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Subject[PATCH 14/16] drbd: fix schedule in atomic
Date
From: Lars Ellenberg <lars.ellenberg@linbit.com>

An administrative detach used to request a state change directly to D_DISKLESS,
first suspending IO to avoid the last put_ldev() occuring from an endio handler,
potentially in irq context.

This is not enough on the receiving side (typically secondary), we may miss
some peer_req on the way to local disk, which then may do the last put_ldev()
from their drbd_peer_request_endio().

This patch makes the detach always go through the intermediate D_FAILED state.
We may consider to rename it D_DETACHING.

Alternative approach would be to create yet an other work item to be scheduled
on the worker, do the destructor work from there, and get the timing right.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
---
drivers/block/drbd/drbd_nl.c | 13 +++++++++----
1 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 019f762..414503a 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1706,12 +1706,17 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
static int adm_detach(struct drbd_conf *mdev)
{
enum drbd_ret_code retcode;
+ int ret;
drbd_suspend_io(mdev); /* so no-one is stuck in drbd_al_begin_io */
- retcode = drbd_request_state(mdev, NS(disk, D_DISKLESS));
- wait_event(mdev->misc_wait,
- mdev->state.disk != D_DISKLESS ||
- !atomic_read(&mdev->local_cnt));
+ retcode = drbd_request_state(mdev, NS(disk, D_FAILED));
+ /* D_FAILED will transition to DISKLESS. */
+ ret = wait_event_interruptible(mdev->misc_wait,
+ mdev->state.disk != D_FAILED);
drbd_resume_io(mdev);
+ if (retcode == SS_IS_DISKLESS)
+ retcode = SS_NOTHING_TO_DO;
+ if (ret)
+ retcode = ERR_INTR;
return retcode;
}

--
1.7.4.1


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