From patchwork Mon Aug 14 21:11:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Aring X-Patchwork-Id: 13353301 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 820ECDDBD for ; Mon, 14 Aug 2023 21:11:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1692047486; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MTB6n9Lzh+gnb3QJmth1T9LtSZXZSrD2dMC30pyrg2M=; b=PjvgE6Mmhnio0qtIYdfECkX1nTYEI/+Td39a4kQHjPafqMGMJnShYjFvIt7ZL9VHcEopMV lL+CiFipkXcYzYyhQykqcNqldqi7sMQ7HC+N9AOTUYwLyVzsu28HHHJ4SAj5fMYS4LXVQx aLXfXNrhznlz6x3K4RQGWgCm8VAy8xY= Received: from mimecast-mx02.redhat.com (66.187.233.73 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-635-y8MG4fJXP6KTkDjUXyzaRA-1; Mon, 14 Aug 2023 17:11:23 -0400 X-MC-Unique: y8MG4fJXP6KTkDjUXyzaRA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8ED3E3804060; Mon, 14 Aug 2023 21:11:22 +0000 (UTC) Received: from fs-i40c-03.fs.lab.eng.bos.redhat.com (fs-i40c-03.fs.lab.eng.bos.redhat.com [10.16.224.23]) by smtp.corp.redhat.com (Postfix) with ESMTP id 40DE0C15BAD; Mon, 14 Aug 2023 21:11:22 +0000 (UTC) From: Alexander Aring To: linux-nfs@vger.kernel.org Cc: cluster-devel@redhat.com, ocfs2-devel@lists.linux.dev, linux-fsdevel@vger.kernel.org, teigland@redhat.com, rpeterso@redhat.com, agruenba@redhat.com, trond.myklebust@hammerspace.com, anna@kernel.org, chuck.lever@oracle.com, jlayton@kernel.org Subject: [RFCv2 1/7] lockd: fix race in async lock request handling Date: Mon, 14 Aug 2023 17:11:10 -0400 Message-Id: <20230814211116.3224759-2-aahringo@redhat.com> In-Reply-To: <20230814211116.3224759-1-aahringo@redhat.com> References: <20230814211116.3224759-1-aahringo@redhat.com> Precedence: bulk X-Mailing-List: ocfs2-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 This patch fixes a race in async lock request handling between adding the relevant struct nlm_block to nlm_blocked list after the request was sent by vfs_lock_file() and nlmsvc_grant_deferred() does a lookup of the nlm_block in the nlm_blocked list. It could be that the async request is completed before the nlm_block was added to the list. This would end in a -ENOENT and a kernel log message of "lockd: grant for unknown block". To solve this issue we add the nlm_block before the vfs_lock_file() call to be sure it has been added when a possible nlmsvc_grant_deferred() is called. If the vfs_lock_file() results in an case when it wouldn't be added to nlm_blocked list, the nlm_block struct will be removed from this list again. The introducing of the new B_PENDING_CALLBACK nlm_block flag will handle async lock requests on a pending lock requests as a retry on the caller level to hit the -EAGAIN case. Signed-off-by: Alexander Aring Signed-off-by: Jeff Layton --- fs/lockd/svclock.c | 100 ++++++++++++++++++++++++++---------- include/linux/lockd/lockd.h | 2 + 2 files changed, 74 insertions(+), 28 deletions(-) diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c index c43ccdf28ed9..7d63524bdb81 100644 --- a/fs/lockd/svclock.c +++ b/fs/lockd/svclock.c @@ -133,6 +133,7 @@ nlmsvc_remove_block(struct nlm_block *block) { if (!list_empty(&block->b_list)) { spin_lock(&nlm_blocked_lock); + block->b_flags &= ~B_PENDING_CALLBACK; list_del_init(&block->b_list); spin_unlock(&nlm_blocked_lock); nlmsvc_release_block(block); @@ -232,6 +233,7 @@ nlmsvc_create_block(struct svc_rqst *rqstp, struct nlm_host *host, kref_init(&block->b_count); INIT_LIST_HEAD(&block->b_list); INIT_LIST_HEAD(&block->b_flist); + mutex_init(&block->b_cb_mutex); if (!nlmsvc_setgrantargs(call, lock)) goto failed_free; @@ -289,6 +291,8 @@ static void nlmsvc_free_block(struct kref *kref) dprintk("lockd: freeing block %p...