Messages in this thread Patch in this message | | | Subject | Re: [PATCH] scsi/sg: don't grab scsi host module reference | From | Yu Kuai <> | Date | Wed, 5 Jul 2023 10:28:45 +0800 |
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Hi,
在 2023/07/05 9:43, Yu Kuai 写道: > Hi, > > 在 2023/07/05 1:04, Marc Hartmayer 写道: >> On Thu, Jun 22, 2023 at 12:01 AM +0800, Yu Kuai >> <yukuai1@huaweicloud.com> wrote: >>> From: Yu Kuai <yukuai3@huawei.com> >>> >>> In order to prevent request_queue to be freed before cleaning up >>> blktrace debugfs entries, commit db59133e9279 ("scsi: sg: fix blktrace >>> debugfs entries leakage") use scsi_device_get(), however, >>> scsi_device_get() will also grab scsi module reference and scsi module >>> can't be removed. >>> >>> It's reported that blktests can't unload scsi_debug after block/001: >>> >>> blktests (master) # ./check block >>> block/001 (stress device hotplugging) [failed] >>> +++ /root/blktests/results/nodev/block/001.out.bad 2023-06-19 >>> Running block/001 >>> Stressing sd >>> +modprobe: FATAL: Module scsi_debug is in use. >>> >>> Fix this problem by grabbing request_queue reference directly, so that >>> scsi host module can still be unloaded while request_queue will be >>> pinged by sg device. >>> >>> Reported-by: Chaitanya Kulkarni <chaitanyak@nvidia.com> >>> Link: >>> https://lore.kernel.org/all/1760da91-876d-fc9c-ab51-999a6f66ad50@nvidia.com/ >>> >>> Fixes: db59133e9279 ("scsi: sg: fix blktrace debugfs entries leakage") >>> Signed-off-by: Yu Kuai <yukuai3@huawei.com> >>> --- >>> drivers/scsi/sg.c | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c >>> index 2433eeef042a..dcb73787c29d 100644 >>> --- a/drivers/scsi/sg.c >>> +++ b/drivers/scsi/sg.c >>> @@ -1497,7 +1497,7 @@ sg_add_device(struct device *cl_dev) >>> int error; >>> unsigned long iflags; >>> - error = scsi_device_get(scsidp); >>> + error = blk_get_queue(scsidp->request_queue); >>> if (error) >>> return error; >>> @@ -1558,7 +1558,7 @@ sg_add_device(struct device *cl_dev) >>> out: >>> if (cdev) >>> cdev_del(cdev); >>> - scsi_device_put(scsidp); >>> + blk_put_queue(scsidp->request_queue); >>> return error; >>> } >>> @@ -1575,7 +1575,7 @@ sg_device_destroy(struct kref *kref) >>> */ >>> blk_trace_remove(q); >>> - scsi_device_put(sdp->device); >>> + blk_put_queue(q); >>> write_lock_irqsave(&sg_index_lock, flags); >>> idr_remove(&sg_index_idr, sdp->index); >>> -- >>> 2.39.2 >> >> Hi, >> >> This change (bisected) triggers a regression in our KVM on s390x CI. The >> symptom is that a “scsi_debug device” does not bind to the scsi_generic >> driver. On s390x you can reproduce the problem as follows (I have not >> tested on x86): >> >> With this patch applied: >> >> $ sudo modprobe scsi_debug >> $ # Get the 'scsi_host,channel,target_number,LUN' tuple for the >> scsi_debug device >> $ lsscsi |grep scsi_debug |awk '{ print $1 }' >> [0:0:0:0] >> $ sudo stat /sys/bus/scsi/devices/0:0:0:0/scsi_generic >> stat: cannot statx '/sys/bus/scsi/devices/0:0:0:0/scsi_generic': No >> such file or directory >> >> >> Patch reverted: >> > > I didn't figure out the root cause, howver, have you tried to reviert > this patch as well? > > db59133e9279 ("scsi: sg: fix blktrace debugfs entries leakage"
Never mind this, root cause is that the checking of return value of blk_get_queue() is wrong.
This shoud be fixed by following patch:
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 89fa046c7158..0d8afffd1683 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1497,9 +1497,10 @@ sg_add_device(struct device *cl_dev) int error; unsigned long iflags;
- error = blk_get_queue(scsidp->request_queue); - if (error) - return error; + if (!blk_get_queue(scsidp->request_queue)) { + pr_warn("%s: get scsi_device queue failed\n", __func__); + return -ENODEV; + }
error = -ENOMEM; cdev = cdev_alloc(); > > Thanks, > Kuai >> $ sudo modprobe scsi_debug >> $ lsscsi |grep scsi_debug |awk '{ print $1 }' >> [0:0:0:0] >> $ sudo stat /sys/bus/scsi/devices/0:0:0:0/scsi_generic >> File: /sys/bus/scsi/devices/0:0:0:0/scsi_generic >> Size: 0 Blocks: 0 IO Block: 4096 directory >> Device: 0,20 Inode: 12155 Links: 3 >> … >> >> Any ideas? >> >> Marc >> . >> > > . >
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