Date: Sun, 23 Sep 2012 08:43:07 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: freebsd-geom@freebsd.org Subject: Re: geli and BIO_FLUSH and/or BIO_ORDERED issue? Message-ID: <20120923064307.GK1454@garage.freebsd.pl> In-Reply-To: <20120923044828.GI19036@funkthat.com> References: <20120919040430.GF19036@funkthat.com> <20120922162025.GE1454@garage.freebsd.pl> <20120923044828.GI19036@funkthat.com>
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[-- Attachment #1 --] On Sat, Sep 22, 2012 at 09:48:28PM -0700, John-Mark Gurney wrote: > Pawel Jakub Dawidek wrote this message on Sat, Sep 22, 2012 at 18:20 +0200: > > On Tue, Sep 18, 2012 at 09:04:30PM -0700, John-Mark Gurney wrote: > > > I was looking at geli and I'm not sure if it's implementing BIO_FLUSH > > > and/or BIO_ORDERED properly... > > > > > > >From my understanding is the BIO_ORDERED is suppose to wait for the > > > previous _WRITES to complete before returning so that you can ensure > > > that data is on disk, i.e. _ORDERED is set on a BIO_FLUSH... > > > > > > BIO_ORDERED is handled by diskq_* code such that when you add an _ORDERED > > > command, all commands are put after it, but there doesn't appear to > > > be any code to ensure that an _ORDERED command waits for prevoius > > > pending commands to complete.. > > > > > > This is extra obvious in eli in that a _FLUSH is immediately dispatched, > > > even when there may be _WRITEs that haven't been finished encrypting and > > > sent down to the disk to get _FLUSHed... > > > > > > Any comments about this? > > > > Hmm, BIO_ORDERED was introduced pretty recently and GEOM classes were > > not updated to honour it, but it also seems to be to complex to handle > > in GEOM classes. I wonder if we could hold off new writes and wait for > > the in-progress writes in GEOM if we spot BIO_ORDERED request without > > the need to implement this logic in GEOM classes. > > Yeh. When I was looking at it, it definately seems like it should be > something that we provide a generic method of handling (as part of > bioq_*), since all the geom classes need to handle it... No, in most cases this is not a problem, because most of GEOM classes just pass all I/O requests without any reordering, so it is enough if the very last layer (eg. disk driver) handles BIO_ORDERED properly. I thought what you meant with GELI was that it can reorder writes, for which it needs more time with BIO_FLUSH requests that it handles immediately. -- Pawel Jakub Dawidek http://www.wheelsystems.com FreeBSD committer http://www.FreeBSD.org Am I Evil? Yes, I Am! http://tupytaj.pl [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) iEYEARECAAYFAlBer3oACgkQForvXbEpPzTCvgCgjF+b+eI1KhJpnn0SbHH1gcf9 x7gAn2kiLWpY09P1j+AwHleTxG5j2iy4 =74PA -----END PGP SIGNATURE-----help
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