[PATCH] scsi: Fix a bdi reregistration race

[PATCH] scsi: Fix a bdi reregistration race

[Bart Van Assche]

Unregister and reregister BDI devices in the proper order. This patch
avoids that the following kernel warning can get triggered:

WARNING: CPU: 7 PID: 203 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x68/0x80()
sysfs: cannot create duplicate filename '/devices/virtual/bdi/8:32'
Workqueue: events_unbound async_run_entry_fn
Call Trace:
[<ffffffff814ff5a4>] dump_stack+0x4c/0x65
[<ffffffff810746ba>] warn_slowpath_common+0x8a/0xc0
[<ffffffff81074736>] warn_slowpath_fmt+0x46/0x50
[<ffffffff81237ca8>] sysfs_warn_dup+0x68/0x80
[<ffffffff81237d8e>] sysfs_create_dir_ns+0x7e/0x90
[<ffffffff81291f58>] kobject_add_internal+0xa8/0x320
[<ffffffff812923a0>] kobject_add+0x60/0xb0
[<ffffffff8138c937>] device_add+0x107/0x5e0
[<ffffffff8138d018>] device_create_groups_vargs+0xd8/0x100
[<ffffffff8138d05c>] device_create_vargs+0x1c/0x20
[<ffffffff8117f233>] bdi_register+0x63/0x2a0
[<ffffffff8117f497>] bdi_register_dev+0x27/0x30
[<ffffffff81281549>] add_disk+0x1a9/0x4e0
[<ffffffffa00c5739>] sd_probe_async+0x119/0x1d0 [sd_mod]
[<ffffffff8109a81a>] async_run_entry_fn+0x4a/0x140
[<ffffffff81091078>] process_one_work+0x1d8/0x7c0
[<ffffffff81091774>] worker_thread+0x114/0x460
[<ffffffff81097878>] kthread+0xf8/0x110
[<ffffffff8150801f>] ret_from_fork+0x3f/0x70

See also patch "block: destroy bdi before blockdev is unregistered"
(commit ID 6cd18e711dd8).

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: <stable@vger.kernel.org>
---
 drivers/scsi/scsi_sysfs.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index b333389..5e085d4 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1084,9 +1084,7 @@ void __scsi_remove_device(struct scsi_device *sdev)
 		device_unregister(&sdev->sdev_dev);
 		transport_remove_device(dev);
 		scsi_dh_remove_device(sdev);
-		device_del(dev);
-	} else
-		put_device(&sdev->sdev_dev);
+	}
 
 	/*
 	 * Stop accepting new requests and wait until all queuecommand() and
@@ -1097,6 +1095,16 @@ void __scsi_remove_device(struct scsi_device *sdev)
 	blk_cleanup_queue(sdev->request_queue);
 	cancel_work_sync(&sdev->requeue_work);
 
+	/*
+	 * Remove the device after blk_cleanup_queue() has been called such
+	 * a possible bdi_register() call with the same name occurs after
+	 * blk_cleanup_queue() has called bdi_destroy().
+	 */
+	if (sdev->is_visible)
+		device_del(dev);
+	else
+		put_device(&sdev->sdev_dev);
+
 	if (sdev->host->hostt->slave_destroy)
 		sdev->host->hostt->slave_destroy(sdev);
 	transport_destroy_device(dev);
-- 
2.1.4

Re: [PATCH] scsi: Fix a bdi reregistration race

[Hannes Reinecke]

