FUJITA Tomonori wrote: > On Sun, 30 Mar 2008 12:39:36 -0500 > James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > >> On Thu, 2008-03-27 at 21:18 +0900, FUJITA Tomonori wrote: >>> On Thu, 27 Mar 2008 20:11:52 +0900 >>> FUJITA Tomonori <tomof@xxxxxxx> wrote: >>> >>>> On Wed, 26 Mar 2008 20:51:44 -0500 >>>> Mike Christie <michaelc@xxxxxxxxxxx> wrote: >>>> >>>>> FUJITA Tomonori wrote: >>>>>> On Wed, 26 Mar 2008 07:36:26 -0700 >>>>>> James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: >>>>>> >>>>>>> On Wed, 2008-03-26 at 23:22 +0900, FUJITA Tomonori wrote: >>>>>>>> On Sat, 22 Mar 2008 11:06:00 -0500 >>>>>>>> James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: >>>>>>>> >>>>>>>>> On Tue, 2008-03-11 at 00:36 -0500, Mike Christie wrote: >>>>>>>>>> Mike Christie wrote: >>>>>>>>>>> Pete Wyckoff wrote: >>>>>>>>>>>> I think this used not to happen; not sure. But I changed two things >>>>>>>>>>> This most likely did not happen before 2.6.25-rc* or it broke in >>>>>>>>>>> slightly different ways, because iscsi used to try and do >>>>>>>>>>> >>>>>>>>>>> echo 1 > /sys/block/sdX/device/delete >>>>>>>>>>> >>>>>>>>>>> from userspace instead of calling scsi_remove_target from the kernel. >>>>>>>>>>> >>>>>>>>>>> As you know around 2.6.21, the behavior of doing the echo to the delete >>>>>>>>>>> file changed due to a driver model and scsi change and that broke the >>>>>>>>>>> iscsi tools. The iscsi tools userspace removal was sort of hack in the >>>>>>>>>>> first place and was racey, so we switched to removing devices/target >>>>>>>>>>> like the FC class. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>>> lately. 2.6.25-rc1 to -rc4 and fedora 8 iscsi-initiator-utils (865) to >>>>>>>>>>>> fedora devel (868). Bidi and varlen patches always too. >>>>>>>>>>>> >>>>>>>>>>>> I'll follow with some more variations on this theme. Looks like bsg >>>>>>>>>>>> needs to protect more carefully against the device going away. Any >>>>>>>>>>>> ideas how best to do this? What was the approach in sg? >>>>>>>>>>>> >>>>>>>>>>> I think sg is broken in similar ways. The iser guys have some tests >>>>>>>>>>> cases that have broken sg while IO is outstanding. I am ccing Erez. >>>>>>>>>> Actually one of the problems looks a little different than some of the >>>>>>>>>> problems hit with sg and are caused because we remove the bsg device too >>>>>>>>>> soon. I think we want to wait until all the references from the >>>>>>>>>> commands/requests are released. The attached patch (untested) moves the >>>>>>>>>> bsg unreg call to the scsi device release fn. >>>>>>>>> Well, this fix is now upstream. However, it's causing all our >>>>>>>>> scsi_devices never to get released, which is a serious regression. >>>>>>>>> We're also doing spurious bsg_unregister_queue() for things that never >>>>>>>>> actually registered one (all scan devices that return DID_NO_CONNECT), >>>>>>>>> but bsg doesn't seem to be complaining about this. >>>>>>>>> >>>>>>>>> The essence of the problem is that bsg_register_queue() takes a ref to >>>>>>>>> the sdev_gendev, so you can't move bsg_unregister_queue() into the >>>>>>>>> release function because nothing ever puts bsg's device ref and so >>>>>>>>> release is never called. >>>>>>>>> >>>>>>>>> Options for fixing this before 2.6.25 are >>>>>>>>> >>>>>>>>> 1. revert the patch >>>>>>>>> 2. Do an additional put for the bsg reference in >>>>>>>>> __scsi_remove_device (patch below). It's nasty but it preserves >>>>>>>>> the semantics and does what you want >>>>>>>> After some investigation, this patch doesn't fix the bug that Pete >>>>>>>> reported (I'll send a new patch shortly). >>>>>>>> >>>>>>>> Can you revert the commit 4b6f5b3a993cbe34b4280f252bccc76967c185c8 >>>>>>>> instead of merging this? >>>>>>> Sure ... I didn't like the