linux-kernel - [PATCH] xen-blkback: Switch to closed state after releasing the backing device

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Message-Id: <20180829065214.23546-1-Valentin.Vidic@CARNet.hr>
Date:   Wed, 29 Aug 2018 08:52:14 +0200
From:   Valentin Vidic <Valentin.Vidic@...Net.hr>
To:     Roger Pau Monné <roger.pau@...rix.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Jens Axboe <axboe@...nel.dk>, xen-devel@...ts.xenproject.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Valentin Vidic <Valentin.Vidic@...Net.hr>,
        stable@...r.kernel.org
Subject: [PATCH] xen-blkback: Switch to closed state after releasing the backing device

Switching to closed state earlier can cause the block-drbd
script to fail with 'Device is held open by someone':

root: /etc/xen/scripts/block-drbd: remove XENBUS_PATH=backend/vbd/6/51712
kernel: [ 2222.278235] block drbd6: State change failed: Device is held open by someone
kernel: [ 2222.278304] block drbd6:   state = { cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate r----- }
kernel: [ 2222.278340] block drbd6:  wanted = { cs:Connected ro:Secondary/Secondary ds:UpToDate/UpToDate r----- }
root: /etc/xen/scripts/block-drbd: Writing backend/vbd/6/51712/hotplug-error /etc/xen/scripts/block-drbd failed; error detected. backend/vbd/6/51712/hotplug-status error to xenstore.
root: /etc/xen/scripts/block-drbd: /etc/xen/scripts/block-drbd failed; error detected.

Signed-off-by: Valentin Vidic <Valentin.Vidic@...Net.hr>
Cc: stable@...r.kernel.org
---
 drivers/block/xen-blkback/xenbus.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index a4bc74e72c39..43bddc996709 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -323,6 +323,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
 {
 	WARN_ON(xen_blkif_disconnect(blkif));
 	xen_vbd_free(&blkif->vbd);
+	xenbus_switch_state(blkif->be->dev, XenbusStateClosed);
 	kfree(blkif->be->mode);
 	kfree(blkif->be);

@@ -814,7 +815,6 @@ static void frontend_changed(struct xenbus_device *dev,

 	case XenbusStateClosed:
 		xen_blkif_disconnect(be->blkif);
-		xenbus_switch_state(dev, XenbusStateClosed);
 		if (xenbus_dev_is_online(dev))
 			break;
 		/* fall through */
-- 
2.18.0