From mboxrd@z Thu Jan 1 00:00:00 1970 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 45EE185947 for ; Mon, 29 Jul 2024 19:36:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722281820; cv=none; b=K216HT5UeBCe/hNCk7NLyRj4IfYASxV5my7Pq6rTIDLgGVl0zUOeohzNxlXmNDuio4SWivnh1o8khhFOe9n4JQ+Y3aQMp0cMk7jXOkuBbfVQhALeE4u/hW1XJp28syN4uEvuVkt7J20crgbzToy5B04AngOD0UhKsTQwLZSHa6E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722281820; c=relaxed/simple; bh=8Hoo1DrLpdD/YIF5wSHnDMauZj+lwETZmL77fJs+S3Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=qsndIzcU6qtBCLEV88OnIyAgKnluf4K/LTQAfs6EwNWnOvvbxzhm35GjhDDEfhNdwW00y93lUDr8aDoxLdw2XQLaxYAc/eVy/2A5ZDDWTzuwivSe8l+Vuk3wOtolfTvZo64po5ht9nVpF6qpnkN410iRT/o/MYcXRswKehYJFoE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=JJfbmSxq; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="JJfbmSxq" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1722281818; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=R/nREdBAI5U3tXdONd+0dX1YEdm6KfkO93wt/SjZ7rk=; b=JJfbmSxqbJJ/SdfpKNeHU6NYhiv3f3hCJsIAGyetGdX3Op6e/7X7SJjlZ2W4hqZNy1J7jE mFR+HWeVjP38GHzqqbtFElO2ixLXLY9iLZRX/ei0av5wvcaOHGcPuG3n8KKvHCTILydDUN 02K8Vei2PdMfLQC7yAfX3PDhioKoUu0= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-339-CgVQYv-eMYOe3ktfDyHSeA-1; Mon, 29 Jul 2024 15:36:44 -0400 X-MC-Unique: CgVQYv-eMYOe3ktfDyHSeA-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B42C61955D4B for ; Mon, 29 Jul 2024 19:36:43 +0000 (UTC) Received: from fs-i40c-03.mgmt.fast.eng.rdu2.dc.redhat.com (fs-i40c-03.mgmt.fast.eng.rdu2.dc.redhat.com [10.6.24.150]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 14B321955D42; Mon, 29 Jul 2024 19:36:42 +0000 (UTC) From: Alexander Aring To: teigland@redhat.com Cc: gfs2@lists.linux.dev, aahringo@redhat.com Subject: [PATCH v6.11-rc1 08/10] dlm: move dlm_search_rsb_tree() out of lock Date: Mon, 29 Jul 2024 15:36:28 -0400 Message-ID: <20240729193630.3344082-8-aahringo@redhat.com> In-Reply-To: <20240729193630.3344082-1-aahringo@redhat.com> References: <20240729193630.3344082-1-aahringo@redhat.com> Precedence: bulk X-Mailing-List: gfs2@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII"; x-default=true The rhashtable structure is lockless for readers such as rhashtable_lookup_fast(). It should be save to call this lookup functionality out of holding ls_rsbtbl_lock to get the rsb pointer out of the hash. This reduce the contention time of ls_rsbtbl_lock in some cases. We still need to check if the rsb is part of the check as this state can be changed while ls_rsbtbl_lock is not held. If its part of the rhashtable data structure we take a reference to be sure it will not be freed after we drop the ls_rsbtbl_lock read lock. Signed-off-by: Alexander Aring --- fs/dlm/lock.c | 77 +++++++++++++++++++++++++++++++-------------------- 1 file changed, 47 insertions(+), 30 deletions(-) diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c index 8bf3654f4827..9d3ec359d5e3 100644 --- a/fs/dlm/lock.c +++ b/fs/dlm/lock.c @@ -733,11 +733,13 @@ static int find_rsb_dir(struct dlm_ls *ls, const void *name, int len, } retry: + error = dlm_search_rsb_tree(&ls->ls_rsbtbl, name, len, &r); + if (error) + goto do_new; /* check if the rsb is active under read lock - likely path */ read_lock_bh(&ls->ls_rsbtbl_lock); - error = dlm_search_rsb_tree(&ls->ls_rsbtbl, name, len, &r); - if (error) { + if (!rsb_flag(r, RSB_HASHED)) { read_unlock_bh(&ls->ls_rsbtbl_lock); goto do_new; } @@ -918,11 +920,13 @@ static int find_rsb_nodir(struct dlm_ls *ls, const void *name, int len, int error; retry: + error = dlm_search_rsb_tree(&ls->ls_rsbtbl, name, len, &r); + if (error) + goto do_new; /* check if the rsb is in active state under read lock - likely path */ read_lock_bh(&ls->ls_rsbtbl_lock); - error = dlm_search_rsb_tree(&ls->ls_rsbtbl, name, len, &r); - if (error) { + if (!rsb_flag(r, RSB_HASHED)) { read_unlock_bh(&ls->ls_rsbtbl_lock); goto do_new; } @@ -1276,36 +1280,38 @@ static int _dlm_master_lookup(struct dlm_ls *ls, int from_nodeid, const char *na } retry: + error = dlm_search_rsb_tree(&ls->ls_rsbtbl, name, len, &r); + if (error) + goto not_found; /* check if the rsb is active under read lock - likely path */ read_lock_bh(&ls->ls_rsbtbl_lock); - error = dlm_search_rsb_tree(&ls->ls_rsbtbl, name, len, &r); - if (!error) { - if (rsb_flag(r, RSB_INACTIVE)) { - read_unlock_bh(&ls->ls_rsbtbl_lock); - goto do_inactive; - } - - /* because the rsb is active, we need to lock_rsb before - * checking/changing re_master_nodeid - */ + if (!rsb_flag(r, RSB_HASHED)) { + read_unlock_bh(&ls->ls_rsbtbl_lock); + goto not_found; + } - hold_rsb(r); + if (rsb_flag(r, RSB_INACTIVE)) { read_unlock_bh(&ls->ls_rsbtbl_lock); - lock_rsb(r); + goto do_inactive; + } - __dlm_master_lookup(ls, r, our_nodeid, from_nodeid, false, - flags, r_nodeid, result); + /* because the rsb is active, we need to lock_rsb before + * checking/changing re_master_nodeid + */ - /* the rsb was active */ - unlock_rsb(r); - put_rsb(r); + hold_rsb(r); + read_unlock_bh(&ls->ls_rsbtbl_lock); + lock_rsb(r); - return 0; - } else { - read_unlock_bh(&ls->ls_rsbtbl_lock); - goto not_found; - } + __dlm_master_lookup(ls, r, our_nodeid, from_nodeid, false, + flags, r_nodeid, result); + + /* the rsb was active */ + unlock_rsb(r); + put_rsb(r); + + return 0; do_inactive: /* unlikely path - check if still part of ls_rsbtbl */ @@ -1403,14 +1409,14 @@ void dlm_dump_rsb_name(struct dlm_ls *ls, const char *name, int len) struct dlm_rsb *r = NULL; int error; - read_lock_bh(&ls->ls_rsbtbl_lock); + rcu_read_lock(); error = dlm_search_rsb_tree(&ls->ls_rsbtbl, name, len, &r); if (!error) goto out; dlm_dump_rsb(r); out: - read_unlock_bh(&ls->ls_rsbtbl_lock); + rcu_read_unlock(); } static void deactivate_rsb(struct kref *kref) @@ -4309,16 +4315,27 @@ static void receive_remove(struct dlm_ls *ls, const struct dlm_message *ms) memset(name, 0, sizeof(name)); memcpy(name, ms->m_extra, len); - write_lock_bh(&ls->ls_rsbtbl_lock); - + rcu_read_lock(); rv = dlm_search_rsb_tree(&ls->ls_rsbtbl, name, len, &r); if (rv) { + rcu_read_unlock(); /* should not happen */ log_error(ls, "%s from %d not found %s", __func__, from_nodeid, name); + return; + } + + write_lock_bh(&ls->ls_rsbtbl_lock); + if (!rsb_flag(r, RSB_HASHED)) { + rcu_read_unlock(); write_unlock_bh(&ls->ls_rsbtbl_lock); + /* should not happen */ + log_error(ls, "%s from %d got removed during removal %s", + __func__, from_nodeid, name); return; } + /* at this stage the rsb can only being freed here */ + rcu_read_unlock(); if (!rsb_flag(r, RSB_INACTIVE)) { if (r->res_master_nodeid != from_nodeid) { -- 2.43.0