	.map_update_elem = htab_lru_map_update_elem,
+	.map_delete_elem = htab_lru_map_delete_elem,
+};
+
+static struct bpf_map_type_list htab_lru_type __ro_after_init = {
+	.ops = &htab_lru_ops,
+	.type = BPF_MAP_TYPE_LRU_HASH,
+};
+
 /* Called from eBPF program */
 static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
 {
@@ -744,8 +1092,21 @@ static void *htab_percpu_map_lookup_elem(struct bpf_map *map, void *key)
 		return NULL;
 }
 
+static void *htab_lru_percpu_map_lookup_elem(struct bpf_map *map, void *key)
+{
+	struct htab_elem *l = __htab_map_lookup_elem(map, key);
+
+	if (l) {
+		bpf_lru_node_set_ref(&l->lru_node);
+		return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
+	}
+
+	return NULL;
+}
+
 int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
 {
+	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 	struct htab_elem *l;
 	void __percpu *pptr;
 	int ret = -ENOENT;
@@ -761,6 +1122,8 @@ int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
 	l = __htab_map_lookup_elem(map, key);
 	if (!l)
 		goto out;
+	if (htab_is_lru(htab))
+		bpf_lru_node_set_ref(&l->lru_node);
 	pptr = htab_elem_get_ptr(l, map->key_size);
 	for_each_possible_cpu(cpu) {
 		bpf_long_memcpy(value + off,
@@ -776,10 +1139,16 @@ out:
 int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
 			   u64 map_flags)
 {
+	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 	int ret;
 
 	rcu_read_lock();
-	ret = __htab_percpu_map_update_elem(map, key, value, map_flags, true);
+	if (htab_is_lru(htab))
+		ret = __htab_lru_percpu_map_update_elem(map, key, value,
+							map_flags, true);
+	else
+		ret = __htab_percpu_map_update_elem(map, key, value, map_flags,
+						    true);
 	rcu_read_unlock();
 
 	return ret;
@@ -794,15 +1163,31 @@ static const struct bpf_map_ops htab_percpu_ops = {
 	.map_delete_elem = htab_map_delete_elem,
 };
 
-static struct bpf_map_type_list htab_percpu_type __read_mostly = {
+static struct bpf_map_type_list htab_percpu_type __ro_after_init = {
 	.ops = &htab_percpu_ops,
 	.type = BPF_MAP_TYPE_PERCPU_HASH,
 };
 
+static const struct bpf_map_ops htab_lru_percpu_ops = {
+	.map_alloc = htab_map_alloc,
+	.map_free = htab_map_free,
+	.map_get_next_key = htab_map_get_next_key,
+	.map_lookup_elem = htab_lru_percpu_map_lookup_elem,
+	.map_update_elem = htab_lru_percpu_map_update_elem,
+	.map_delete_elem = htab_lru_map_delete_elem,
+};
+
+static struct bpf_map_type_list htab_lru_percpu_type __ro_after_init = {
+	.ops = &htab_lru_percpu_ops,
+	.type = BPF_MAP_TYPE_LRU_PERCPU_HASH,
+};
+
 static int __init register_htab_map(void)
 {
 	bpf_register_map_type(&htab_type);
 	bpf_register_map_type(&htab_percpu_type);
+	bpf_register_map_type(&htab_lru_type);
+	bpf_register_map_type(&htab_lru_percpu_type);
 	return 0;
 }
 late_initcall(register_htab_map);