From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Mamedov Subject: Re: [md PATCH 01/10] md: allow a reshape operation to be reversed. Date: Mon, 1 Oct 2012 15:11:28 +0600 Message-ID: <20121001151128.0a5e336f@natsu> References: <20120403054656.19495.36380.stgit@notabene.brown> <20120403055301.19495.37242.stgit@notabene.brown> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/WTdHKq=eyqPnx2XZ0sv1wty"; protocol="application/pgp-signature" Return-path: In-Reply-To: <20120403055301.19495.37242.stgit@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/WTdHKq=eyqPnx2XZ0sv1wty Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Tue, 03 Apr 2012 15:53:01 +1000 NeilBrown wrote: > Currently a reshape operation always progresses from the start > of the array to the end unless the number of devices is being > reduced, in which case it progressed in the opposite direction. >=20 > To reverse a partial reshape which changes the number of devices > you can stop the array and re-assemble with the raid-disks numbers > reversed and it will undo. >=20 > However for a reshape that does not change the number of devices > it is not possible to reverse the reshape in the middle - you have to > wait until it completes. >=20 > So add a 'reshape_direction' attribute with is either 'forwards' or > 'backwards' and can be explicitly set when delta_disks is zero. >=20 > This will become more important when we allow the data_offset to > change in a reshape. Then the explicit statement of what direction is > being used will be more useful. >=20 > This can be enabled in raid5 trivially as it already supports > reverse reshape and just needs to use a different trigger to request it. Hello, Is it possible to use this to cancel a RAID5 reshape that is reducing the number of devices? I understand that reshape goes backwards by design in this case, so I need = to switch it to "forwards". I stopped the reshaping array and then started it with "mdadm --assemble --freeze-reshape" and listing the backup file and all the devices on the co= mmand line. But even then: # echo forwards > /sys/block/md0/md/reshape_direction=20 -bash: echo: write error: Device or resource busy --=20 With respect, Roman ~~~~~~~~~~~~~~~~~~~~~~~~~~~ "Stallman had a printer, with code he could not see. So he began to tinker, and set the software free." --Sig_/WTdHKq=eyqPnx2XZ0sv1wty Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAlBpXkAACgkQTLKSvz+PZwha0QCggxaajfyrFiO0+xgdRPyxIlKK nhEAmwS+2983JpxU92uWuX0TkKoGHn5+ =UBFn -----END PGP SIGNATURE----- --Sig_/WTdHKq=eyqPnx2XZ0sv1wty--