From patchwork Fri Sep 4 16:05:32 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeff Layton X-Patchwork-Id: 11758061 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 30DC292C for ; Fri, 4 Sep 2020 16:06:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 178FE20772 for ; Fri, 4 Sep 2020 16:06:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599235619; bh=DFOG7GZ6OylpP0sQqUAusLwuDKNBcXtVUCDGQyCRqbk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=HWqMCQ10cvBaWhv9I9lfVtEHVmxjla0pK9Bywt7G/yaIGh/kI9VqLXMhistsCH7mR zcM5IIT0EAvug1Dpb9E9ygv43nZWFcscgazTcgZh7Zi0J9KxObH+834Vxf1MMBo7eQ 0qGUKTdTYZ/X/bYGGHgrI6W15/7SfRNaKM9qlH1U= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725966AbgIDQG6 (ORCPT ); Fri, 4 Sep 2020 12:06:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:51384 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727937AbgIDQFu (ORCPT ); Fri, 4 Sep 2020 12:05:50 -0400 Received: from tleilax.com (68-20-15-154.lightspeed.rlghnc.sbcglobal.net [68.20.15.154]) (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 93C2120796; Fri, 4 Sep 2020 16:05:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1599235550; bh=DFOG7GZ6OylpP0sQqUAusLwuDKNBcXtVUCDGQyCRqbk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=veB4VermXqsC1eoPTMoZobeYYssvu+MQH3GV9hYpFf3iF1d5kBIrDiS9Y/txZFw/p 9tR/qzce/hsajAx8rm/lpWimtU1VbjSBkLXe3iYcsEHCAnHBzLrPHU3AErIaARBt5h u+AwJBXIcxwu65YBDhhBLhYcGeWoSq8lzi0q9cZ4= From: Jeff Layton To: ceph-devel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-fscrypt@vger.kernel.org, ebiggers@kernel.org Subject: [RFC PATCH v2 13/18] ceph: make ceph_msdc_build_path use ref-walk Date: Fri, 4 Sep 2020 12:05:32 -0400 Message-Id: <20200904160537.76663-14-jlayton@kernel.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200904160537.76663-1-jlayton@kernel.org> References: <20200904160537.76663-1-jlayton@kernel.org> MIME-Version: 1.0 Sender: linux-fscrypt-owner@vger.kernel.org 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 4107dc64cc8c..e3dc061252d4 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -2327,7 +2327,8 @@ 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; @@ -2344,34 +2345,35 @@ 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; + cur = dget(temp->d_parent); spin_unlock(&temp->d_lock); - temp = READ_ONCE(temp->d_parent); + dput(temp); /* Are we at the root? */ - if (IS_ROOT(temp)) + if (IS_ROOT(cur)) break; /* Are we out of buffer? */ @@ -2380,8 +2382,9 @@ 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;