[RFC v2 2/7] user_ns: use new hashtable implementation

[Sasha Levin]

Switch user_ns to use the new hashtable implementation. This reduces the amount of
generic unrelated code in user_ns.

Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx>
---
 kernel/user.c |   53 ++++++++++++++++++-----------------------------------
 1 files changed, 18 insertions(+), 35 deletions(-)

diff --git a/kernel/user.c b/kernel/user.c
index b815fef..555c71a 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -16,6 +16,7 @@
 #include <linux/interrupt.h>
 #include <linux/export.h>
 #include <linux/user_namespace.h>
+#include <linux/hashtable.h>
 
 /*
  * userns count is 1 for root user, 1 for init_uts_ns,
@@ -50,15 +51,14 @@ EXPORT_SYMBOL_GPL(init_user_ns);
  * UID task count cache, to get fast user lookup in "alloc_uid"
  * when changing user ID's (ie setuid() and friends).
  */
-
-#define UIDHASH_BITS	(CONFIG_BASE_SMALL ? 3 : 7)
-#define UIDHASH_SZ	(1 << UIDHASH_BITS)
-#define UIDHASH_MASK		(UIDHASH_SZ - 1)
-#define __uidhashfn(uid)	(((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
-#define uidhashentry(uid)	(uidhash_table + __uidhashfn((__kuid_val(uid))))
+#define UIDHASH_BITS		(CONFIG_BASE_SMALL ? 3 : 7)
+#define UIDHASH_CMP(obj, key) 	((obj)->uid == (key))
+#define uidhash_entry(key)	(hash_get(&uidhash_table, key,		\
+				struct user_struct, uidhash_node,	\
+				UIDHASH_CMP))
 
 static struct kmem_cache *uid_cachep;
-struct hlist_head uidhash_table[UIDHASH_SZ];
+DEFINE_STATIC_HASHTABLE(uidhash_table, UIDHASH_BITS);
 
 /*
  * The uidhash_lock is mostly taken from process context, but it is
@@ -84,29 +84,14 @@ struct user_struct root_user = {
 /*
  * These routines must be called with the uidhash spinlock held!
  */
-static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
+static void uid_hash_insert(struct user_struct *up)
 {
-	hlist_add_head(&up->uidhash_node, hashent);
+	hash_add(&uidhash_table, &up->uidhash_node, up->uid);
 }
 
 static void uid_hash_remove(struct user_struct *up)
 {
-	hlist_del_init(&up->uidhash_node);
-}
-
-static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
-{
-	struct user_struct *user;
-	struct hlist_node *h;
-
-	hlist_for_each_entry(user, h, hashent, uidhash_node) {
-		if (uid_eq(user->uid, uid)) {
-			atomic_inc(&user->__count);
-			return user;
-		}
-	}
-
-	return NULL;
+	hash_del(&up->uidhash_node);
 }
 
 /* IRQs are disabled and uidhash_lock is held upon function entry.
@@ -135,7 +120,9 @@ struct user_struct *find_user(kuid_t uid)
 	unsigned long flags;
 
 	spin_lock_irqsave(&uidhash_lock, flags);
-	ret = uid_hash_find(uid, uidhashentry(uid));
+	ret = uidhash_entry(uid);
+	if (ret)
+		atomic_inc(&ret->__count);
 	spin_unlock_irqrestore(&uidhash_lock, flags);
 	return ret;
 }
@@ -156,11 +143,10 @@ void free_uid(struct user_struct *up)
 
 struct user_struct *alloc_uid(kuid_t uid)
 {
-	struct hlist_head *hashent = uidhashentry(uid);
 	struct user_struct *up, *new;
 
 	spin_lock_irq(&uidhash_lock);
-	up = uid_hash_find(uid, hashent);
+	up = uidhash_entry(uid);
 	spin_unlock_irq(&uidhash_lock);
 
 	if (!up) {
@@ -176,13 +162,13 @@ struct user_struct *alloc_uid(kuid_t uid)
 		 * on adding the same user already..
 		 */
 		spin_lock_irq(&uidhash_lock);
-		up = uid_hash_find(uid, hashent);
+		up = uidhash_entry(uid);
 		if (up) {
 			key_put(new->uid_keyring);
 			key_put(new->session_keyring);
 			kmem_cache_free(uid_cachep, new);
 		} else {
-			uid_hash_insert(new, hashent);
+			uid_hash_insert(new);
 			up = new;
 		}
 		spin_unlock_irq(&uidhash_lock);
@@ -196,17 +182,14 @@ out_unlock:
 
 static int __init uid_cache_init(void)
 {
-	int n;
-
 	uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
 			0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
 
-	for(n = 0; n < UIDHASH_SZ; ++n)
-		INIT_HLIST_HEAD(uidhash_table + n);
+	hash_init(&uidhash_table, UIDHASH_BITS);
 
 	/* Insert the root user immediately (init already runs as root) */
 	spin_lock_irq(&uidhash_lock);
-	uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
+	uid_hash_insert(&root_user);
 	spin_unlock_irq(&uidhash_lock);
 
 	return 0;
-- 
1.7.8.6

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