From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yh0-f42.google.com ([209.85.213.42]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Wk2aq-0005KO-Qc for linux-mtd@lists.infradead.org; Tue, 13 May 2014 02:37:25 +0000 Received: by mail-yh0-f42.google.com with SMTP id t59so7236369yho.1 for ; Mon, 12 May 2014 19:36:57 -0700 (PDT) Date: Mon, 12 May 2014 19:36:51 -0700 From: Brian Norris To: Ezequiel Garcia Subject: Re: [PATCH 2/4] mtd: nand: Account the blocks used by the BBT in the ecc_stats Message-ID: <20140513023651.GC28907@ld-irv-0074> References: <1395403064-28113-1-git-send-email-ezequiel.garcia@free-electrons.com> <1395403064-28113-3-git-send-email-ezequiel.garcia@free-electrons.com> <20140513022753.GB1447@arch.cereza> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140513022753.GB1447@arch.cereza> Cc: David Woodhouse , linux-mtd@lists.infradead.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, May 12, 2014 at 11:27:53PM -0300, Ezequiel Garcia wrote: > On 21 Mar 08:57 AM, Ezequiel Garcia wrote: > > Strictly speaking we should be updating the ecc_stats in the master > > MTD object, with the blocks used by the bad block table. > > > > This is already being done for bad and reserved blocks detected doing > > the BBT search, but not for the blocks used by the BBT itself. This commit > > adds the latter. > > > > It should be noted that the ecc_stats structure is kept only for userspace > > information, accesible through an ioctl. However, since the master MTD object > > is not tied to any /dev/mtd{N} device node in the filesystem, there's currently > > no way to retrieve this information. > > > > This ecc_stats is used for the MTD partitions typically allocated and > > registered by mtd_device_parse_register(). These have a device node, but scan > > for bad blocks and updates the ecc_stats in a different code path. > > > > Signed-off-by: Ezequiel Garcia > > -- > > For the reasons exposed above, it's not clear we should remove the ecc_stats > > update in the master MTD altogether or simply take account of the BBT blocks > > for consistency. I've chosen the latter, for it seemed a safer changer. > > > > I'm open to discussion, though. > > Brian, > > Can you comment a bit on this one? Should I keep this change in v2? I'm not really sure. I'm honestly having a hard time tracking all the potentially-configurable knobs of nand_bbt.c. It looks like only diskonchip sets a reserved_block_code, so some of the existing code isn't really even tested widely. And like you mention, the ecc_stats from the master MTD are not propagated directly to the partition (nor should they be), so the stat is really unused. I'm not 100% confident that we won't double-count any 'bbtblocks' in your current patch. Maybe we should rewrite some of this stuff... I'll look at this again when my eyes are fresh. Brian