From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eivind Sarto Subject: Re: raid1 data corruption during resync Date: Tue, 2 Sep 2014 15:07:26 -0700 Message-ID: <18B7DF88-26D1-44B8-8F72-2159A2DF868D@gmail.com> References: <20A5228D-DD63-4A6C-B2C6-B0C38996E636@gmail.com> Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Brassow Jonathan Cc: Eivind Sarto , NeilBrown , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Sep 2, 2014, at 12:24 PM, Brassow Jonathan wro= te: >=20 > On Aug 29, 2014, at 2:29 PM, Eivind Sarto wrote: >=20 >> I am seeing occasional data corruption during raid1 resync. >> Reviewing the raid1 code, I suspect that commit 79ef3a8aa1cb1523cc23= 1c9a90a278333c21f761 introduced a bug. >> Prior to this commit raise_barrier() used to wait for conf->nr_pendi= ng to become zero. It no longer does this. >> It is not easy to reproduce the corruption, so I wanted to ask about= the following potential fix while I am still testing it. >> Once I validate that the fix indeed works, I will post a proper patc= h. >> Do you have any feedback? >>=20 >> =97 drivers/md/raid1.c 2014-08-22 15:19:15.000000000 -0700 >> +++ /tmp/raid1.c 2014-08-29 12:07:51.000000000 -0700 >> @@ -851,7 +851,7 @@ static void raise_barrier(struct r1conf=20 >> * handling. >> */ >> wait_event_lock_irq(conf->wait_barrier, >> - !conf->array_frozen && >> + !conf->array_frozen && !conf->nr_pending && >> conf->barrier < RESYNC_DEPTH && >> (conf->start_next_window >=3D >> conf->next_resync + RESYNC_SECTORS), >=20 > This patch does not work - at least, it doesn't fix the issues I'm se= eing. My system hangs (in various places, like the resync thread) afte= r commit 79ef3a8. When testing this patch, I also added some code to d= m-raid.c to allow me to print-out some of the variables when I encounte= r a problem. After applying this patch and printing the variables, I s= ee: > Sep 2 14:04:15 bp-01 kernel: device-mapper: raid: start_next_window = =3D 12288 > Sep 2 14:04:15 bp-01 kernel: device-mapper: raid: current_window_req= uests =3D -46 > 5257 > Sep 2 14:04:15 bp-01 kernel: device-mapper: raid: next_window_reques= ts =3D -11562 > Sep 2 14:04:15 bp-01 kernel: device-mapper: raid: nr_pending =3D 0 > Sep 2 14:04:15 bp-01 kernel: device-mapper: raid: nr_waiting =3D 0 > Sep 2 14:04:15 bp-01 kernel: device-mapper: raid: nr_queued =3D 0 > Sep 2 14:04:15 bp-01 kernel: device-mapper: raid: barrier =3D 1 > Sep 2 14:04:15 bp-01 kernel: device-mapper: raid: array_frozen =3D 0 >=20 > Some of those values look pretty bizarre to me and suggest the accoun= ting is pretty messed up. >=20 > brassow >=20 After reviewing commit 79ef3a8aa1cb1523cc231c9a90a278333c21f761 I notic= e that wait_barrier() will now only exclude writes. User reads are not= excluded even if the fall within the resync window. The old implementation used to exclude both reads and writes while resy= nc-IO is active. Could this be a cause of data corruption? -eivind-- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html