From patchwork Wed Dec 25 06:59:07 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yang Erkun X-Patchwork-Id: 13920638 Received: from dggsgout11.his.huawei.com (dggsgout11.his.huawei.com [45.249.212.51]) (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 3FE2133991; Wed, 25 Dec 2024 07:02:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.51 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735110175; cv=none; b=JD/8UlbpHgt6Y3lnt846Gpoo9mLEocMZsNdf+KE1AKDnx88CwE3tfWlC1khtzVRDTvszs3xo/gBYmpVsL0dxFPJSflLZSCDgAO0yz1dj0Gri86PfIrk2O8MrY/jWbeGRpLu4a3lXPvOgHbkMyKHu3F+nLdSAvERMFK5f9yaSlZM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735110175; c=relaxed/simple; bh=h8FvtbMGFey6DC4Q+xIfqL4HxGkYXSDYxKfTrOdBfcI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r/BdWmuoU6nb9Kk4ZIf1V5IFyUtTOAeGxwg5O6FJPjRA1ALqHIlO9550mVlDqn2HrzOc94ylQjhxUIWUsBu3OAE+JKgLkTeRmkcmezw5kx2HeEuqail7Du6D2PpqJtMV/vm/2uzRy7e5z00k8KnhXiOJtozj+tB29ZyLsJXLEF4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=45.249.212.51 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.19.163.235]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4YJ2ky5cD4z4f3jqs; Wed, 25 Dec 2024 15:02:34 +0800 (CST) Received: from mail02.huawei.com (unknown [10.116.40.128]) by mail.maildlp.com (Postfix) with ESMTP id 679F61A06DA; Wed, 25 Dec 2024 15:02:49 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.112.188]) by APP4 (Coremail) with SMTP id gCh0CgAHL4MRrmtnO8dPFg--.38269S7; Wed, 25 Dec 2024 15:02:49 +0800 (CST) From: Yang Erkun To: chuck.lever@oracle.com, jlayton@kernel.org, neilb@suse.de, okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com, trondmy@kernel.org, anna@kernel.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: linux-nfs@vger.kernel.org, netdev@vger.kernel.org, yangerkun@huawei.com, yangerkun@huaweicloud.com, liumingrui@huawei.com Subject: [PATCH v2 3/4] SUNRPC: no need get cache ref when protected by rcu Date: Wed, 25 Dec 2024 14:59:07 +0800 Message-ID: <20241225065908.1547645-4-yangerkun@huawei.com> X-Mailer: git-send-email 2.46.1 In-Reply-To: <20241225065908.1547645-1-yangerkun@huawei.com> References: <20241225065908.1547645-1-yangerkun@huawei.com> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: gCh0CgAHL4MRrmtnO8dPFg--.38269S7 X-Coremail-Antispam: 1UD129KBjvJXoW7ZryfXFWktF13JFW3Cr1UAwb_yoW8GF4Dpa 9xCrWxtrW0qry7Xr42yr48Zrn5Cr9xta4Iq3ykCw4rAw15Xr13tFyjgFy29F4DZrs7tr4a vF1UtFW5GryDZaDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUH2b4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUWw A2048vs2IY020Ec7CjxVAFwI0_Xr0E3s1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxS w2x7M28EF7xvwVC0I7IYx2IY67AKxVW5JVW7JwA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxV W8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMc Ij6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_ Jr0_Gr1lF7xvr2IYc2Ij64vIr41lF7Iv64x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YV CY1x02628vn2kIc2xKxwCY1x0262kKe7AKxVW8ZVWrXwCF04k20xvY0x0EwIxGrwCF04k2 0xvEw4C26cxK6c8Ij28IcwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r 1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_GFv_WrylIxkGc2Ij 64vIr41lIxAIcVC0I7IYx2IY67AKxVWUJVWUCwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Cr 0_Gr1UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVW8JVWxJwCI 42IY6I8E87Iv6xkF7I0E14v26r4UJVWxJrUvcSsGvfC2KfnxnUUI43ZEXa7IU04v35UUUU U== Sender: yangerkun@huaweicloud.com X-CM-SenderInfo: 51dqwvhunx0q5kxd4v5lfo033gof0z/ rcu_read_lock/rcu_read_unlock has already provide protection for the pointer we will reference when we call c_show. Therefore, there is no need to obtain a cache reference to help protect cache_head. Additionally, the .put such as expkey_put/svc_export_put will invoke dput, which can sleep and break rcu. Stop get cache reference to fix them all. Fixes: ae74136b4bb6 ("SUNRPC: Allow cache lookups to use RCU protection rather than the r/w spinlock") Suggested-by: NeilBrown Signed-off-by: Yang Erkun --- net/sunrpc/cache.c | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-) diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c index 88f42a27c8cc..cb279eb9ac4b 100644 --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -1438,17 +1438,11 @@ static int c_show(struct seq_file *m, void *p) seq_printf(m, "# expiry=%lld refcnt=%d flags=%lx\n", convert_to_wallclock(cp->expiry_time), kref_read(&cp->ref), cp->flags); - if (!cache_get_rcu(cp)) - return 0; - if (cache_check(cd, cp, NULL)) - /* cache_check does a cache_put on failure */ + if (cache_check_rcu(cd, cp, NULL)) + seq_puts(m, "# "); + else if (cache_is_expired(cd, cp)) seq_puts(m, "# "); - else { - if (cache_is_expired(cd, cp)) - seq_puts(m, "# "); - cache_put(cp, cd); - } return cd->cache_show(m, cd, cp); }