Date: Fri, 24 Jun 2011 11:38:41 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: freebsd-fs@freebsd.org, Robert Watson <rwatson@freebsd.org>, Garance A Drosehn <gad@freebsd.org> Subject: Re: [rfc] 64-bit inode numbers Message-ID: <20110624083841.GV48734@deviant.kiev.zoral.com.ua> In-Reply-To: <1437987696.1010265.1308875030014.JavaMail.root@erie.cs.uoguelph.ca> References: <20110623222630.GU48734@deviant.kiev.zoral.com.ua> <1437987696.1010265.1308875030014.JavaMail.root@erie.cs.uoguelph.ca>
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--Xm1wk/WBwRlpvc4I Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jun 23, 2011 at 08:23:50PM -0400, Rick Macklem wrote: > Kostik Belousov wrote: > > On Thu, Jun 23, 2011 at 06:05:56PM -0400, Garance A Drosehn wrote: > > > On 6/23/11 4:11 AM, Kostik Belousov wrote: > > > >On Thu, Jun 23, 2011 at 09:43:33AM +0300, Gleb Kurtsou wrote: > > > > > > > >>On (22/06/2011 19:19), Garance A Drosehn wrote: > > > >> > > > >>>Sorry for replying to an older message, but a reply made in a > > > >>>different > > > >>>thread reminded me about this project... > > > >>> > > > >>>Also, I may have asked this before. In fact, I'm almost sure that > > > >>>I > > > >>>started > > > >>>a reply to this back in Jan/Feb, but my email client claims I > > > >>>never > > > >>>replied > > > >>>to this topic... > > > >>> > > > >>>Are you increasing only the size of ino_t, or could you also look > > > >>>at > > > >>>increasing the size of dev_t? (just curious...) > > > >>> > > > >>Sure. Incorporating as much of similar changes as possible is > > > >>good. > > > >>I've added Kostik and Matthew to CC list, it's for them to decide. > > > >> > > > >>dev_t on other OSes: > > > >> NetBSD - uint64_t > > > >> DragonFly - uint32_t > > > >> Darwin - __int32_t > > > >> OpenSolaris - ulong_t > > > >> Linux - __u32 > > > >> > > > >>Considering this I think 3rd party software is not ready for such > > > >>change. > > > >> > > > >>Major/minor mapping to dev_t will get more complicated. > > > >> > > > >>And the most important question: what would you want it for? [...] > > > >> > > > >Indeed, this is the right question. > > > > > > > Consider the thread "Increasing the size of dev_t and ino_t" from > > > freebsd-arch in 2002: > > > > > > http://docs.freebsd.org/mail/archive/2002/freebsd-arch/20020317.freeb= sd-arch.html > > > > > > In particular, this message by Robert Watson: > > > > > > http://docs.freebsd.org/cgi/getmsg.cgi?fetch=3D139853+0+archive/2002/= freebsd-arch/20020317.freebsd-arch > > > > > > I just participated in an online conference for OpenAFS, and while > > > it > > > isn't exactly taking the world by storm, I keep thinking it would be > > > useful if FreeBSD could map individual AFS volumes to unique dev_t > > > identifiers. And given the way AFS is implemented (as a global > > > filesystem > > > with many cells all reachable at the same time), and given the way > > > most > > > sites deploy AFS (with thousands or tens-of-thousands of individual > > > AFS > > > volumes *per site*), that adds up to a lot of values for dev_t. > > > > > > The upcoming release of OpenAFS should include a working and pretty > > > stable AFS client for FreeBSD, so having a larger dev_t would have a > > > more immediate application than it did back in 2002. > > Am I right that the issue is the uniqueness of the dev_t for each > > AFS volume, as reported by stat(2) ? > >=20 > > Shouldn't the AFS client synthesize the dev_t for each new volume > > mounted ? It seems that the current 32bit dev_t would be enough, > > since I do not expect to see hundreds of thousands of mounts > > on an single system. > >=20 > I think the main concern is making sure that the value is not the > same as what another mount already has. That's why mnt_stat.f_fsid > is synthesized for NFS, I think? We have quite useful unit number allocator that guarantees uniqueness, see sys/systm.h, look for unrhdr. In fact, it is used by devfs to maintain dev_t values, see struct cdev_priv member cdp_inode, which value typically ends up in the st_dev. If needed, the devfs inode allocator can be exported. >=20 > > Please note that we do not guarantee dev_t stability across reboots > > even > > for real devices. --Xm1wk/WBwRlpvc4I Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iEYEARECAAYFAk4ETRAACgkQC3+MBN1Mb4gS7ACg6DqqPm+BjxLGEZolpPPtXuSZ XswAnRrAHE9tlv8hUt/eHWRCLDMGQrfM =S+AK -----END PGP SIGNATURE----- --Xm1wk/WBwRlpvc4I--
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