From patchwork Thu Apr 28 07:06:33 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dai Ngo X-Patchwork-Id: 12830086 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 A9BE3C433EF for ; Thu, 28 Apr 2022 07:07:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231905AbiD1HK0 (ORCPT ); Thu, 28 Apr 2022 03:10:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36142 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244945AbiD1HKL (ORCPT ); Thu, 28 Apr 2022 03:10:11 -0400 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F04D69AE55; Thu, 28 Apr 2022 00:06:49 -0700 (PDT) Received: from pps.filterd (m0246617.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 23S76bLI025802; Thu, 28 Apr 2022 07:06:47 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=+HiZWJedwnd+c/Tkmmt4j/ZyKHb1bvbytnlrFNKUIOw=; b=SHWvTsGer/QPJoam2b/0IZ6Dw7m+c/+OIfEjdAnIRd0+W5Z2A+LP0unnNG2HplrpQ/W+ t8fhlq1h0aTLnhgudWkGzFgHrq2/ZsN6sjvmXNm+ouuEeAuWmmy+3TLwESHMsuDV39FC j7ZpQlTQlHsByedwY8I8muu47HdXsFZLgvPmcCgsgq/SzP35d/YhvRRn5SmJ5LH8tt3W Xh5nMyW3mp4GSUkxTuaSRpomvloPf0T1sg9bCOEZkEnh7/bZbN0b8xHreas7FZbGYCWH 7VgL2YNXfJnzoJ22kLT2QZwO7/6dkyzpZHlc7gnI7C6dmUXpa4e+FJdg1xRONbxRpeiJ 9g== Received: from iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta02.appoci.oracle.com [147.154.18.20]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3fmb1mu6m1-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 28 Apr 2022 07:06:46 +0000 Received: from pps.filterd (iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (8.16.1.2/8.16.1.2) with SMTP id 23S70CEI019512; Thu, 28 Apr 2022 07:06:44 GMT Received: from pps.reinject (localhost [127.0.0.1]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com with ESMTP id 3fm7w634wx-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 28 Apr 2022 07:06:44 +0000 Received: from iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com (iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 23S76cAk007862; Thu, 28 Apr 2022 07:06:44 GMT Received: from ca-common-hq.us.oracle.com (ca-common-hq.us.oracle.com [10.211.9.209]) by iadpaimrmta02.imrmtpd1.prodappiadaev1.oraclevcn.com with ESMTP id 3fm7w634qj-6; Thu, 28 Apr 2022 07:06:44 +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 v23 5/7] fs/lock: add 2 callbacks to lock_manager_operations to resolve conflict Date: Thu, 28 Apr 2022 00:06:33 -0700 Message-Id: <1651129595-6904-6-git-send-email-dai.ngo@oracle.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1651129595-6904-1-git-send-email-dai.ngo@oracle.com> References: <1651129595-6904-1-git-send-email-dai.ngo@oracle.com> X-Proofpoint-GUID: XHNz2fPQW_648w9hfyrRot7PL3MMcvbX X-Proofpoint-ORIG-GUID: XHNz2fPQW_648w9hfyrRot7PL3MMcvbX 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 --- Documentation/filesystems/locking.rst | 4 ++++ fs/locks.c | 45 +++++++++++++++++++++++++++++++---- include/linux/fs.h | 3 +++ 3 files changed, 48 insertions(+), 4 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..d48c3f455657 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -896,6 +896,37 @@ static bool flock_locks_conflict(struct file_lock *caller_fl, return locks_conflict(caller_fl, sys_fl); } +static bool +resolve_lock_conflict_locked(struct file_lock_context *ctx, + struct file_lock *cfl, bool rwsem) +{ + void *owner; + bool ret; + void (*func)(void); + + if (cfl->fl_lmops && cfl->fl_lmops->lm_lock_expirable && + cfl->fl_lmops->lm_expire_lock) { + ret = (*cfl->fl_lmops->lm_lock_expirable)(cfl); + if (!ret) + return false; + owner = cfl->fl_lmops->lm_mod_owner; + if (!owner) + return false; + func = cfl->fl_lmops->lm_expire_lock; + __module_get(owner); + if (rwsem) + percpu_up_read(&file_rwsem); + spin_unlock(&ctx->flc_lock); + (*func)(); + module_put(owner); + if (rwsem) + percpu_down_read(&file_rwsem); + spin_lock(&ctx->flc_lock); + return true; + } + return false; +} + void posix_test_lock(struct file *filp, struct file_lock *fl) { @@ -910,11 +941,14 @@ posix_test_lock(struct file *filp, struct file_lock *fl) } spin_lock(&ctx->flc_lock); +retry: 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 (resolve_lock_conflict_locked(ctx, cfl, false)) + goto retry; + locks_copy_conflock(fl, cfl); + goto out; } fl->fl_type = F_UNLCK; out: @@ -1108,6 +1142,7 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, percpu_down_read(&file_rwsem); spin_lock(&ctx->flc_lock); +retry: /* * New lock request. Walk all POSIX locks and look for conflicts. If * there are any, either return error or put the request on the @@ -1117,6 +1152,8 @@ 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 (resolve_lock_conflict_locked(ctx, fl, true)) + goto retry; 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 {