Comment 66 for bug 1569925

Hypothesis,

Test (2) - The error is propagated to upper layers after X seconds.

In this case I'm testing:

$ sudo iscsiadm -m node -o show | grep node.session.timeo.replac
node.session.timeo.replacement_timeout = 60
node.session.timeo.replacement_timeout = 60

And same "locking" behavior is observed, but for a certain period of time. Now, shutdown procedure stayed locked for exact 60 seconds before allowing the machine to shutdown. This means that the systemd logic NEEDS either a clear shutdown, for the _netdev filesystems, OR the error to be propagated so the umount() can go on:

[ 17.612020] connection1:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4294894197, last ping 4294895448, now 4294896700
[ 17.644128] connection2:0: ping timeout of 5 secs expired, recv timeout 5, last rx 4294894204, last ping 4294895456, now 4294896708

<60 seconds>

[ 78.044264] sd 2:0:0:1: rejecting I/O to offline device
[ 78.045297] blk_update_request: I/O error, dev sdb, sector 0
[ 78.046315] sd 3:0:0:1: rejecting I/O to offline device
[ 78.046357] sd 2:0:0:1: rejecting I/O to offline device
[ 78.046363] blk_update_request: I/O error, dev sdb, sector 0
[ 78.046487] sd 2:0:0:1: rejecting I/O to offline device
[ 78.050117] blk_update_request: I/O error, dev sda, sector 20481074
[ 78.051219] XFS (sda1): metadata I/O error: block 0x1387c32 ("xlog_iodone") error 5 numblks 64
[ 78.052727] XFS (sda1): Log I/O Error Detected. Shutting down filesystem
[ 78.053901] XFS (sda1): Please umount the filesystem and rectify the problem(s)
[ 78.060723] sd 3:0:0:1: rejecting I/O to offline device
[ 78.061759] blk_update_request: I/O error, dev sda, sector 0

<error was propagated>
<filesystems can proceed with umount>

[ OK ] Unmounted /ext4.
[ OK ] Unmounted /xfs.
[ OK ] Stopped File System Check on /dev/disk/by-label/XFS.
[ OK ] Stopped File System Check on /dev/disk/by-label/EXT4.
[ OK ] Removed slice system-systemd\x2dfsck.slice.