From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754129Ab2HEA65 (ORCPT ); Sat, 4 Aug 2012 20:58:57 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:56051 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753954Ab2HEA6w (ORCPT ); Sat, 4 Aug 2012 20:58:52 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Sasha Levin Cc: torvalds@linux-foundation.org, tj@kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, paul.gortmaker@windriver.com, davem@davemloft.net, rostedt@goodmis.org, mingo@elte.hu, aarcange@redhat.com, ericvh@gmail.com, netdev@vger.kernel.org References: <1344003788-1417-1-git-send-email-levinsasha928@gmail.com> <1344003788-1417-3-git-send-email-levinsasha928@gmail.com> Date: Sat, 04 Aug 2012 17:58:32 -0700 In-Reply-To: <1344003788-1417-3-git-send-email-levinsasha928@gmail.com> (Sasha Levin's message of "Fri, 3 Aug 2012 16:23:03 +0200") Message-ID: <87pq76tarr.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=;;;mid=;;;hst=in02.mta.xmission.com;;;ip=98.207.153.68;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1+bdFC9EB8n5pkoAxo8KHQYZ/edI2vwvq4= X-SA-Exim-Connect-IP: 98.207.153.68 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -3.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0063] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Sasha Levin X-Spam-Relay-Country: Subject: Re: [RFC v2 2/7] user_ns: use new hashtable implementation X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Fri, 06 Aug 2010 16:31:04 -0600) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sasha Levin writes: > Switch user_ns to use the new hashtable implementation. This reduces the amount of > generic unrelated code in user_ns. Just looking at this ick. - Your comparison function is broken. - The naming is awkward. hash_get without a reference count being incremented? - The magic is deep. hash_get is named like a function but takes a piece of code to call like only a macro can. - uid_hash_find always bumped the reference count but your uidhash_entry doesn't nor do all of the callers of uidhash_entry bump the reference count. Nacked-by: "Eric W. Biederman" I don't have the time for a new improved better hash table that makes the code buggier. Eric > Signed-off-by: Sasha Levin > --- > 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 > #include > #include > +#include > > /* > * 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;