On Tue, Feb 26 2008 Jens Axboe wrote: > 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 <anders.henke@xxxxxxxx> 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? No, it doesn't. I've applied your patch manually, as 2.6.24.2. doesn't have a "blk-barrier.c": ---cut --- linux-2.6.24.2/block/ll_rw_blk.c.prepatch 2008-02-11 06:51:11.000000000 +0100 +++ linux-2.6.24.2/block/ll_rw_blk.c 2008-02-26 20:02:28.514641620 +0100 @@ -2667,8 +2667,11 @@ 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); } ---cut ... and the resulting kernel shows exactly the same behaviour than before: [ 752.301388] drbd0: Writing meta data super block now. [ 752.349713] drbd0: local disk flush failed with status -5 [ 752.416256] drbd0: local disk flush failed with status -5 [ 753.419254] drbd0: local disk flush failed with status -5 [ 753.925726] drbd0: local disk flush failed with status -5 [ 754.551176] drbd0: local disk flush failed with status -5 [ 754.806052] drbd0: local disk flush failed with status -5 [ 755.327988] drbd0: local disk flush failed with status -5 [ 755.781863] drbd0: local disk flush failed with status -5 [ 756.266694] drbd0: local disk flush failed with status -5 Anders > 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 > -- 1&1 Internet AG "Use the --force, Luke" Brauerstrasse 48 v://49.721.91374.50 D-76135 Karlsruhe f://49.721.91374.225 Amtsgericht Montabaur HRB 6484 Vorstand: Henning Ahlert, Ralph Dommermuth, Matthias Ehrlich, Andreas Gauger, Thomas Gottschlich, Matthias Greve, Robert Hoffmann, Markus Huhn, Achim Weiss Aufsichtsratsvorsitzender: Michael Scheeren -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
