drbd: fix potential deadlock on detach

If we have contention in drbd_al_begin_iod (heavy randon IO),
an administrative request to detach the disk may deadlock
for similar reasons as the recently fixed deadlock if detaching
because of IO-error.

The approach taken here is to either go through the intermediate
cleanup state D_FAILED, or first lock out application io,
don't just go directly to D_DISKLESS.

We need an additional state bit (WAS_IO_ERROR) to distinguish
the -> D_FAILED because of IO-error from other failures.

Sanitize D_ATTACHING -> D_FAILED to D_ATTACHING -> D_DISKLESS.
If only attaching, ldev may be missing still, but would be referenced
from within the after_state_ch for -> D_FAILED, potentially
dereferencing a NULL pointer.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 6ec922c623a1..04a823b01da5 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -3363,7 +3363,7 @@ static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
                 if (ns.conn == C_MASK) {
                         ns.conn = C_CONNECTED;
                         if (mdev->state.disk == D_NEGOTIATING) {
-                                drbd_force_state(mdev, NS(disk, D_DISKLESS));
+                                drbd_force_state(mdev, NS(disk, D_FAILED));
                         } else if (peer_state.disk == D_NEGOTIATING) {
                                 dev_err(DEV, "Disk attach process on the peer node was aborted.\n");
                                 peer_state.disk = D_DISKLESS;