Date: Fri, 25 Nov 2011 12:02:35 +0100 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-fs@freebsd.org Subject: Re: Does UFS2 send BIO_FLUSH to GEOM when update metadata (with softupdates)? Message-ID: <20111125110235.GB1642@garage.freebsd.pl> In-Reply-To: <20111123194444.GE50300@deviant.kiev.zoral.com.ua> References: <1957615267.20111123230026@serebryakov.spb.ru> <20111123194444.GE50300@deviant.kiev.zoral.com.ua>
next in thread | previous in thread | raw e-mail | index | archive | help
--OwLcNYc0lM97+oe1 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Nov 23, 2011 at 09:44:44PM +0200, Kostik Belousov wrote: > On Wed, Nov 23, 2011 at 11:00:26PM +0400, Lev Serebryakov wrote: > > Hello, Freebsd-fs. > >=20 > > Does UFS2 with softupdates (without journal) issues BIO_FLUSH to > > GEOM layer when it need to ensure consistency on on-disk metadata? > No. Softupdates do not need flushes. Well, they do for two reasons: 1. To properly handle sync operations (fsync(2), O_SYNC). 2. To maintain consistent on-disk structures. The second point is there, because BIO_FLUSH is the only way to avoid reordering (apart from turning off disk write cache). SU assumes no I/O reordering will happen, which is very weak assumption. --=20 Pawel Jakub Dawidek http://www.wheelsystems.com FreeBSD committer http://www.FreeBSD.org Am I Evil? Yes, I Am! http://yomoli.com --OwLcNYc0lM97+oe1 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.14 (FreeBSD) iEYEARECAAYFAk7PdcsACgkQForvXbEpPzR8WgCffIE47sDfnjN+O411ELBT/hAV NRcAoKzWvT5wiAqg6reIdvqJqtAq5/30 =kLyd -----END PGP SIGNATURE----- --OwLcNYc0lM97+oe1--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20111125110235.GB1642>