Date: Fri, 30 Jan 2009 22:30:33 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: Tim Kientzle <kientzle@freebsd.org> Cc: Poul-Henning Kamp <phk@phk.freebsd.dk>, "'current@FreeBSD.org'" <current@freebsd.org> Subject: Re: RFC: Change mtree nsec handling? Message-ID: <20090130203033.GB52415@deviant.kiev.zoral.com.ua> In-Reply-To: <49833352.3010208@freebsd.org> References: <30968.1233310214@critter.freebsd.dk> <49833352.3010208@freebsd.org>
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--mxv5cy4qt+RJ9ypb Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jan 30, 2009 at 09:05:22AM -0800, Tim Kientzle wrote: > Poul-Henning Kamp wrote: > >In message <49829D49.10306@freebsd.org>, Tim Kientzle writes: > > > >>mtree support and the mtree(8) program, I found > >>that mtree formats timestamps rather strangely. > >> > >>For example, a timestamp of 1233295862.000001 > >>(1233295682 seconds and 1000 nanoseconds) > >>will be printed like this by mtree: > >> time=3D1233295862.1000 > >>Unsurprisingly, the mtree parsing works the same > >>way in reverse. > > > >>@@ -258,6 +259,8 @@ > >> val =3D ep + 1; > >> ip->st_mtimespec.tv_nsec > >> =3D strtoul(val, &ep, 10); > >>+ for (i =3D ep - val; i < 9; ++i) > >>+ ip->st_mtimespec.tv_nsec *=3D 10; > > > > > >Why is this bit needed ? > > >=20 > This is the part that converts 1233295862.000001 into > 1000 nanoseconds (instead of 1 nanosecond). >=20 > Two reasons: > 1) Documentation. It's much easier to document > "decimal seconds" than "period followed nine digits > representing the number of nanoseconds past the whole > second." > 2) Interoperability. I originally noticed this testing > other mtree-producing code against our mtree implementation. > For example, since FreeBSD filesystems never (?) store Look at the vfs.timestamp_precision sysctl in sys/kern/vfs_subr.c > higher resolution than microseconds, there's really > no reason to write more than 6 digits after the decimal > point. It seems a tad naive to assume that everyone > will always write 9 digits. >=20 > I can leave this out for a cycle if there's real concern. > Fractional seconds occur so rarely on FreeBSD systems > (to my knowledge, the kernel never spontaneously generates > them so they can only be created by tools like touch that > explicitly call utimes()) that I didn't think this > would affect any real applications. >=20 > But if I'm wrong.... <shrug> >=20 > Tim > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" --mxv5cy4qt+RJ9ypb Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkmDY2kACgkQC3+MBN1Mb4jNRgCg27il8U7YkkoDwrKn++AzkjyB AVYAni0NYYRkZJIBO4F3o4Sc3jspkd+p =hpK9 -----END PGP SIGNATURE----- --mxv5cy4qt+RJ9ypb--
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