From patchwork Mon May 18 17:36:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 225620 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CDF8CC433DF for ; Mon, 18 May 2020 18:21:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AEF4920643 for ; Mon, 18 May 2020 18:21:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589826095; bh=SH8FZeK1r0kMgLiWFQS1MyVZECWgi/jMC86bQKXOmz8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Se7PdZYCpJ0UOv/d7/tXEPNDtR4x5xwlD1Z4zYgxmRmYv7WY8ihk9KpvA+q30HrJ1 OdE26EH4/CWQOW2fi0BTyVhE4w2WS2KA2wsIApQZrrxfPBcji9+iTX2/F0/YJy8u4E lfydakfQWgO202XhllbVU26jQp22+y7X8OSKS4Ag= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730327AbgERRvl (ORCPT ); Mon, 18 May 2020 13:51:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:54444 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730330AbgERRvh (ORCPT ); Mon, 18 May 2020 13:51:37 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 DA0FD20829; Mon, 18 May 2020 17:51:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589824297; bh=SH8FZeK1r0kMgLiWFQS1MyVZECWgi/jMC86bQKXOmz8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NRMXiK2yxZvQ5bdkT6uQxFJ2yGe7d7FGSNmqLi1VaVKVJP3xdgG/aCtpnJ7SKgrBX aOh0OBMV/xp8vi5jL1+NkQaqfPV+zzyQpUdUyqkR8O6XAdqfOstP1/faljnuq5YgDN adVEZU69luHUom3GcMSHAaR0uW376Y3RN8nyIwi8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dave Wysochanski , David Howells , Sasha Levin Subject: [PATCH 4.19 36/80] NFS: Fix fscache super_cookie index_key from changing after umount Date: Mon, 18 May 2020 19:36:54 +0200 Message-Id: <20200518173457.689854455@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200518173450.097837707@linuxfoundation.org> References: <20200518173450.097837707@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Dave Wysochanski [ Upstream commit d9bfced1fbcb35b28d8fbed4e785d2807055ed2b ] Commit 402cb8dda949 ("fscache: Attach the index key and aux data to the cookie") added the index_key and index_key_len parameters to fscache_acquire_cookie(), and updated the callers in the NFS client. One of the callers was inside nfs_fscache_get_super_cookie() and was changed to use the full struct nfs_fscache_key as the index_key. However, a couple members of this structure contain pointers and thus will change each time the same NFS share is remounted. Since index_key is used for fscache_cookie->key_hash and this subsequently is used to compare cookies, the effectiveness of fscache with NFS is reduced to the point at which a umount occurs. Any subsequent remount of the same share will cause a unique NFS super_block index_key and key_hash to be generated for the same data, rendering any prior fscache data unable to be found. A simple reproducer demonstrates the problem. 1. Mount share with 'fsc', create a file, drop page cache systemctl start cachefilesd mount -o vers=3,fsc 127.0.0.1:/export /mnt dd if=/dev/zero of=/mnt/file1.bin bs=4096 count=1 echo 3 > /proc/sys/vm/drop_caches 2. Read file into page cache and fscache, then unmount dd if=/mnt/file1.bin of=/dev/null bs=4096 count=1 umount /mnt 3. Remount and re-read which should come from fscache mount -o vers=3,fsc 127.0.0.1:/export /mnt echo 3 > /proc/sys/vm/drop_caches dd if=/mnt/file1.bin of=/dev/null bs=4096 count=1 4. Check for READ ops in mountstats - there should be none grep READ: /proc/self/mountstats Looking at the history and the removed function, nfs_super_get_key(), we should only use nfs_fscache_key.key plus any uniquifier, for the fscache index_key. Fixes: 402cb8dda949 ("fscache: Attach the index key and aux data to the cookie") Signed-off-by: Dave Wysochanski Signed-off-by: David Howells Signed-off-by: Sasha Levin --- fs/nfs/fscache.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c index 6f45b1a957397..b931169c2bb24 100644 --- a/fs/nfs/fscache.c +++ b/fs/nfs/fscache.c @@ -192,7 +192,8 @@ void nfs_fscache_get_super_cookie(struct super_block *sb, const char *uniq, int /* create a cache index for looking up filehandles */ nfss->fscache = fscache_acquire_cookie(nfss->nfs_client->fscache, &nfs_fscache_super_index_def, - key, sizeof(*key) + ulen, + &key->key, + sizeof(key->key) + ulen, NULL, 0, nfss, 0, true); dfprintk(FSCACHE, "NFS: get superblock cookie (0x%p/0x%p)\n",