From patchwork Tue Feb 7 17:41:46 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 13131953 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 9293FC636D3 for ; Tue, 7 Feb 2023 17:41:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231982AbjBGRl5 (ORCPT ); Tue, 7 Feb 2023 12:41:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45582 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231994AbjBGRly (ORCPT ); Tue, 7 Feb 2023 12:41:54 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E70D2C145 for ; Tue, 7 Feb 2023 09:41:52 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 910B6B81A63 for ; Tue, 7 Feb 2023 17:41:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D9805C433EF; Tue, 7 Feb 2023 17:41:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1675791710; bh=NLlOzjvYsav0jnhRBiJKu+LtURlnW7UQe3kR8LUFaMA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=thDdyXFhL/e3j/WV9x19elWNogSXLLlRRjnDymW1I1DDruzUes+gB+klDmiYS0OsC GwL9SUfINb+pZmUF4W7zUMdH1G5OVG8YxaEXAclas6Lp4qzRMD2Y3UkyQ8gg+Vszdy GVzppgCpvRZOMZTNaFnmZsMCARgq37qyYXo30JCDOq8b58f793KU9MPa6o8xP1Dh9O Z3HRYZm4rQCZm/Wje9n3WDoCsBobiTVQDeEW+6JyfoXLHza8kfA0EEOUxcYXYCwVqq V7YlsirsdfLPbEKwjRPH4t36dMrmqfZhrltMt01TBUzVRsxKHEbrt34c5E1RrXtrzk idBFRz3u8Wf/Q== From: Jeff Layton To: chuck.lever@oracle.com, trond.myklebust@hammerspace.com Cc: linux-nfs@vger.kernel.org Subject: [RFC PATCH 1/2] errseq: add a new errseq_fetch helper Date: Tue, 7 Feb 2023 12:41:46 -0500 Message-Id: <20230207174147.205482-2-jlayton@kernel.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230207174147.205482-1-jlayton@kernel.org> References: <20230207174147.205482-1-jlayton@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org We need to be able to fetch the current value for nfsd's write verifiers, but in the event that the value hasn't been SEEN, we don't want to return a 0. Resurrect the old errseq_sample routine (before Willy fixed it) and rechristen it as errseq_fetch. Signed-off-by: Jeff Layton --- include/linux/errseq.h | 1 + lib/errseq.c | 33 ++++++++++++++++++++++++++++++++- 2 files changed, 33 insertions(+), 1 deletion(-) diff --git a/include/linux/errseq.h b/include/linux/errseq.h index fc2777770768..13a731236c9b 100644 --- a/include/linux/errseq.h +++ b/include/linux/errseq.h @@ -9,6 +9,7 @@ typedef u32 errseq_t; errseq_t errseq_set(errseq_t *eseq, int err); errseq_t errseq_sample(errseq_t *eseq); +errseq_t errseq_fetch(errseq_t *eseq); int errseq_check(errseq_t *eseq, errseq_t since); int errseq_check_and_advance(errseq_t *eseq, errseq_t *since); #endif diff --git a/lib/errseq.c b/lib/errseq.c index 93e9b94358dc..f243b7dc36f5 100644 --- a/lib/errseq.c +++ b/lib/errseq.c @@ -109,7 +109,7 @@ errseq_t errseq_set(errseq_t *eseq, int err) EXPORT_SYMBOL(errseq_set); /** - * errseq_sample() - Grab current errseq_t value. + * errseq_sample() - Grab current errseq_t value (or 0 if it's unseen) * @eseq: Pointer to errseq_t to be sampled. * * This function allows callers to initialise their errseq_t variable. @@ -131,6 +131,37 @@ errseq_t errseq_sample(errseq_t *eseq) } EXPORT_SYMBOL(errseq_sample); +/** + * errseq_fetch() - Grab current errseq_t value + * @eseq: Pointer to errseq_t to be sampled. + * + * This function grabs the current errseq_t value, and returns it, + * and marks the value as SEEN. This differs from a "sample" in that we + * grab the actual value even if it has not been seen before (instead of + * returning 0 in that case). + * + * Context: Any context. + * Return: The current errseq value. + */ +errseq_t errseq_fetch(errseq_t *eseq) +{ + errseq_t old = READ_ONCE(*eseq); + errseq_t new = old; + + /* + * For the common case of no errors ever having been set, we can skip + * marking the SEEN bit. Once an error has been set, the value will + * never go back to zero. + */ + if (old != 0) { + new |= ERRSEQ_SEEN; + if (old != new) + cmpxchg(eseq, old, new); + } + return new; +} +EXPORT_SYMBOL(errseq_fetch); + /** * errseq_check() - Has an error occurred since a particular sample point? * @eseq: Pointer to errseq_t value to be checked.