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? 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 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
