From patchwork Fri Mar 13 23:53:24 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 11438073 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 CFDD414B4 for ; Fri, 13 Mar 2020 23:56:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA02520752 for ; Fri, 13 Mar 2020 23:56:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728225AbgCMX4g (ORCPT ); Fri, 13 Mar 2020 19:56:36 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:50086 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727769AbgCMXyD (ORCPT ); Fri, 13 Mar 2020 19:54:03 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jCu7t-00B6bj-Q6; Fri, 13 Mar 2020 23:54:01 +0000 From: Al Viro To: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Linus Torvalds Subject: [RFC][PATCH v4 36/69] do_last(): don't bother with keeping got_write in FMODE_OPENED case Date: Fri, 13 Mar 2020 23:53:24 +0000 Message-Id: <20200313235357.2646756-36-viro@ZenIV.linux.org.uk> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200313235357.2646756-1-viro@ZenIV.linux.org.uk> References: <20200313235303.GP23230@ZenIV.linux.org.uk> <20200313235357.2646756-1-viro@ZenIV.linux.org.uk> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Al Viro it's easier to drop it right after lookup_open() and regain if needed (i.e. if we will need to truncate). On the non-FMODE_OPENED path we do that anyway. In case of FMODE_CREATED we won't be needing it. And it's easier to prove correctness that way, especially since the initial failure to get write access is not always fatal; proving that we'll never end up truncating in that case is rather convoluted. Signed-off-by: Al Viro --- fs/namei.c | 31 +++++++++++-------------------- 1 file changed, 11 insertions(+), 20 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 2f8a5d3be784..2eef41f505db 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3191,11 +3191,14 @@ static const char *do_last(struct nameidata *nd, else inode_unlock_shared(dir->d_inode); - if (IS_ERR(dentry)) { - error = PTR_ERR(dentry); - goto out; + if (got_write) { + mnt_drop_write(nd->path.mnt); + got_write = false; } + if (IS_ERR(dentry)) + return ERR_CAST(dentry); + if (file->f_mode & FMODE_OPENED) { if (file->f_mode & FMODE_CREATED) { open_flag &= ~O_TRUNC; @@ -3220,16 +3223,6 @@ static const char *do_last(struct nameidata *nd, goto finish_open_created; } - /* - * If atomic_open() acquired write access it is dropped now due to - * possible mount and symlink following (this might be optimized away if - * necessary...) - */ - if (got_write) { - mnt_drop_write(nd->path.mnt); - got_write = false; - } - finish_lookup: if (nd->depth) put_link(nd); @@ -3250,27 +3243,25 @@ static const char *do_last(struct nameidata *nd, return ERR_PTR(error); audit_inode(nd->name, nd->path.dentry, 0); if (open_flag & O_CREAT) { - error = -EISDIR; if (d_is_dir(nd->path.dentry)) - goto out; + return ERR_PTR(-EISDIR); error = may_create_in_sticky(dir_mode, dir_uid, d_backing_inode(nd->path.dentry)); if (unlikely(error)) - goto out; + return ERR_PTR(error); } - error = -ENOTDIR; if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry)) - goto out; + return ERR_PTR(-ENOTDIR); if (!d_is_reg(nd->path.dentry)) will_truncate = false; +finish_open_created: if (will_truncate) { error = mnt_want_write(nd->path.mnt); if (error) - goto out; + return ERR_PTR(error); got_write = true; } -finish_open_created: error = may_open(&nd->path, acc_mode, open_flag); if (error) goto out;