If there is an error on a partially completed bio it's uptodate bit is cleared and an error value is retured, but DM will see that bi_size is not yet zero and ignore it. SCSI will fail the rest of the IO if the fail fast bit is set, so DM multipath will eventually see the error from them. However, if that behavior is not a requirement the patch below would be needed to detect errors in bios where the begining is not uptodate but the end completed without errors. SCSI will not always fail the rest of the IO when the fail fast bit is not set, so this may be a bug in dm-crypt and dm-raid1. Mike Christie --- linux-2.6.4-rc1-udm1.orig/drivers/md/dm-mpath.c 2004-03-03 19:56:43.000000000 -0800 +++ linux-2.6.4-rc1-udm1/drivers/md/dm-mpath.c 2004-03-03 19:52:55.000000000 -0800 @@ -551,8 +551,9 @@ static int do_end_io(struct multipath *m int error, struct mpath_io *io) { int r; + int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); - if (error) { + if (uptodate) { spin_lock(&m->lock); if (!m->nr_valid_paths) { spin_unlock(&m->lock);