On Fri, Dec 11, 2015 at 2:07 PM, H. Peter Anvin <h...@zytor.com> wrote: > On 12/11/15 13:48, Andy Lutomirski wrote: >> On Fri, Dec 11, 2015 at 1:11 PM, Eric W. Biederman >> <ebied...@xmission.com> wrote: >>> Al Viro <v...@zeniv.linux.org.uk> writes: >>> >>>> On Fri, Dec 11, 2015 at 01:40:40PM -0600, Eric W. Biederman wrote: >>>> >>>>> + inode = path.dentry->d_inode; >>>>> + filp->f_path = path; >>>>> + filp->f_inode = inode; >>>>> + filp->f_mapping = inode->i_mapping; >>>>> + path_put(&old); >>>> >>>> Don't. You are creating a fairly subtle constraint on what the code in >>>> fs/open.c and fs/namei.c can do, for no good reason. You can bloody >>>> well maintain the information you need without that. >>> >>> There is a good reason. We can not write a race free version of ptsname >>> without it. >> >> As long as this is for new userspace code, would it make sense to just >> add a new ioctl to ask "does this ptmx fd match this /dev/pts fd?" >> > > For the newinstance case st_dev should match between the master and the > slave. Unfortunately this is not the case for a legacy ptmx, as a > stat() on the master descriptor still returns the st_dev, st_rdev, and > st_ino for the ptmx device node.
Sure, but I'm not talking about stat. I'm saying that we could add a new ioctl that works on any ptmx fd (/dev/ptmx or /dev/pts/ptmx) that answers the question "does this ptmx logically belong to the given devpts filesystem". Since it's not stat, we can make it do whatever we want, including following a link to the devpts instance that isn't f_path or f_inode. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
