From patchwork Sun May 1 17:38:14 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dai Ngo X-Patchwork-Id: 12833707 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2FD9C433F5 for ; Sun, 1 May 2022 17:38:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353551AbiEARl7 (ORCPT ); Sun, 1 May 2022 13:41:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39216 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353457AbiEARlv (ORCPT ); Sun, 1 May 2022 13:41:51 -0400 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B689BDB6; Sun, 1 May 2022 10:38:25 -0700 (PDT) Received: from pps.filterd (m0246629.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 2418N8ep032436; Sun, 1 May 2022 17:38:23 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references; s=corp-2021-07-09; bh=mKSDOa4qRzjE/NpQsELIZA2a0Z8+WDa1MO8RxPDFNxg=; b=w1gbt52OwNMv/hlk+YXoJYXcfhfep/y9vMeViBC2fZn4uTKGZWBOr4oYeYXpdbeVSKse Di2nsT9HTA3Is21TfIjlAMES+BFEC0cz0rON6p3dmosMLzzDdP7KAYYOUrjq73NaIPAx Vpgx5Fr8nQVZw9e8jlGJFDf78mOB6nuDCPY90OiIvAGNLJTZTAlr3AsbpkqFbsocMAol 9620/3Juas1BZZoqMzrur+k4jeOxAHb1WY+FlcAibHulV1rLTCCjuuzqYiTfgDCzwNbA 2VQCymbg+PwGBFk4R9LESwJhrqprTEbifK+hI5N7R79wk/hCQewem/gzwHse4aWhTvsx oQ== Received: from phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta02.appoci.oracle.com [147.154.114.232]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3frw0aht9p-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sun, 01 May 2022 17:38:23 +0000 Received: from pps.filterd (phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (8.16.1.2/8.16.1.2) with SMTP id 241HZDwr033356; Sun, 1 May 2022 17:38:22 GMT Received: from pps.reinject (localhost [127.0.0.1]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com with ESMTP id 3fs1a37w6n-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sun, 01 May 2022 17:38:22 +0000 Received: from phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 241HauVj034841; Sun, 1 May 2022 17:38:22 GMT Received: from ca-common-hq.us.oracle.com (ca-common-hq.us.oracle.com [10.211.9.209]) by phxpaimrmta02.imrmtpd1.prodappphxaev1.oraclevcn.com with ESMTP id 3fs1a37w5x-6; Sun, 01 May 2022 17:38:22 +0000 From: Dai Ngo To: chuck.lever@oracle.com, bfields@fieldses.org Cc: jlayton@redhat.com, viro@zeniv.linux.org.uk, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH RFC v24 5/7] fs/lock: add 2 callbacks to lock_manager_operations to resolve conflict Date: Sun, 1 May 2022 10:38:14 -0700 Message-Id: <1651426696-15509-6-git-send-email-dai.ngo@oracle.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1651426696-15509-1-git-send-email-dai.ngo@oracle.com> References: <1651426696-15509-1-git-send-email-dai.ngo@oracle.com> X-Proofpoint-GUID: VA4Ga4N708Q_vhDjWd26Jx9SCIQaHcjG X-Proofpoint-ORIG-GUID: VA4Ga4N708Q_vhDjWd26Jx9SCIQaHcjG Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add 2 new callbacks, lm_lock_expirable and lm_expire_lock, to lock_manager_operations to allow the lock manager to take appropriate action to resolve the lock conflict if possible. A new field, lm_mod_owner, is also added to lock_manager_operations. The lm_mod_owner is used by the fs/lock code to make sure the lock manager module such as nfsd, is not freed while lock conflict is being resolved. lm_lock_expirable checks and returns true to indicate that the lock conflict can be resolved else return false. This callback must be called with the flc_lock held so it can not block. lm_expire_lock is called to resolve the lock conflict if the returned value from lm_lock_expirable is true. This callback is called without the flc_lock held since it's allowed to block. Upon returning from this callback, the lock conflict should be resolved and the caller is expected to restart the conflict check from the beginnning of the list. Lock manager, such as NFSv4 courteous server, uses this callback to resolve conflict by destroying lock owner, or the NFSv4 courtesy client (client that has expired but allowed