Messages in this thread Patch in this message | | | Date | Fri, 14 Mar 2014 02:34:58 -0700 | From | Christoph Hellwig <> | Subject | Re: [PATCH 1/1] block: rework flush sequencing for blk-mq |
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On Fri, Mar 14, 2014 at 02:25:19AM -0700, Christoph Hellwig wrote: > b) is a bit harder, but we should think hard about it when rewriting the > multipath code to support blk-mq. Talking about which I think trying to > use dm-multipath on any blk-mq device will go horribly crash and boom at > the moment.
Talking abnout crashing and burning.. Hannes, did you run this patch past dm-devel and linux-scsi yet? Don't quite like it but the problem seems real..
From: Hannes Reinecke <hare@suse.de> Subject: Kernel bug triggered in multipath References: bnc#486001 Patch-mainline: not yet
Starting multipath on a cciss device will cause a kernel warning to be triggered. Problem is that we're using the ->queuedata field of the request_queue to derefence the scsi device; however, for other (non-SCSI) devices this points to a totally different structure. So we should rather be using accessors here which make sure we're only returning valid SCSI device structures.
Signed-off-by: Hannes Reinecke <hare@suse.de>
--- drivers/scsi/device_handler/scsi_dh.c | 10 +++++----- drivers/scsi/scsi_lib.c | 11 +++++++++++ include/scsi/scsi_device.h | 1 + 3 files changed, 17 insertions(+), 5 deletions(-)
--- a/drivers/scsi/device_handler/scsi_dh.c +++ b/drivers/scsi/device_handler/scsi_dh.c @@ -397,7 +397,7 @@ int scsi_dh_activate(struct request_queu struct device *dev = NULL; spin_lock_irqsave(q->queue_lock, flags); - sdev = q->queuedata; + sdev = scsi_device_from_queue(q); if (!sdev) { spin_unlock_irqrestore(q->queue_lock, flags); err = SCSI_DH_NOSYS; @@ -484,7 +484,7 @@ int scsi_dh_attach(struct request_queue return -EINVAL; spin_lock_irqsave(q->queue_lock, flags); - sdev = q->queuedata; + sdev = scsi_device_from_queue(q); if (!sdev || !get_device(&sdev->sdev_gendev)) err = -ENODEV; spin_unlock_irqrestore(q->queue_lock, flags); @@ -512,7 +512,7 @@ void scsi_dh_detach(struct request_queue struct scsi_device_handler *scsi_dh = NULL; spin_lock_irqsave(q->queue_lock, flags); - sdev = q->queuedata; + sdev = scsi_device_from_queue(q); if (!sdev || !get_device(&sdev->sdev_gendev)) sdev = NULL; spin_unlock_irqrestore(q->queue_lock, flags); --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1594,6 +1594,17 @@ out: spin_lock_irq(q->queue_lock); } +struct scsi_device *scsi_device_from_queue(struct request_queue *q) +{ + struct scsi_device *sdev = NULL; + + if (q->request_fn == scsi_request_fn) + sdev = q->queuedata; + + return sdev; +} +EXPORT_SYMBOL_GPL(scsi_device_from_queue); + u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost) { struct device *host_dev; --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -300,6 +300,7 @@ extern void starget_for_each_device(stru extern void __starget_for_each_device(struct scsi_target *, void *, void (*fn)(struct scsi_device *, void *)); +extern struct scsi_device *scsi_device_from_queue(struct request_queue *); /* only exposed to implement shost_for_each_device */ extern struct scsi_device *__scsi_iterate_devices(struct Scsi_Host *,
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