From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: mini change of raid5.c Date: Thu, 10 Nov 2011 09:15:47 +1100 Message-ID: <20111110091547.19b96e9b@notabene.brown> References: <4EBA5E5D0200004000001B21@ptbl-mail.dnsalias.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/r/4w6juTea.s97GO3pgNgUd"; protocol="application/pgp-signature" Return-path: In-Reply-To: <4EBA5E5D0200004000001B21@ptbl-mail.dnsalias.net> Sender: linux-raid-owner@vger.kernel.org To: Hardy Flor Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/r/4w6juTea.s97GO3pgNgUd Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 09 Nov 2011 11:05:01 +0100 "Hardy Flor" wrote: > Hello Mr Brown, >=20 > can you please transmit this small change to the file raid5.c? There is > thus a rapid repair of a raid6 possible, using only the defective areas > must be checked. This change writes only the error position in the log > during the function "check". >=20 > Kind regards >=20 > Hardy Flor Hi Hardy, thanks for suggesting that change. There a couple of problems with it that would need to be fixed though. Firstly, it print the 'Q' block for RAID5. However there is no Q block for RAID5 so that is just distracting noise which is easy to remove. Secondly - and more significantly - if you create a new RAID6 array with th= is patch, you can expect every stripe to have incorrect parity, so you will get a message for every single stripe which would not be good. I don't really think that printk is the best way to get useful data from the kernel. I would prefer that raid5 kept a list of sectors internally and ma= de them available through a file in sysfs. e.g. ..../md/mismatch_list. You could then enhance raid6check.c (part of 'mdadm') to read that file and explain exactly what is happening at each offset. We would need to limit the number of addresses reported. If we just allocated one page and treated it as an array of 256 64bit numbers that wou= ld probably be sufficient. Would you like to try coding that approach? Thanks, NeilBrown --Sig_/r/4w6juTea.s97GO3pgNgUd Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQIVAwUBTrr7kznsnt1WYoG5AQImSA/8DKRT6mOzwsozTTRr33WHD2NbQEPCDJ9m fX4Kq47yh3KwAm473jB0EdxSAc6JFsz1GrhfwiZMMQbcYhJInZcp4Mv2WLhdnVlb RiDGlwYXk+T1IXHBz+Y8a4+sP8L8XNi2O/bqKlIjFzPA7yu+NdQXxpggI8YyPFrU 861wDpYtVz+PL7nlsxrUExCosxvQEzaaNDJ+j0K8dm4Y+ZVd1zvYZDqHtokaOZSe HjM6vbRXvutO3dfBdoTteyixe2YclX3d7eHgvdxJQpSUsIR5K9GTWpbiFvmkdeUY 2SCJQnoduzOdhr1wwXFU1W4Wa2OJmqYIcov7vgv7ILoxXwUdoV2FjH5+Jp0v/wsn mL1ZeL0uo6Qad5BPlj6JDs35/GEoEzBVoX1ebzjquIHkPMkZ4ahNbWBC0dFgfYAy 6J8SCP1izYmUZ1ixgjqqE/zOpcdgt6INo7PY86n9nqlh2TV0Ag+s7sugg+k8t2Ok 4EywbiSLmyGxl7jdoTTSWdjPF1akeZAahtPOczAeCGODXoQEKQYtXL59qbu56Axo 9EdSbl7zqZAzEPQS9C/Trg60Y7sJPsOMpfba7H1mu9iDYr1U2Ii4y1SQwCiJADMp EPkiXMkz09ffBHGn+d647pE4knFpb/UVew806VmNtfDx4e5UcQw1wlbDlS5RkpWl E7mtkxVdqD0= =uh3L -----END PGP SIGNATURE----- --Sig_/r/4w6juTea.s97GO3pgNgUd--