Hi, Christoph
在 2023/06/01 14:18, Christoph Hellwig 写道:
On Thu, Jun 01, 2023 at 09:50:22AM +0800, Yu Kuai wrote:
Hi, Christoph
在 2023/05/31 20:44, Christoph Hellwig 写道:
I like where this is going, but did you check that this doesn't
introduce a potential crash with the current /dev/sg based blktrace?
I just start to look at how /dev/sg is created and destroyed, however,
I'm confused here, do you mean that the added blk_trace_shutdown() here
might cause that /dev/sg blktrace to access freed momory or NULL
pointer?
Yes. Given that __blk_trace_remove clears out q->blk_trace and
frees the blk trace structure I'm worried about that.
sg ioctl call blktrace apis blk_trace_setup/startstop/remove(), and
these apis are all protected by 'q->debugfs_mutex', and they're safe
to call at anytime as long as request_queue is not released.
And I found that it's true sg can still enable blktrace through ioctl
after the related scsi device gendisk is released, I'm thinking about
following possible solution:
sg_device_destroy() is called at last, when all openers close and the
related device is deleted, so, I think we can get a queue reference
while initializing /dev/sg, and then remove blktrace and put queue
reference from sg_device_destroy().
Any suggestions?
Thanks,
Kuai
