Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758679AbYBZQRy (ORCPT ); Tue, 26 Feb 2008 11:17:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751378AbYBZQRr (ORCPT ); Tue, 26 Feb 2008 11:17:47 -0500 Received: from brick.kernel.dk ([87.55.233.238]:23039 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751107AbYBZQRq (ORCPT ); Tue, 26 Feb 2008 11:17:46 -0500 Date: Tue, 26 Feb 2008 17:17:42 +0100 From: Jens Axboe To: Andrew Morton , Anders Henke , device-mapper development , linux-kernel@vger.kernel.org Subject: Re: [dm-devel] Re: device mapper not reporting no-barrier-support? Message-ID: <20080226161741.GN6704@kernel.dk> References: <20080225132615.GA21990@1und1.de> <20080225152050.94788622.akpm@linux-foundation.org> <20080226013656.GE1788@agk.fab.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080226013656.GE1788@agk.fab.redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2841 Lines: 84 On Tue, Feb 26 2008, Alasdair G Kergon wrote: > On Mon, Feb 25, 2008 at 03:20:50PM -0800, Andrew Morton wrote: > > On Mon, 25 Feb 2008 14:26:15 +0100 Anders Henke wrote: > > > I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel > > > 2.6.24.2 with DRBD 8.2.5 on top of an LVM2 device (LV). > > > -LVM2/device mapper doesn't support write barriers > > That's right. > > > > -DRBD uses blkdev_issue_flush() to flush its metadata to disk. > > Which won't work if device-mapper is underneath. > > > > On a no-barrier-device, DRBD should receive EOPNOTSUPP, but > > > it really does receive an EIO. Promptly, DRBD gives the > > > error message "drbd0: local disk flush failed with status -5". > > > I've posted a lengty summary of my findings to > > > http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html > > > ... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and > > > BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in > > > 2.6.24.2 aparently does return EIO for blkdev_issue_flush. > > I'd say it's a DM bug. > > The dm code is unchanged, but look at the limited endio handling in > ll_rw_blk.c: > > static void bio_end_empty_barrier(struct bio *bio, int err) > { > if (err) > clear_bit(BIO_UPTODATE, &bio->bi_flags); > > complete(bio->bi_private); > } > > int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector) > { > ... > wait_for_completion(&wait); > if (error_sector) > *error_sector = bio->bi_sector; > ret = 0; > if (!bio_flagged(bio, BIO_UPTODATE)) > ret = -EIO; You are right, the return value got broken there. Does this make it return -EOPNOTSUPP properly for you? diff --git a/block/blk-barrier.c b/block/blk-barrier.c index 6901eed..55c5f1f 100644 --- a/block/blk-barrier.c +++ b/block/blk-barrier.c @@ -259,8 +259,11 @@ int blk_do_ordered(struct request_queue *q, struct request **rqp) static void bio_end_empty_barrier(struct bio *bio, int err) { - if (err) + if (err) { + if (err == -EOPNOTSUPP) + set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); clear_bit(BIO_UPTODATE, &bio->bi_flags); + } complete(bio->bi_private); } @@ -309,7 +312,9 @@ int blkdev_issue_flush(struct block_device *bdev, sector_t *error_sector) *error_sector = bio->bi_sector; ret = 0; - if (!bio_flagged(bio, BIO_UPTODATE)) + if (bio_flagged(bio, BIO_EOPNOTSUPP)) + ret = -EOPNOTSUPP; + else if (!bio_flagged(bio, BIO_UPTODATE)) ret = -EIO; bio_put(bio); -- Jens Axboe -- 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/