From owner-freebsd-arch@FreeBSD.ORG Wed May 14 09:32:56 2008 Return-Path: Delivered-To: arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id DEBD1106566B for ; Wed, 14 May 2008 09:32:56 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from anti-4.kiev.sovam.com (anti-4.kiev.sovam.com [62.64.120.202]) by mx1.freebsd.org (Postfix) with ESMTP id 7432A8FC19 for ; Wed, 14 May 2008 09:32:56 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from [212.82.216.226] (helo=skuns.kiev.zoral.com.ua) by anti-4.kiev.sovam.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.67) (envelope-from ) id 1JwDLY-000DAK-Vc for arch@freebsd.org; Wed, 14 May 2008 12:32:54 +0300 Received: from deviant.kiev.zoral.com.ua (root@deviant.kiev.zoral.com.ua [10.1.1.148]) by skuns.kiev.zoral.com.ua (8.14.2/8.14.2) with ESMTP id m4E9WQ9P017779 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 14 May 2008 12:32:26 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.14.2/8.14.2) with ESMTP id m4E9WNCC043603; Wed, 14 May 2008 12:32:23 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.2/8.14.2/Submit) id m4E9WNW0043602; Wed, 14 May 2008 12:32:23 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Wed, 14 May 2008 12:32:23 +0300 From: Kostik Belousov To: Jeff Roberson Message-ID: <20080514093223.GN18958@deviant.kiev.zoral.com.ua> References: <20080504171002.GN18958@deviant.kiev.zoral.com.ua> <20080510214812.Y954@desktop> <20080511115030.GV18958@deviant.kiev.zoral.com.ua> <20080511115815.GW18958@deviant.kiev.zoral.com.ua> <20080511153926.T954@desktop> <20080512101607.GC18958@deviant.kiev.zoral.com.ua> <20080512100202.W954@desktop> <20080513093734.GF18958@deviant.kiev.zoral.com.ua> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="5glgGqCv79Y86mRH" Content-Disposition: inline In-Reply-To: <20080513093734.GF18958@deviant.kiev.zoral.com.ua> User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: ClamAV version 0.91.2, clamav-milter version 0.91.2 on skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.2.4 X-Spam-Checker-Version: SpamAssassin 3.2.4 (2008-01-01) on skuns.kiev.zoral.com.ua X-Scanner-Signature: e3b942a55251a77f49093e43cd2f7d51 X-DrWeb-checked: yes X-SpamTest-Envelope-From: kostikbel@gmail.com X-SpamTest-Group-ID: 00000000 X-SpamTest-Header: Not Detected X-SpamTest-Info: Profiles 2811 [May 13 2008] X-SpamTest-Info: helo_type=3 X-SpamTest-Method: none X-SpamTest-Rate: 0 X-SpamTest-Status: Not detected X-SpamTest-Status-Extended: not_detected X-SpamTest-Version: SMTP-Filter Version 3.0.0 [0278], KAS30/Release Cc: arch@freebsd.org Subject: Re: Per-open file private data for the cdevs X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 14 May 2008 09:32:56 -0000 --5glgGqCv79Y86mRH Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, May 13, 2008 at 12:37:34PM +0300, Kostik Belousov wrote: > On Mon, May 12, 2008 at 10:03:14AM -1000, Jeff Roberson wrote: > >=20 > > On Mon, 12 May 2008, Kostik Belousov wrote: > >=20 > > >On Sun, May 11, 2008 at 03:40:14PM -1000, Jeff Roberson wrote: > > >> > > >>On Sun, 11 May 2008, Kostik Belousov wrote: > > >> > > >>>On Sun, May 11, 2008 at 02:50:30PM +0300, Kostik Belousov wrote: > > >>>>On Sat, May 10, 2008 at 09:53:12PM -1000, Jeff Roberson wrote: > > >>>>>On Sun, 4 May 2008, Kostik Belousov wrote: > > >>>>> > > >>>>>>Since the review for the clone-at-open patch (fdclone) posted som= e=20 > > >>>>>>time > > >>>>>>ago > > >>>>>>mostly says that it would be better to implement per-file private= data > > >>>>>>instead, I produced the patch along this line, > > >>>>>> > > >>>>>>The patch does not change the cdevsw ABI, instead, three new func= tions > > >>>>>>nt devfs_get_cdevpriv(void **datap); > > >>>>>>int devfs_set_cdevpriv(void *priv, cdevpriv_dtr_t dtr); > > >>>>>>void devfs_clear_cdevpriv(void); > > >>>>>>are provided for manipulation of the per-file private data. > > >>>>>> > > >>>>>>devfs_set_cdevpriv assigns the priv as private data for the file > > >>>>>>descriptor > > >>>>>>which is used