From patchwork Fri Mar 26 17:32:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 12167131 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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNWANTED_LANGUAGE_BODY, USER_AGENT_GIT autolearn=ham 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 3949EC433F8 for ; Fri, 26 Mar 2021 17:33:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08A0561A28 for ; Fri, 26 Mar 2021 17:33:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230287AbhCZRcq (ORCPT ); Fri, 26 Mar 2021 13:32:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:48320 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230226AbhCZRcg (ORCPT ); Fri, 26 Mar 2021 13:32:36 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 112F461A38; Fri, 26 Mar 2021 17:32:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616779955; bh=4XcyS5QRnxzJ2QPNa/OB7VEWhXxN/pU4y8nOh/FIOKs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=G9nuGxsFK1o4ixOTM14G1vDK6nOFJ9MIwGnyMGSmTOA25RasP3dQN9XZ2hdCIcL4i bd69+wvrMdU+L3E85tLKDNGCJXko80BMJFtSw7eENXGHvN8YuqtDHM/CBfjdEvnRAu 5A70jMsn4F5e2udIsN5W3xRgT9wW4wog+ZCjjVbFT08pX6rHf/rXxd2QerFnl+Ox6A ML7CyrizroIm2FtNkLQ+rTC20RspiPoKy9IpwBNgxNnIuM9Z2iVr705vMhq6TlmSfy vFTq/c0yY9fjJx64G3qUCF6knCtCG6U7fYR3rA4wxGrv5Pj1ImfF4o2vFor8w9w8SU uqWKwn9EiY+wA== From: Jeff Layton To: ceph-devel@vger.kernel.org Cc: linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [RFC PATCH v5 09/19] ceph: make ceph_msdc_build_path use ref-walk Date: Fri, 26 Mar 2021 13:32:17 -0400 Message-Id: <20210326173227.96363-10-jlayton@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210326173227.96363-1-jlayton@kernel.org> References: <20210326173227.96363-1-jlayton@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org Encryption potentially requires allocation, at which point we'll need to be in a non-atomic context. Convert ceph_msdc_build_path to take dentry spinlocks and references instead of using rcu_read_lock to walk the path. This is slightly less efficient, and we may want to eventually allow using RCU when the leaf dentry isn't encrypted. Signed-off-by: Jeff Layton --- fs/ceph/mds_client.c | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index e3284de74ca4..d7a40e83f12f 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -2323,7 +2323,8 @@ static inline u64 __get_oldest_tid(struct ceph_mds_client *mdsc) char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase, int stop_on_nosnap) { - struct dentry *temp; + struct dentry *cur; + struct inode *inode; char *path; int pos; unsigned seq; @@ -2340,34 +2341,35 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase, path[pos] = '\0'; seq = read_seqbegin(&rename_lock); - rcu_read_lock(); - temp = dentry; + cur = dget(dentry); for (;;) { - struct inode *inode; + struct dentry *temp; - spin_lock(&temp->d_lock); - inode = d_inode(temp); + spin_lock(&cur->d_lock); + inode = d_inode(cur); if (inode && ceph_snap(inode) == CEPH_SNAPDIR) { dout("build_path path+%d: %p SNAPDIR\n", - pos, temp); - } else if (stop_on_nosnap && inode && dentry != temp && + pos, cur); + } else if (stop_on_nosnap && inode && dentry != cur && ceph_snap(inode) == CEPH_NOSNAP) { - spin_unlock(&temp->d_lock); + spin_unlock(&cur->d_lock); pos++; /* get rid of any prepended '/' */ break; } else { - pos -= temp->d_name.len; + pos -= cur->d_name.len; if (pos < 0) { - spin_unlock(&temp->d_lock); + spin_unlock(&cur->d_lock); break; } - memcpy(path + pos, temp->d_name.name, temp->d_name.len); + memcpy(path + pos, cur->d_name.name, cur->d_name.len); } + temp = cur; spin_unlock(&temp->d_lock); - temp = READ_ONCE(temp->d_parent); + cur = dget_parent(temp); + dput(temp); /* Are we at the root? */ - if (IS_ROOT(temp)) + if (IS_ROOT(cur)) break; /* Are we out of buffer? */ @@ -2376,8 +2378,9 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase, path[pos] = '/'; } - base = ceph_ino(d_inode(temp)); - rcu_read_unlock(); + inode = d_inode(cur); + base = inode ? ceph_ino(inode) : 0; + dput(cur); if (read_seqretry(&rename_lock, seq)) goto retry;