From patchwork Tue Jul 10 14:01:25 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeffrey Layton X-Patchwork-Id: 10517053 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id CC4946032C for ; Tue, 10 Jul 2018 14:02:01 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id BC8522916B for ; Tue, 10 Jul 2018 14:02:01 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B0AB029164; Tue, 10 Jul 2018 14:02:01 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5BCF12915D for ; Tue, 10 Jul 2018 14:02:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933532AbeGJOBe (ORCPT ); Tue, 10 Jul 2018 10:01:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:34096 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933248AbeGJOBc (ORCPT ); Tue, 10 Jul 2018 10:01:32 -0400 Received: from tleilax.poochiereds.net (cpe-71-70-156-158.nc.res.rr.com [71.70.156.158]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6CA8D208E5; Tue, 10 Jul 2018 14:01:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1531231292; bh=rTBPS2lTBV4tvGy1bAXhJwa9kjE2MD8nXDGQjALKBFQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kArPiVeyLFR9Ai1JHx8cjeNeFfo+Lc0B5XJBttsPV2D37k3niaPTFCnz/IRUGouhj OVvKZ3GNwCOL1Y2AchFNMniIk5RGGd/MvpKyTi5F3APjPC672fasneo4dOappGyvg6 ENIhWxZepsNHe33aaqtZHDoAhEEe3ONMpZvcs9FE= From: Jeff Layton To: viro@ZenIV.linux.org.uk, dhowells@redhat.com Cc: willy@infradead.org, andres@anarazel.de, cmaiolino@redhat.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v2 2/4] errseq: add a new errseq_scrape function Date: Tue, 10 Jul 2018 10:01:25 -0400 Message-Id: <20180710140127.20739-3-jlayton@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180710140127.20739-1-jlayton@kernel.org> References: <20180710140127.20739-1-jlayton@kernel.org> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Jeff Layton To grab the current value of an errseq_t, mark it as seen and then return the value with the seen bit masked off. Signed-off-by: Jeff Layton --- include/linux/errseq.h | 1 + lib/errseq.c | 33 +++++++++++++++++++++++++++++++-- 2 files changed, 32 insertions(+), 2 deletions(-) diff --git a/include/linux/errseq.h b/include/linux/errseq.h index fc2777770768..de165623fa86 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_scrape(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 81f9e33aa7e7..8ded0920eed3 100644 --- a/lib/errseq.c +++ b/lib/errseq.c @@ -108,7 +108,7 @@ 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 hasn't been seen) * @eseq: Pointer to errseq_t to be sampled. * * This function allows callers to initialise their errseq_t variable. @@ -117,7 +117,7 @@ EXPORT_SYMBOL(errseq_set); * see it the next time it checks for an error. * * Context: Any context. - * Return: The current errseq value. + * Return: The current errseq value or 0 if it wasn't previously seen */ errseq_t errseq_sample(errseq_t *eseq) { @@ -130,6 +130,35 @@ errseq_t errseq_sample(errseq_t *eseq) } EXPORT_SYMBOL(errseq_sample); +/** + * errseq_scrape() - Grab current errseq_t value + * @eseq: Pointer to errseq_t to be sampled. + * + * This function allows callers to scrape the current value of an errseq_t. + * Unlike errseq_sample, this will always return the current value with + * the SEEN flag unset, even when the value has not yet been seen. + * + * Context: Any context. + * Return: The current errseq value with ERRSEQ_SEEN masked off + */ +errseq_t errseq_scrape(errseq_t *eseq) +{ + errseq_t old = READ_ONCE(*eseq); + + /* + * 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) { + errseq_t new = old | ERRSEQ_SEEN; + if (old != new) + cmpxchg(eseq, old, new); + } + return old & ~ERRSEQ_SEEN; +} +EXPORT_SYMBOL(errseq_scrape); + /** * errseq_check() - Has an error occurred since a particular sample point? * @eseq: Pointer to errseq_t value to be checked.