From patchwork Thu Aug 26 16:20:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 12460115 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=-16.9 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 C37ABC43214 for ; Thu, 26 Aug 2021 16:20:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D37E61165 for ; Thu, 26 Aug 2021 16:20:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243151AbhHZQVV (ORCPT ); Thu, 26 Aug 2021 12:21:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:44732 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243125AbhHZQVQ (ORCPT ); Thu, 26 Aug 2021 12:21:16 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 0ECA86113A; Thu, 26 Aug 2021 16:20:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1629994828; bh=lVMs581HKynyNG09W2E9A0In+52Er3vjt2kSDd8eGgg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ASmMF5B/nXBJ7lKpIn6SfjDr4ZZhO90yYfYSdHTBygNauhLHotZq4E073kkyiUqJA OzMbfaokCOTlwW7noQU10gJs+GY53Y6vxcQ/mI848MEZbqoDv9iK2it7hqLmfcvCbO 6iz7VhW6YFG2oAQ5sRhnPiTr1R/YjNEEy4vI8UhGgrfk0j1bNCXd3ZTw3Of8FKmVl4 3FnZKvpVv2iOwCAOo7Aj5Ax22ItmfBy5LFdM20A0mBHuiRngczASMTg6rYZOEhW+u0 Lbr8aw9CiTVpwJdgI+s6Zdgr2kfD9CsXOlBP5N1izNfOaRDnMYGHVJ5pXlDZn/lsrm k5X1U6LK6e0oQ== From: Jeff Layton To: ceph-devel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-fscrypt@vger.kernel.org, dhowells@redhat.com, xiubli@redhat.com, lhenriques@suse.de, khiremat@redhat.com, ebiggers@kernel.org Subject: [RFC PATCH v8 13/24] ceph: make ceph_msdc_build_path use ref-walk Date: Thu, 26 Aug 2021 12:20:03 -0400 Message-Id: <20210826162014.73464-14-jlayton@kernel.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210826162014.73464-1-jlayton@kernel.org> References: <20210826162014.73464-1-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 058480708897..518a1aee967c 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -2487,7 +2487,8 @@ 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; @@ -2504,34 +2505,35 @@ 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? */ @@ -2540,8 +2542,9 @@ 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;