From patchwork Sat Jun 1 03:07:33 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 2646831 Return-Path: X-Original-To: patchwork-linux-nfs@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork1.kernel.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by patchwork1.kernel.org (Postfix) with ESMTP id 6135A3FD4E for ; Sat, 1 Jun 2013 03:11:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753102Ab3FADIx (ORCPT ); Fri, 31 May 2013 23:08:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:25967 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757971Ab3FADIR (ORCPT ); Fri, 31 May 2013 23:08:17 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r5137mJL001455 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 31 May 2013 23:07:48 -0400 Received: from sikun.lab.eng.rdu2.redhat.com (sikun.lab.eng.rdu2.redhat.com [10.8.0.43]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id r5137YWg001118; Fri, 31 May 2013 23:07:47 -0400 From: Jeff Layton To: viro@zeniv.linux.org.uk, matthew@wil.cx, bfields@fieldses.org Cc: dhowells@redhat.com, sage@inktank.com, smfrench@gmail.com, swhiteho@redhat.com, Trond.Myklebust@netapp.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-afs@lists.infradead.org, ceph-devel@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, cluster-devel@redhat.com, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, piastryyy@gmail.com Subject: [PATCH v1 10/11] locks: add a new "lm_owner_key" lock operation Date: Fri, 31 May 2013 23:07:33 -0400 Message-Id: <1370056054-25449-11-git-send-email-jlayton@redhat.com> In-Reply-To: <1370056054-25449-1-git-send-email-jlayton@redhat.com> References: <1370056054-25449-1-git-send-email-jlayton@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org Currently, the hashing that the locking code uses to add these values to the blocked_hash is simply calculated using fl_owner field. That's valid in most cases except for server-side lockd, which validates the owner of a lock based on fl_owner and fl_pid. In the case where you have a small number of NFS clients doing a lot of locking between different processes, you could end up with all the blocked requests sitting in a very small number of hash buckets. Add a new lm_owner_key operation to the lock_manager_operations that will generate an unsigned long to use as the key in the hashtable. That function is only implemented for server-side lockd, and simply XORs the fl_owner and fl_pid. Signed-off-by: Jeff Layton --- Documentation/filesystems/Locking | 18 +++++++++++------- fs/lockd/svclock.c | 12 ++++++++++++ fs/locks.c | 13 ++++++++++--- include/linux/fs.h | 1 + 4 files changed, 34 insertions(+), 10 deletions(-) diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index 13f91ab..ee351ac 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -351,6 +351,7 @@ fl_release_private: maybe no ----------------------- lock_manager_operations --------------------------- prototypes: int (*lm_compare_owner)(struct file_lock *, struct file_lock *); + unsigned long (*lm_owner_key)(struct file_lock *); void (*lm_notify)(struct file_lock *); /* unblock callback */ int (*lm_grant)(struct file_lock *, struct file_lock *, int); void (*lm_break)(struct file_lock *); /* break_lease callback */ @@ -360,18 +361,21 @@ locking rules: inode->i_lock file_lock_lock may block lm_compare_owner: yes maybe no +lm_owner_key yes yes no lm_notify: yes no no lm_grant: no no no lm_break: yes no no lm_change yes no no - ->lm_compare_owner is generally called with *an* inode->i_lock -held. It may not be the i_lock of the inode for either file_lock being -compared! This is the case with deadlock detection, since the code has -to chase down the owners of locks that may be entirely unrelated to the -one on which the lock is being acquired. For deadlock detection however, -the file_lock_lock is also held. The locks primarily ensure that neither -file_lock disappear out from under you while doing the comparison. + ->lm_compare_owner and ->lm_owner_key are generally called with +*an* inode->i_lock held. It may not be the i_lock of the inode +associated with either file_lock argument! This is the case with deadlock +detection, since the code has to chase down the owners of locks that may +be entirely unrelated to the one on which the lock is being acquired. +For deadlock detection however, the file_lock_lock is also held. The +fact that these locks are held ensures that the file_locks do not +disappear out from under you while doing the comparison or generating an +owner key. --------------------------- buffer_head ----------------------------------- prototypes: diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c index e703318..ce2cdab 100644 --- a/fs/lockd/svclock.c +++ b/fs/lockd/svclock.c @@ -744,8 +744,20 @@ static int nlmsvc_same_owner(struct file_lock *fl1, struct file_lock *fl2) return fl1->fl_owner == fl2->fl_owner && fl1->fl_pid == fl2->fl_pid; } +/* + * Since NLM uses two "keys" for tracking locks, we need to hash them down + * to one for the blocked_hash. Here, we're just xor'ing the host address + * with the pid in order to create a key value for picking a hash bucket. + */ +static unsigned long +nlmsvc_owner_key(struct file_lock *fl) +{ + return (unsigned long)fl->fl_owner ^ (unsigned long)fl->fl_pid; +} + const struct lock_manager_operations nlmsvc_lock_operations = { .lm_compare_owner = nlmsvc_same_owner, + .lm_owner_key = nlmsvc_owner_key, .lm_notify = nlmsvc_notify_blocked, .lm_grant = nlmsvc_grant_deferred, }; diff --git a/fs/locks.c b/fs/locks.c index 0d030ce..8219187 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -491,13 +491,20 @@ static int posix_same_owner(struct file_lock *fl1, struct file_lock *fl2) return fl1->fl_owner == fl2->fl_owner; } +static unsigned long +posix_owner_key(struct file_lock *fl) +{ + if (fl->fl_lmops && fl->fl_lmops->lm_owner_key) + return fl->fl_lmops->lm_owner_key(fl); + return (unsigned long)fl->fl_owner; +} + /* Remove a blocker or lock from one of the global lists */ static inline void locks_insert_global_blocked(struct file_lock *waiter) { spin_lock(&file_lock_lock); - hash_add(blocked_hash, &waiter->fl_link, - (unsigned long)waiter->fl_owner); + hash_add(blocked_hash, &waiter->fl_link, posix_owner_key(waiter)); spin_unlock(&file_lock_lock); } @@ -716,7 +723,7 @@ static struct file_lock *what_owner_is_waiting_for(struct file_lock *block_fl) { struct file_lock *fl, *ret = NULL; - hash_for_each_possible(blocked_hash, fl, fl_link, (unsigned long)block_fl->fl_owner) { + hash_for_each_possible(blocked_hash, fl, fl_link, posix_owner_key(block_fl)) { if (posix_same_owner(fl, block_fl)) { ret = fl->fl_next; if (likely(ret)) diff --git a/include/linux/fs.h b/include/linux/fs.h index 07a009e..4906cf5 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -908,6 +908,7 @@ struct file_lock_operations { struct lock_manager_operations { int (*lm_compare_owner)(struct file_lock *, struct file_lock *); + unsigned long (*lm_owner_key)(struct file_lock *); void (*lm_notify)(struct file_lock *); /* unblock callback */ int (*lm_grant)(struct file_lock *, struct file_lock *, int); void (*lm_break)(struct file_lock *);