Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 19 Oct 2001 11:58:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 19 Oct 2001 11:58:35 -0400 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:35599 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id ; Fri, 19 Oct 2001 11:58:26 -0400 To: linux-kernel@vger.kernel.org From: torvalds@transmeta.com (Linus Torvalds) Subject: Re: Poor floppy performance in kernel 2.4.10 Date: Fri, 19 Oct 2001 15:57:40 +0000 (UTC) Organization: Transmeta Corporation Message-ID: <9qpihk$23p$1@penguin.transmeta.com> In-Reply-To: <20011018194415.S12055@athlon.random> X-Trace: palladium.transmeta.com 1003507109 4721 127.0.0.1 (19 Oct 2001 15:58:29 GMT) X-Complaints-To: news@transmeta.com NNTP-Posting-Date: 19 Oct 2001 15:58:29 GMT Cache-Post-Path: palladium.transmeta.com!unknown@penguin.transmeta.com X-Cache: nntpcache 2.4.0b5 (see http://www.nntpcache.org/) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org In article , Giuliano Pochini wrote: > >> Indeed, only 2.2 trusted the check media change information and left the >> cache valid on top of the floppy across close/open of the blkdev. > >Which is not a bad thing IMHO, but it can cause problems with >some broken SCSI implementation where the drive doesn't send >UNIT_ATTENTION after a media change (like my MO drive when I >misconfigured the jumpers, damn :-((( ). Well, the original reason to not trust the media-change signal is that some floppy drives simply do not implement the signal at all. Don't ask me why. So a loong time ago Linux had the problem that when you changed floppies you wouldn't see the new information - or you'd see _partially_ new and old information depending on what your access patterns were and what the caches contained. So it's pretty much across the board - broken SCSI, broken floppies, just about any changeable media tends to have _some_ bad cases. And with the floppy case, there was no way to notice at run-time whether the unit was broken or not - the floppy drives have no ID's to blacklist etc. So either you tell people to flush their caches by hand (which we did), or you just always flush it between separate opens (which we later did). Linus - 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/