to maintains its states) that owns the lock. Signed-off-by: Dai Ngo Reviewed-by: J. Bruce Fields --- Documentation/filesystems/locking.rst | 4 ++++ fs/locks.c | 45 ++++++++++++++++++++++++++++++++--- include/linux/fs.h | 3 +++ 3 files changed, 49 insertions(+), 3 deletions(-) diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index c26d854275a0..0997a258361a 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -428,6 +428,8 @@ prototypes:: void (*lm_break)(struct file_lock *); /* break_lease callback */ int (*lm_change)(struct file_lock **, int); bool (*lm_breaker_owns_lease)(struct file_lock *); + bool (*lm_lock_expirable)(struct file_lock *); + void (*lm_expire_lock)(void); locking rules: @@ -439,6 +441,8 @@ lm_grant: no no no lm_break: yes no no lm_change yes no no lm_breaker_owns_lease: yes no no +lm_lock_expirable yes no no +lm_expire_lock no no yes ====================== ============= ================= ========= buffer_head diff --git a/fs/locks.c b/fs/locks.c index c369841ef7d1..17917da06463 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -902,6 +902,9 @@ posix_test_lock(struct file *filp, struct file_lock *fl) struct file_lock *cfl; struct file_lock_context *ctx; struct inode *inode = locks_inode(filp); + void *owner; + bool ret; + void (*func)(void); ctx = smp_load_acquire(&inode->i_flctx); if (!ctx || list_empty_careful(&ctx->flc_posix)) { @@ -909,12 +912,28 @@ posix_test_lock(struct file *filp, struct file_lock *fl) return; } +retry: spin_lock(&ctx->flc_lock); list_for_each_entry(cfl, &ctx->flc_posix, fl_list) { - if (posix_locks_conflict(fl, cfl)) { - locks_copy_conflock(fl, cfl); - goto out; + if (!posix_locks_conflict(fl, cfl)) + continue; + if (cfl->fl_lmops && cfl->fl_lmops->lm_mod_owner && + cfl->fl_lmops->lm_lock_expirable && + cfl->fl_lmops->lm_expire_lock) { + ret = (*cfl->fl_lmops->lm_lock_expirable)(cfl); + if (!ret) + goto conflict; + owner = cfl->fl_lmops->lm_mod_owner; + func = cfl->fl_lmops->lm_expire_lock; + __module_get(owner); + spin_unlock(&ctx->flc_lock); + (*func)(); + module_put(owner); + goto retry; } +conflict: + locks_copy_conflock(fl, cfl); + goto out; } fl->fl_type = F_UNLCK; out: @@ -1088,6 +1107,9 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, int error; bool added = false; LIST_HEAD(dispose); + void *owner; + bool ret; + void (*func)(void); ctx = locks_get_lock_context(inode, request->fl_type); if (!ctx) @@ -1106,6 +1128,7 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, new_fl2 = locks_alloc_lock(); } +retry: percpu_down_read(&file_rwsem); spin_lock(&ctx->flc_lock); /* @@ -1117,6 +1140,22 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, list_for_each_entry(fl, &ctx->flc_posix, fl_list) { if (!posix_locks_conflict(request, fl)) continue; + if (fl->fl_lmops && fl->fl_lmops->lm_mod_owner && + fl->fl_lmops->lm_lock_expirable && + fl->fl_lmops->lm_expire_lock) { + ret = (*fl->fl_lmops->lm_lock_expirable)(fl); + if (!ret) + goto conflict; + owner = fl->fl_lmops->lm_mod_owner; + func = fl->fl_lmops->lm_expire_lock; + __module_get(owner); + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + (*func)(); + module_put(owner); + goto retry; + } +conflict: if (conflock) locks_copy_conflock(conflock, fl); error = -EAGAIN; diff --git a/include/linux/fs.h b/include/linux/fs.h index b8ed7f974fb4..aa6c1bbdb8c4 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1029,6 +1029,7 @@ struct file_lock_operations { }; struct lock_manager_operations { + void *lm_mod_owner; fl_owner_t (*lm_get_owner)(fl_owner_t); void (*lm_put_owner)(fl_owner_t); void (*lm_notify)(struct file_lock *); /* unblock callback */ @@ -1037,6 +1038,8 @@ struct lock_manager_operations { int (*lm_change)(struct file_lock *, int, struct list_head *); void (*lm_setup)(struct file_lock *, void **); bool (*lm_breaker_owns_lease)(struct file_lock *); + bool (*lm_lock_expirable)(struct file_lock *cfl); + void (*lm_expire_lock)(void); }; struct lock_manager {