linux-kernel - [PATCH 16/38] drbd: add comment why we want to first call local-io-error, then send state

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Date:	Wed, 25 Nov 2015 11:53:49 +0100
From:	Philipp Reisner <philipp.reisner@...bit.com>
To:	Jens Axboe <axboe@...com>, linux-kernel@...r.kernel.org
Cc:	drbd-dev@...ts.linbit.com
Subject: [PATCH 16/38] drbd: add comment why we want to first call local-io-error, then send state

From: Lars Ellenberg <lars.ellenberg@...bit.com>

Even though we really want to get the state information about our bad
disk to the peer as soon as possible, it is useful to first call the
local-io-error handler.

People may chose to hard-reset the box from there.
If that looks and behaves exactly like a "regular node crash", without
bumping the data generation UUIDs on the peer in between, it makes it
easier to deal with.

If you intend to return from the local-io-error handler, then better
return as quickly as possible to avoid triggering other timeouts.

Signed-off-by: Philipp Reisner <philipp.reisner@...bit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@...bit.com>
---
 drivers/block/drbd/drbd_state.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
index 06afd4d..a4e4505 100644
--- a/drivers/block/drbd/drbd_state.c
+++ b/drivers/block/drbd/drbd_state.c
@@ -1859,6 +1859,10 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
 
 			was_io_error = test_and_clear_bit(WAS_IO_ERROR, &device->flags);
 
+			/* Intentionally call this handler first, before drbd_send_state().
+			 * See: 2932204 drbd: call local-io-error handler early
+			 * People may chose to hard-reset the box from this handler.
+			 * It is useful if this looks like a "regular node crash". */
 			if (was_io_error && eh == EP_CALL_HELPER)
 				drbd_khelper(device, "local-io-error");
 
-- 
1.9.1

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