From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?windows-1252?Q?Micka=EBl_Sala=FCn?= Subject: Re: procfs/d_invalidate break userland Date: Thu, 23 Apr 2015 09:00:15 +0200 Message-ID: <5538987F.5090402@digikod.net> References: <5538318E.6000405@digikod.net> <20150422235135.GY889@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="6p0JHrMr31vAdfS3fsu4amntjqfmPj62G" Cc: Linux-Fsdevel , "Eric W. Biederman" , Miklos Szeredi , Greg Kroah-Hartman To: Al Viro Return-path: Received: from 19.mo1.mail-out.ovh.net ([178.32.97.206]:36794 "EHLO 19.mo1.mail-out.ovh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755373AbbDWISO (ORCPT ); Thu, 23 Apr 2015 04:18:14 -0400 Received: from mail191.ha.ovh.net (gw6.ovh.net [213.251.189.206]) by mo1.mail-out.ovh.net (Postfix) with SMTP id AF702101C260 for ; Thu, 23 Apr 2015 09:01:16 +0200 (CEST) In-Reply-To: <20150422235135.GY889@ZenIV.linux.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --6p0JHrMr31vAdfS3fsu4amntjqfmPj62G Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 04/23/2015 01:51 AM, Al Viro wrote: > On Thu, Apr 23, 2015 at 01:41:02AM +0200, Micka=EBl Sala=FCn wrote: >> Hi, >> >> For your information, the commit bbd5192412fdedbae00888316bfe350bf89d0= 458 (proc: Update proc_flush_task_mnt to use d_invalidate), in the v3.17,= break some userland use of procfs. >> >> In a user namespace, I'm using /proc//task//fdinfo to mount = a tmpfs, chdir into it, terminate the thread, and use the tmpfs as = a private working directory for PID 1. This trick is useful to disconnect= /d_drop a directory from the current file system and make it inaccessible= to the other processes (kind of an O_TMPFILE for directory). >> >> With the v3.17 this is no more possible because it's no more possible = to mount anything in this tmpfs nor use the previously mounted file syste= ms in this tmpfs. >> >> The new d_invalidate is really good to lazily invalidate/umount an ent= ire hierarchy but I'm not sure the intention was to remove this useful "f= eature" ;) >=20 > And what will happen if you mount stuff there and exit? Dirty filesyst= em > after reboot? >=20 I didn't notice any but only do tmpfs or bind mounts because of user name= space anyway. --6p0JHrMr31vAdfS3fsu4amntjqfmPj62G Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEcBAEBCgAGBQJVOJh/AAoJECLe/t9zvWqVG2UH/iK4D7reVGcweoOFU3uGlfMH dhCkmUQDGjJKyqRLL4CD1mjGkWNGhJ6wLdZt0HTZkqJMKAqcaIBUi2/TNjxm6MoQ Zyh3Q+hIw6/HYWNAqRBVyZiNlLpl2ra0GKZ0af5nEcDHcdRuYUAum7hphrEIImGz miJ2QimekELGUydV7D6xSmOyL+2UzHCIbf8SoJFksuTGk451CnTiPlP9aLUtgHTS 5BIm2KxrlmSQFREKdrndEXOKGhKAfKtqHo6rPDxv260Z/P0sKygROqgZG0KDCTKU 0PGDzcwHeuGUw/wMf/Z9e2M8k0U3nqIBNy+ShEOUMlRQGmcwe71YmPQvzAKWOHs= =rxof -----END PGP SIGNATURE----- --6p0JHrMr31vAdfS3fsu4amntjqfmPj62G--