Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753970Ab0GLID3 (ORCPT ); Mon, 12 Jul 2010 04:03:29 -0400 Received: from fxip-0047f.externet.hu ([88.209.222.127]:49125 "EHLO pomaz-ex.szeredi.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751018Ab0GLID1 (ORCPT ); Mon, 12 Jul 2010 04:03:27 -0400 To: "Aneesh Kumar K.V" CC: hch@infradead.org, viro@zeniv.linux.org.uk, adilger@sun.com, corbet@lwn.net, neilb@suse.de, npiggin@suse.de, hooanon05@yahoo.co.jp, bfields@fieldses.org, linux-fsdevel@vger.kernel.org, sfrench@us.ibm.com, philippe.deniel@CEA.FR, linux-kernel@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com In-reply-to: <1278916545-19751-6-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Subject: Re: [PATCH -V16 05/12] vfs: Support null pathname in readlink References: <1278916545-19751-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1278916545-19751-6-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Message-Id: From: Miklos Szeredi Date: Mon, 12 Jul 2010 10:02:55 +0200 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2788 Lines: 92 On Mon, 12 Jul 2010, Aneesh Kumar K.V wrote: > From: NeilBrown > > This enables to use readlink to get the link target name > from a file descriptor point to the link. This can be used > with open_by_handle syscall that returns a file descriptor for a link. > We can then use this file descriptor to get the target name. > > This is similar to utimensat(2) interface We could introduce pair of new helper functions to extract the common code from do_utimes() and this: err = lookup_path_at(dfd, filename, atflags, &path, &file); /* do something with path */ put_path_at(&path, file); Thanks, Miklos > Signed-off-by: NeilBrown > Signed-off-by: Aneesh Kumar K.V > --- > fs/stat.c | 30 ++++++++++++++++++++++-------- > 1 files changed, 22 insertions(+), 8 deletions(-) > > diff --git a/fs/stat.c b/fs/stat.c > index c4ecd52..a66a0ef 100644 > --- a/fs/stat.c > +++ b/fs/stat.c > @@ -284,26 +284,40 @@ SYSCALL_DEFINE2(newfstat, unsigned int, fd, struct stat __user *, statbuf) > SYSCALL_DEFINE4(readlinkat, int, dfd, const char __user *, pathname, > char __user *, buf, int, bufsiz) > { > - struct path path; > - int error; > + int error = 0, fput_needed; > + struct path path, *pp; > + struct file *file = NULL; > > if (bufsiz <= 0) > return -EINVAL; > > - error = user_path_at(dfd, pathname, 0, &path); > + if (pathname == NULL && dfd != AT_FDCWD) { > + file = fget_light(dfd, &fput_needed); > + > + if (file) > + pp = &file->f_path; > + else > + error = -EBADF; > + } else { > + error = user_path_at(dfd, pathname, 0, &path); > + pp = &path; > + } > if (!error) { > - struct inode *inode = path.dentry->d_inode; > + struct inode *inode = pp->dentry->d_inode; > > error = -EINVAL; > if (inode->i_op->readlink) { > - error = security_inode_readlink(path.dentry); > + error = security_inode_readlink(pp->dentry); > if (!error) { > - touch_atime(path.mnt, path.dentry); > - error = inode->i_op->readlink(path.dentry, > + touch_atime(pp->mnt, pp->dentry); > + error = inode->i_op->readlink(pp->dentry, > buf, bufsiz); > } > } > - path_put(&path); > + if (file) > + fput_light(file, fput_needed); > + else > + path_put(&path); > } > return error; > } > -- > 1.7.2.rc1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/