From mboxrd@z Thu Jan 1 00:00:00 1970 From: Namhyung Kim Subject: Re: [md PATCH 01/36] md: beginnings of bad block management. Date: Tue, 26 Jul 2011 14:17:12 +0900 Message-ID: <1311657432.1522.2.camel@leonhard> References: <20110721024556.8422.99443.stgit@notabene.brown> <20110721025847.8422.29443.stgit@notabene.brown> <878vrq5pda.fsf@gmail.com> <20110726122627.5288a3ff@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20110726122627.5288a3ff@notabene.brown> Sender: linux-raid-owner@vger.kernel.org To: NeilBrown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids 2011-07-26 (=ED=99=94), 12:26 +1000, NeilBrown: > On Sat, 23 Jul 2011 00:03:45 +0900 Namhyung Kim = wrote: >=20 > > NeilBrown writes: > >=20 > > > This the first step in allowing md to track bad-blocks per-device= so > > > that we can fail individual blocks rather than the whole device. > > > > > > This patch just adds a data structure for recording bad blocks, w= ith > > > routines to add, remove, search the list. > > > > > > Signed-off-by: NeilBrown > > > --- > > > > > > drivers/md/md.c | 457 +++++++++++++++++++++++++++++++++++++++++= ++++++++++++++ > > > drivers/md/md.h | 49 ++++++ > > > 2 files changed, 502 insertions(+), 4 deletions(-) > > > > > > + > > > +/* Bad block management. > > > + * We can record which blocks on each device are 'bad' and so ju= st > > > + * fail those blocks, or that stripe, rather than the whole devi= ce. > > > + * Entries in the bad-block table are 64bits wide. This compris= es: > > > + * Length of bad-range, in sectors: 0-511 for lengths 1-512 > > > + * Start of bad-range, sector offset, 54 bits (allows 8 exbibyte= s) > > > + * A 'shift' can be set so that larger blocks are tracked and > > > + * consequently larger devices can be covered. > > > + * 'Acknowledged' flag - 1 bit. - the most significant bit. > > > + */ > > > +/* Locking of the bad-block table is a two-layer affair. > > > + * Read access through ->active_page only requires an rcu_readlo= ck. > > > + * However if ->active_page is found to be NULL, the table > > > + * should be accessed through ->page which requires an irq-spinl= ock. > > > + * Updating the page requires setting ->active_page to NULL, > > > + * synchronising with rcu, then updating ->page under the same > > > + * irq-spinlock. > > > + * We always set or clear bad blocks from process context, but > > > + * might look-up bad blocks from interrupt/bh context. > > > + * > >=20 > > Empty line. > >=20 > > If the locking is complex, it'd be better defining separate functio= ns to > > deal with it, IMHO. Please see below. >=20 > I too have been feeling uncomfortable about the locking and I recentl= y > realised that I really should be using a seqlock rather than trying t= o force > RCU into the mould. So I have changed it and it is much better now. = Below > is new version. >=20 >=20 > > > +EXPORT_SYMBOL_GPL(rdev_set_badblocks); > >=20 > > I think it would be better if all exported functions in md.c have > > prefixed 'md_'. > >=20 >=20 > Probably good advice. I don't think I'll change it now but maybe in = a > subsequent patch so that I change them all at once. >=20 > Thanks, > NeilBrown >=20 > commit 0980048be17a45ae9e181ad04a549c31a499dee9 > Author: NeilBrown > Date: Tue Jul 26 12:22:08 2011 +1000 >=20 > md: beginnings of bad block management. > =20 > This the first step in allowing md to track bad-blocks per-device= so > that we can fail individual blocks rather than the whole device. > =20 > This patch just adds a data structure for recording bad blocks, w= ith > routines to add, remove, search the list. > =20 > Signed-off-by: NeilBrown with your another badblocks.page fix: Reviewed-by: Namhyung Kim --=20 Regards, Namhyung Kim -- 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