Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758237AbZKXT4Q (ORCPT ); Tue, 24 Nov 2009 14:56:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758170AbZKXT4J (ORCPT ); Tue, 24 Nov 2009 14:56:09 -0500 Received: from cantor.suse.de ([195.135.220.2]:32972 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757361AbZKXT4H (ORCPT ); Tue, 24 Nov 2009 14:56:07 -0500 Date: Tue, 24 Nov 2009 20:56:08 +0100 From: Jan Kara To: Alan Stern Cc: Jan Kara , Boaz Harrosh , tmhikaru@gmail.com, Kernel development list , USB list , Jens Axboe , SCSI development list , linux-ext4@vger.kernel.org Subject: Re: Weird I/O errors with USB hard drive not remounting filesystem readonly Message-ID: <20091124195607.GC16662@quack.suse.cz> References: <4B0C1C20.2080901@panasas.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1158 Lines: 25 On Tue 24-11-09 14:28:35, Alan Stern wrote: > On Tue, 24 Nov 2009, Jan Kara wrote: > > > My naive guess would be that those non-retried reads were actually > > readahead. That's not retried if I remember correctly. Later, when we > > really needed the data, we sent another read request... > > That would be my guess too. I don't know how to verify it, though. > > If you're interested in pursuing this farther, I can show you how to > generate equivalent errors on demand using an emulated USB drive. > At this point it's not clear how much more one could learn by doing > this, however. After digging in block layer code, it's as we suspected: In case of host error DID_ERROR (which is our case), scsi request is retried iff it is not a FAILFAST request which is set if bio is doing readahead... So this is explained and everything behaves as it should. Thanks everybody involved :). Honza -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/