hack either. As long as iSCSI is fine with >>>>>>> the reversion it's the quickest way to fix the problem. >>>>>> How about this? With the commit reversion, I confirmed that this patch >>>>>> fixes the first bug that Pete reported: >>>>>> >>>>>> http://marc.info/?l=linux-scsi&m=120508166505141&w=2 >>>>>> >>>>>> I suspect that this could fix the rest too. >>>>>> >>>>>> = >>>>>> From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> >>>>>> Subject: [PATCH] bsg: takes a ref to struct device in fops->open >>>>>> >>>>>> bsg_register_queue() takes a ref to struct device that a caller >>>>>> passes. For example, it takes a ref to the sdev_gendev with scsi >>>>>> devices. However, bsg doesn't takes a ref to it in fops->open. So >>>>>> while an application opens a bsg device, the scsi device that the bsg >>>>>> device holds can go away (bsg also takes a ref to a queue, but it >>>>>> doesn't prevent the device from going away). >>>>>> >>>>>> With this, bsg takes a ref to struct device in fops->open and frees it >>>>>> in fops->release. >>>>>> >>>>>> Note that bsg doesn't need to takes a ref to a queue for SCSI devices >>>>>> at least. I think that it would be better to remove the code but I let >>>>>> it alone for now. >>>>>> >>>>> Why does bsg_add_device do kobject_get instead of blk_get_queue? >>>> I think that it's a bug. But both takes a ref to a queue (though >>>> kobject_get doesn't see QUEUE_FLAG_DEAD), so I think that it's not >>>> related with the current problems. >>>> >>>> >>>>> It seems like if we added a blk_qet_queue when we opened the device and >>>>> a blk_put_queue when bsg_release is called we could remove the >>>>> get/put_device calls. I am not sure if that is cleaner or not. I was >>>>> just thinking that bsg goes from bsg->request_queue->scsi_device so >>>>> maybe it should not worry about the device. >>>> kobject_get takes a ref to a queue. If we don't take a ref to a >>>> device, the scsi device has gone though the queue is still there >>>> because the queue release is done from the device release. If the scsi >>>> device has gone, we are dead, right? >>>> >>>> >>>> Anyway, here's a patch to replace kobject_get with blk_get_queue. >>>> >>>> James, please apply this patch too. >>>> >>>> = >>>> From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> >>>> Subject: [PATCH] bsg: replace kobject_get with blk_get_queue >>> Really sorry, please apply this one. >>> >>> = >>> From: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> >>> Subject: [PATCH] bsg: replace kobject_get with blk_get_queue >>> >>> Both takes a ref to a queue. But blk_get_queue checks QUEUE_FLAG_DEAD >>> and is more appropriate interface here. >>> >>> Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx> >>> Cc: Jens Axboe <jens.axboe@xxxxxxxxxx> >>> Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> >> >> This looks reasonable to me. It's probably a rc-fixes patch, so could I >> get Jen's ack and some evidence of testing (and that it actually fixes >> the bug). > > Do you mean that the patch to take a ref to strutc device > (e.g. sdev_gendev for scsi devices) in fops->open is a reasonable fix? > > http://marc.info/?l=linux-scsi&m=120654365424916&w=2 > > The patch with the commit reversion fixes all the problems for me that > Pete reported. Pete, can you test the patch? > > > It's a rc-fixes patch, but I'm fine with applying it to scsi-misc > (I'll send it to the stable tree later on). > > The patch has one bug in an error handling path (I should have used > IS_ERR there). So I'll send an updated version shortly. Hi Tomo. Do you please have an accumulated latest patch for this problem. (Or point me to the right one, I can't find it). I want to test it here too. (Over rc-fixes) Thanks Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
