From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: Invalidating the pages read from a disk which md marks as faulty later Date: Thu, 19 Jan 2012 07:19:55 +1100 Message-ID: <20120119071955.03a3fe9d@notabene.brown> References: Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/50VqzFG69mCKYyQlqZuJdxe"; protocol="application/pgp-signature" Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Krishnakumar R Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/50VqzFG69mCKYyQlqZuJdxe Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 18 Jan 2012 20:11:38 +0530 Krishnakumar R wrote: > Hi, >=20 > Does md invalidate the pages in the page cache for data read (earlier) fr= om > the disk, which md finds faulty, lets say due to an I/O error ? > The assumption here is that since md found a disk to be faulty, the data > which was earlier read and cached can be considered invalid. Thoughts ? > I would assume that the pages would be backed by md device, hence is it > possible to figure out which pages were given out with data from an > underlying disk inorder to invalidate them ? >=20 > Sorry, but this doesn't make any sense. When you read from a disk, the disk drive itself does a CRC check to confirm the data is valid. It if isn't you don't get to see the data. If it is, w= hy would you want to invalidate it? If a device is "Faulty", that doesn't mean it has corrupted data. It means it has inaccessible on unchangeable data. Though I might have misunderstood you. If you think I have, please give a more detailed scenario of the situation that should be handled differently. In any case, once md has returned the data to the caller there is nothing it can do to "invalidate" it. NeilBrown --Sig_/50VqzFG69mCKYyQlqZuJdxe Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBTxcpaznsnt1WYoG5AQKLBw/+I3vxWI7LMmJykQyGH5wZmJfH0feeKWbW 1yO+BgLffaQqvlP7XsCr018kn2yS8eteYRPYtyy7kPtYIZp7jdTcaAc0nfrFMJ7v l+Yl2MyXtNzWnM503tf9fEZ9PJLPXK0Zp1n1isO77pYwgG0dviaT+OFXlG19DtFs 2tzmL+6tAObua6qBV4r1fVGuS73CFdPE47dGxyajwWQSVMJn4FPzmcBc8fbV9Fcu TWpBdWzBDqxZQjthwuXHNXw+fXS8JPG5pA7TTrVoDtW6upwuroSRJBVDx21CJmdv n6uWDR00zfFt8ON9/Wn2S3ojj0xCED3X4Qb9AhordkX+ef/Cfh72IO4O9hsGwXAg dhchKvU6MZroJW9sOKyUEeLv2d++5mYMqrtIUFQ36oFbN1D3WXE/99RuISczBUSX mm+tfJ55BO24BMnJxwX511W3QTqIIyDnls7hlh48SKKDYDHoz1wzujJHtry/ToLQ RdrXWJIbhQBEIpOmko7KthHiWlrWqkc5fi10aW546h22TsNI+/GfInW+oAPMbjyJ Z7TqdzOJUbhSszkSBK9TWm//C7GmUUYxn0SaTyHPKnz5vbO6/NO4UeVFS3SlEcq/ +69lSwvqS8/X0DuIEerFisNbCa2YD2IoS7/KpRJ+TdiO+WmbQ7tJiGt9UM1sEHGw Qejn7G1GEfg= =1YKg -----END PGP SIGNATURE----- --Sig_/50VqzFG69mCKYyQlqZuJdxe--