\n", block); + WARN_ON_ONCE(block->b_flags & B_PENDING_CALLBACK); + /* Remove block from file's list of blocks */ list_del_init(&block->b_flist); mutex_unlock(&file->f_mutex); @@ -532,6 +536,13 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file, goto out; } + mutex_lock(&block->b_cb_mutex); + if (block->b_flags & B_PENDING_CALLBACK) + goto pending_request; + + /* Append to list of blocked */ + nlmsvc_insert_block(block, NLM_NEVER); + if (!wait) lock->fl.fl_flags &= ~FL_SLEEP; mode = lock_to_openmode(&lock->fl); @@ -541,9 +552,13 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file, dprintk("lockd: vfs_lock_file returned %d\n", error); switch (error) { case 0: + nlmsvc_remove_block(block); ret = nlm_granted; - goto out; + goto out_cb_mutex; case -EAGAIN: + if (!wait) + nlmsvc_remove_block(block); +pending_request: /* * If this is a blocking request for an * already pending lock request then we need @@ -552,26 +567,29 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file, if (wait) break; ret = async_block ? nlm_lck_blocked : nlm_lck_denied; - goto out; + goto out_cb_mutex; case FILE_LOCK_DEFERRED: + block->b_flags |= B_PENDING_CALLBACK; + if (wait) break; /* Filesystem lock operation is in progress Add it to the queue waiting for callback */ ret = nlmsvc_defer_lock_rqst(rqstp, block); - goto out; + goto out_cb_mutex; case -EDEADLK: + nlmsvc_remove_block(block); ret = nlm_deadlock; - goto out; + goto out_cb_mutex; default: /* includes ENOLCK */ + nlmsvc_remove_block(block); ret = nlm_lck_denied_nolocks; - goto out; + goto out_cb_mutex; } ret = nlm_lck_blocked; - - /* Append to list of blocked */ - nlmsvc_insert_block(block, NLM_NEVER); +out_cb_mutex: + mutex_unlock(&block->b_cb_mutex); out: mutex_unlock(&file->f_mutex); nlmsvc_release_block(block); @@ -728,34 +746,60 @@ nlmsvc_update_deferred_block(struct nlm_block *block, int result) block->b_flags |= B_TIMED_OUT; } +static int __nlmsvc_grant_deferred(struct nlm_block *block, + struct file_lock *fl, + int result) +{ + int rc = 0; + + dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n", + block, block->b_flags); + if (block->b_flags & B_QUEUED) { + if (block->b_flags & B_TIMED_OUT) { + rc = -ENOLCK; + goto out; + } + nlmsvc_update_deferred_block(block, result); + } else if (result == 0) + block->b_granted = 1; + + nlmsvc_insert_block_locked(block, 0); + svc_wake_up(block->b_daemon); +out: + return rc; +} + static int nlmsvc_grant_deferred(struct file_lock *fl, int result) { - struct nlm_block *block; - int rc = -ENOENT; + struct nlm_block *iter, *block = NULL; + int rc; spin_lock(&nlm_blocked_lock); - list_for_each_entry(block, &nlm_blocked, b_list) { - if (nlm_compare_locks(&block->b_call->a_args.lock.fl, fl)) { - dprintk("lockd: nlmsvc_notify_blocked block %p flags %d\n", - block, block->b_flags); - if (block->b_flags & B_QUEUED) { - if (block->b_flags & B_TIMED_OUT) { - rc = -ENOLCK; - break; - } - nlmsvc_update_deferred_block(block, result); - } else if (result == 0) - block->b_granted = 1; - - nlmsvc_insert_block_locked(block, 0); - svc_wake_up(block->b_daemon); - rc = 0; + list_for_each_entry(iter, &nlm_blocked, b_list) { + if (nlm_compare_locks(&iter->b_call->a_args.lock.fl, fl)) { + kref_get(&iter->b_count); + block = iter; break; } } spin_unlock(&nlm_blocked_lock); - if (rc == -ENOENT) - printk(KERN_WARNING "lockd: grant for unknown block\n"); + + if (!block) { + pr_warn("lockd: grant for unknown pending block\n"); + return -ENOENT; + } + + /* don't interfere with nlmsvc_lock() */ + mutex_lock(&block->b_cb_mutex); + block->b_flags &= ~B_PENDING_CALLBACK; + + spin_lock(&nlm_blocked_lock); + WARN_ON_ONCE(list_empty(&block->b_list)); + rc = __nlmsvc_grant_deferred(block, fl, result); + spin_unlock(&nlm_blocked_lock); + mutex_unlock(&block->b_cb_mutex); + + nlmsvc_release_block(block); return rc; } diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h index f42594a9efe0..91f55458f5fc 100644 --- a/include/linux/lockd/lockd.h +++ b/include/linux/lockd/lockd.h @@ -185,10 +185,12 @@ struct nlm_block { struct nlm_file * b_file; /* file in question */ struct cache_req * b_cache_req; /* deferred request handling */ struct cache_deferred_req * b_deferred_req; + struct mutex b_cb_mutex; /* callback mutex */ unsigned int b_flags; /* block flags */ #define B_QUEUED 1 /* lock queued */ #define B_GOT_CALLBACK 2 /* got lock or conflicting lock */ #define B_TIMED_OUT 4 /* filesystem too slow to respond */ +#define B_PENDING_CALLBACK 8 /* pending callback for lock request */ }; /*