From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: quick question about write-intent bitmap Date: Thu, 1 Dec 2011 18:18:52 +1100 Message-ID: <20111201181852.5810ba4c@notabene.brown> References: Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/W0Dr52oqlWS/L9gmNF_qq6i"; protocol="application/pgp-signature" Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Marcus Sorensen Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/W0Dr52oqlWS/L9gmNF_qq6i Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 30 Nov 2011 23:34:13 -0700 Marcus Sorensen wrote: > I would appreciate being pointed to any sort of in-depth documentation > on how the write intent bitmap works. To make my question quick, I'm > wondering how the write-intent bitmap holds up to writeback caching. > It seems like md would assume that the cached writes had made it to > disk, and only rebuild writes that happened since the disk was > removed, leaving an inconsistent array. > md writes bitmaps with REQ_WRITE | REQ_SYNC | REQ_FLUSH | REQ_FUA If that returns before the data is truly safe, then you have a bug somewher= e. i.e. md tries to write-through an cache that might be in the way. NeilBrown --Sig_/W0Dr52oqlWS/L9gmNF_qq6i Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBTtcqXDnsnt1WYoG5AQLZdxAAvupogKUg/VwEguUbwOSWCJ+/K7cQ3AYa B1I3dEzQvm93D8RSjugSPVHhRZszm3uHWOZsGXFqeY79jwNY9unVH4xzFL1OWUKc lmVJJzT4RuUhx+IeyoewIY/MO9934QGLXMQsl9Z4uyvJxxl1xPcjmPauoDhkRu9y dSviLdYKrqDKZEyObmBBCcjwC+zuamUHzCaLt/+NqGoH76TWZPAAKuH4Ca5uGo+C oPike9ay9YxGfRGHyO9t+1W/Ge6s8ZoYtNM9Wa2jZj9s40qbH9qRhqdzB2JsZaS7 w6oKrWM9B5uGyx/mYE+OpE9udWb22hHMLx3TDbgWC8r2tTKzVAtB60fwdwfpQGej v9+o/wzyTC7hO1E6wLTH97SP+naVrjnoiQRKSztoXKIInHzUJS059CrF9z1wqZjj XCUJijgv8fTqmQ8O05M8P+ijTDbL3jVYeeCEyetH2rxVfUXVQvvFsuklvE4lCkvr SD69bE3/b/duxniCWxOYM8eITioYnODcX9ZtlGPQjVSyuIIJrLCKDCydPnl+flB3 8vf68XOFwdtzjXwLV+x3+P4y02R4TQfvJZ6dVWc3OFrH2/Bq1c4MLI+5COcNdSf3 FxzBT8T+S9EgHpX1xx/O+qsZKwbAbvyK3O/GfJSnMNVAP7ASjZMSn0/EzHRbtUeE Wo83fcoouvg= =3B+k -----END PGP SIGNATURE----- --Sig_/W0Dr52oqlWS/L9gmNF_qq6i--