to initiate currently performed driver operation. d= tr > > >>>>>>is the function that will be called when either the last refernce= to > > >>>>>>the file goes away or devfs_clear_cdevpriv is called. > > >>>>>> > > >>>>>>devfs_get_cdevpriv is the obvious accessor. > > >>>>>> > > >>>>>>devfs_clear_cdevpriv allows to clear the private data for the sti= ll > > >>>>>>open file. > > >>>>>> > > >>>>>>The synchronization of the cdev data and file private data is left > > >>>>>>to the driver code, I did not found any generic helper mechanism = that > > >>>>>>could be useful there. > > >>>>>> > > >>>>>>Patch: > > >>>>>>http://people.freebsd.org/~kib/misc/fdpriv.1.patch > > >>>>>> > > >>>>>>Dumb driver that shows the basic usage of the proposed KPI: > > >>>>>>http://people.freebsd.org/~kib/misc/fpclone.c > > >>>>>> > > >>>>>>Previous version of the patch was tested by Peter Holm. > > >>>>>> > > >>>>> > > >>>>>Hi Kostik, > > >>>>> > > >>>>>Are these per-instances structures intended to be used by anything= =20 > > >>>>>other > > >>>>>than devices? If not can we make them a union with the DTYPE_VNODE > > >>>>>fields to save space? > > >>>>> > > >>>>>Thanks, > > >>>>>Jeff > > >>>> > > >>>>The current version of the patch is at > > >>>>http://people.freebsd.org/~kib/misc/fdpriv.3.patch > > >>>> > > >>>>Per insistence of John Baldwin and request of Eric Anholt, the=20 > > >>>>destructors > > >>>>are called now when either file is last closed, or the device is > > >>>>destroyed. > > >>>>This versions adds only one pointer to the struct file. > > >>>> > > >>>>Jeff, would you, please, explicitely specify what field you propose= to > > >>>>union with the f_cdevpriv ? > > >> > > >>f_nextoff and f_seqcount are only used if vn_read() and vn_write() are > > >>used. They do not apply to any other descriptors. > > >I use the f_cdevpriv !=3D NULL as an indicator for the necessity to en= ter > > >the cdevpriv code, in particular, locking the cdevpriv_mtx, that would > > >otherwise needed to be entered at each last close. I think that one > > >pointer for the struct file is not too big cost, do you agree ? > >=20 > > No, it's not a big cost, however if it is possible to avoid that is bes= t. > >=20 > > Can you not check the type before checking f_cdevpriv? Should we not o= nly=20 > > be checking cdevpriv in contexts where we know that it is not a vnode? >=20 > I am sorry, my english may be not enough, so I may interpret your > proposal mistakenly. I read it as a suggestion to check the file type > before accessing the f_cdevpriv. >=20 > The problem with the f_cdevpriv exists only at the _fdrop(). There, we > have a file of f_type =3D=3D DTYPE_VNODE both for devfs and normal files. > I cannot check the f_vnode since the vnode may be reclaimed. The only > differentiator is the f_ops, that is devfs_ops_f for devfs file, and > vnops for the normal file during the file lifetime. Unfortunately, > f_ops is reset to the badfileops by vn_closefile before the _fdrop() is > getting called. >=20 > Reserving the flag in the f_flag looks not good due to interaction with > the userspace. >=20 > I do not want the callback to be called before the d_close() driver method > gets a chance to clean the data. So, I cannot implement overlay of the cdevpriv over the seqaccess data=20 without some additional flag. On the other hand, use of 2 bytes for the f_type is overkill when the range of the types is [1,8]. I divided it to two one-byte fields, and new field is used for filetype-specific flags. http://people.freebsd.org/~kib/misc/fdpriv.4.patch shall give the same size of the struct file while not causing unconditional acquire of the cdevpriv_mtx on the last file close. Jeff, do you agree with the proposed vivisection of the f_type ? I will ask Peter to retest the patch then. --5glgGqCv79Y86mRH Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkgqsaYACgkQC3+MBN1Mb4hPJQCgnwivOryzU6WwVdASNvY0MNXb UT8AoOL6Cg7J3i0Ro3xNTMYtszAVFpvd =AbHK -----END PGP SIGNATURE----- --5glgGqCv79Y86mRH--