On 09/19/2015 02:23 AM, Bart Van Assche wrote:
> Unregister and reregister BDI devices in the proper order. This patch
> avoids that the following kernel warning can get triggered:
> 
> WARNING: CPU: 7 PID: 203 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x68/0x80()
> sysfs: cannot create duplicate filename '/devices/virtual/bdi/8:32'
> Workqueue: events_unbound async_run_entry_fn
> Call Trace:
> [<ffffffff814ff5a4>] dump_stack+0x4c/0x65
> [<ffffffff810746ba>] warn_slowpath_common+0x8a/0xc0
> [<ffffffff81074736>] warn_slowpath_fmt+0x46/0x50
> [<ffffffff81237ca8>] sysfs_warn_dup+0x68/0x80
> [<ffffffff81237d8e>] sysfs_create_dir_ns+0x7e/0x90
> [<ffffffff81291f58>] kobject_add_internal+0xa8/0x320
> [<ffffffff812923a0>] kobject_add+0x60/0xb0
> [<ffffffff8138c937>] device_add+0x107/0x5e0
> [<ffffffff8138d018>] device_create_groups_vargs+0xd8/0x100
> [<ffffffff8138d05c>] device_create_vargs+0x1c/0x20
> [<ffffffff8117f233>] bdi_register+0x63/0x2a0
> [<ffffffff8117f497>] bdi_register_dev+0x27/0x30
> [<ffffffff81281549>] add_disk+0x1a9/0x4e0
> [<ffffffffa00c5739>] sd_probe_async+0x119/0x1d0 [sd_mod]
> [<ffffffff8109a81a>] async_run_entry_fn+0x4a/0x140
> [<ffffffff81091078>] process_one_work+0x1d8/0x7c0
> [<ffffffff81091774>] worker_thread+0x114/0x460
> [<ffffffff81097878>] kthread+0xf8/0x110
> [<ffffffff8150801f>] ret_from_fork+0x3f/0x70
> 
> See also patch "block: destroy bdi before blockdev is unregistered"
> (commit ID 6cd18e711dd8).
> 
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: <stable@vger.kernel.org>
> ---
>  drivers/scsi/scsi_sysfs.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index b333389..5e085d4 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1084,9 +1084,7 @@ void __scsi_remove_device(struct scsi_device *sdev)
>  		device_unregister(&sdev->sdev_dev);
>  		transport_remove_device(dev);
>  		scsi_dh_remove_device(sdev);
> -		device_del(dev);
> -	} else
> -		put_device(&sdev->sdev_dev);
> +	}
>  
>  	/*
>  	 * Stop accepting new requests and wait until all queuecommand() and
> @@ -1097,6 +1095,16 @@ void __scsi_remove_device(struct scsi_device *sdev)
>  	blk_cleanup_queue(sdev->request_queue);
>  	cancel_work_sync(&sdev->requeue_work);
>  
> +	/*
> +	 * Remove the device after blk_cleanup_queue() has been called such
> +	 * a possible bdi_register() call with the same name occurs after
> +	 * blk_cleanup_queue() has called bdi_destroy().
> +	 */
> +	if (sdev->is_visible)
> +		device_del(dev);
> +	else
> +		put_device(&sdev->sdev_dev);
> +
>  	if (sdev->host->hostt->slave_destroy)
>  		sdev->host->hostt->slave_destroy(sdev);
>  	transport_destroy_device(dev);
> 
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
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Re: [PATCH] scsi: Fix a bdi reregistration race

[Sagi Grimberg]

On 9/19/2015 3:23 AM, Bart Van Assche wrote:
> Unregister and reregister BDI devices in the proper order. This patch
> avoids that the following kernel warning can get triggered:

Hi Bart,

Can you share the scenario that reproduced this? I think I might
have seen this before.

Thanks,
Sagi.

Re: [PATCH] scsi: Fix a bdi reregistration race

[Bart Van Assche]

On 09/20/15 02:57, Sagi Grimberg wrote:
> On 9/19/2015 3:23 AM, Bart Van Assche wrote:
>> Unregister and reregister BDI devices in the proper order. This patch
>> avoids that the following kernel warning can get triggered:
>
> Can you share the scenario that reproduced this? I think I might
> have seen this before.

Hello Sagi,

The details of the setup on which I can reproduce the reported behavior 
easily are as follows:
* Several kernel debugging options were enabled on the initiator system
   (PROVE_LOCKING, SLUB_DEBUG, KMEMLEAK, ...).
* srp_daemon and multipathd were running on the initiator system.
* Four IB ports were present the initiator system.
* Eight IB ports were present the target system.
* 100 LUNs were defined on the target system.
* As a result, 3200 /dev/sd* device nodes were created on the
   initiator system by the SRP initiator driver.
* The following command was run on the initiator system:
   for p in /sys/class/srp_remote_ports/*; do echo 1 >$p/delete & done;
   wait; dmsetup remove_all

Bart.