From 6f5986bce558e64fe867bff600a2127a3cb0c006 Mon Sep 17 00:00:00 2001 From: Joe Jin <joe.jin@oracle.com> Date: Mon, 15 Aug 2011 12:51:31 +0800 Subject: [PATCH 1/2] xen-blkback: Don't disconnect backend until state switched to XenbusStateClosed. When do block-attach/block-detach test with below steps, umount hangs in the guest. Furthermore shutdown ends up being stuck when umounting file-systems. 1. start guest. 2. attach new block device by xm block-attach in Dom0. 3. mount new disk in guest. 4. execute xm block-detach to detach the block device in dom0 until timeout 5. Any request to the disk will hung. Root cause: This issue is caused when setting backend device's state to 'XenbusStateClosing', which sends to the frontend the XenbusStateClosing notification. When frontend receives the notification it tries to release the disk in blkfront_closing(), but at that moment the disk is still in use by guest, so frontend refuses to close. Specifically it sets the disk state to XenbusStateClosing and sends the notification to backend - when backend receives the event, it disconnects the vbd from real device, and sets the vbd device state to XenbusStateClosing. The backend disconnects the real device/file, and any IO requests to the disk in guest will end up in ether, leaving disk DEAD and set to XenbusStateClosing. When the guest wants to disconnect the disk, umount will hang on blkif_release()->xlvbd_release_gendisk() as it is unable to send any IO to the disk, which prevents clean system shutdown. Solution: Don't disconnect backend until frontend state switched to XenbusStateClosed. Signed-off-by: Joe Jin <joe.jin@oracle.com> Cc: Daniel Stodden <daniel.stodden@citrix.com> Cc: Jens Axboe <jaxboe@fusionio.com> Cc: Annie Li <annie.li@oracle.com> Cc: Ian Campbell <Ian.Campbell@eu.citrix.com> [v1: Modified description a bit] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> --- 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 6cc0db1bf522..7be3d0fe8ad3 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -601,11 +601,11 @@ static void frontend_changed(struct xenbus_device *dev, break; case XenbusStateClosing: - xen_blkif_disconnect(be->blkif); xenbus_switch_state(dev, XenbusStateClosing); break; case XenbusStateClosed: + xen_blkif_disconnect(be->blkif); xenbus_switch_state(dev, XenbusStateClosed); if (xenbus_dev_is_online(dev)) break; From 1bc05b0ae6448b20d46076899e0cc12ad999e50e Mon Sep 17 00:00:00 2001 From: Joe Jin <joe.jin@oracle.com> Date: Mon, 15 Aug 2011 12:57:07 +0800 Subject: [PATCH 2/2] xen-blkback: fixed indentation and comments This patch fixes belows: 1. Fix code style issue. 2. Fix incorrect functions name in comments. Signed-off-by: Joe Jin <joe.jin@oracle.com> Cc: Jens Axboe <jaxboe@fusionio.com> Cc: Ian Campbell <Ian.Campbell@eu.citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> --- drivers/block/xen-blkback/common.h | 2 +- drivers/block/xen-blkback/xenbus.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h index 9e40b283a468..00c57c90e2d6 100644 --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -46,7 +46,7 @@ #define DRV_PFX "xen-blkback:" #define DPRINTK(fmt, args...) \ - pr_debug(DRV_PFX "(%s:%d) " fmt ".\n", \ + pr_debug(DRV_PFX "(%s:%d) " fmt ".\n", \ __func__, __LINE__, ##args) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 7be3d0fe8ad3..a96cb5f893a8 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -590,7 +590,7 @@ static void frontend_changed(struct xenbus_device *dev, /* * Enforce precondition before potential leak point. - * blkif_disconnect() is idempotent. + * xen_blkif_disconnect() is idempotent. */ xen_blkif_disconnect(be->blkif); @@ -611,7 +611,7 @@ static void frontend_changed(struct xenbus_device *dev, break; /* fall through if not online */ case XenbusStateUnknown: - /* implies blkif_disconnect() via blkback_remove() */ + /* implies xen_blkif_disconnect() via xen_blkbk_remove() */ device_unregister(&dev->dev); break;