From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: [PATCH 08/13] VFS/namei: enhance follow_link to support RCU-walk. Date: Mon, 16 Mar 2015 15:43:20 +1100 Message-ID: <20150316044320.23648.68027.stgit@notabene.brown> References: <20150316043602.23648.52734.stgit@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Al Viro Return-path: In-Reply-To: <20150316043602.23648.52734.stgit@notabene.brown> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org If LOOKUP_RCU is set, follow_link will not take/drop reference counts. Replace cond_resched() with _cond_resched() as the latter is a no-op if rcu_read_lock() is held while the former will give a warning in that case. Signed-off-by: NeilBrown --- fs/namei.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 1663d21a3eb4..536e0254f5f1 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -906,7 +906,8 @@ follow_link(struct path *link, struct nameidata *nd, void **p) if (unlikely(current->nameidata->total_link_count >= 40)) goto out_put_nd_path; - cond_resched(); + /* If rcu_read_locked(), this will not resched, and will not warn */ + _cond_resched(); current->nameidata->total_link_count++; if (nd->flags & LOOKUP_RCU) { @@ -936,11 +937,17 @@ follow_link(struct path *link, struct nameidata *nd, void **p) return PTR_ERR(s); } if (*s == '/') { - if (!nd->root.mnt) - set_root(nd); - path_put(&nd->path); - nd->path = nd->root; - path_get(&nd->root); + if (nd->flags & LOOKUP_RCU) { + if (!nd->root.mnt) + set_root_rcu(nd); + nd->path = nd->root; + } else { + if (!nd->root.mnt) + set_root(nd); + path_put(&nd->path); + nd->path = nd->root; + path_get(&nd->root); + } nd->flags |= LOOKUP_JUMPED; } nd->inode = nd->path.dentry->d_inode;