Current kernel (d2980d8d) crashes
when blk_iocost_init for `nvme1` disk.

	BUG: kernel NULL pointer dereference, address: 0000000000000050
	#PF: supervisor read access in kernel mode
	#PF: error_code(0x0000) - not-present page

	blk_iocost_init (include/asm-generic/qspinlock.h:128
			 include/linux/spinlock.h:203
			 include/linux/spinlock_api_smp.h:158
			 include/linux/spinlock.h:400
			 block/blk-iocost.c:2884)
	ioc_qos_write (block/blk-iocost.c:3198)
	? kretprobe_perf_func (kernel/trace/trace_kprobe.c:1566)
	? kernfs_fop_write_iter (include/linux/slab.h:584 fs/kernfs/file.c:311)
	? __kmem_cache_alloc_node (mm/slab.h:? mm/slub.c:3452 mm/slub.c:3491)
	? _copy_from_iter (arch/x86/include/asm/uaccess_64.h:46
			   arch/x86/include/asm/uaccess_64.h:52
			   lib/iov_iter.c:183 lib/iov_iter.c:628)
	? kretprobe_dispatcher (kernel/trace/trace_kprobe.c:1693)
	cgroup_file_write (kernel/cgroup/cgroup.c:4061)
	kernfs_fop_write_iter (fs/kernfs/file.c:334)
	vfs_write (include/linux/fs.h:1849 fs/read_write.c:491
		   fs/read_write.c:584)
	ksys_write (fs/read_write.c:637)
	do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80)
	entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)

This happens because ioc_refresh_params() is being called without
a properly initialized ioc->rqos, which is happening later in the callee
side.

ioc_refresh_params() -> ioc_autop_idx() tries to access
ioc->rqos.disk->queue but ioc->rqos.disk is NULL, causing the BUG above.

Create function, called ioc_refresh_params_disk(), that is similar to
ioc_refresh_params() but where the "struct gendisk" could be passed as
an explicit argument. This function will be called when ioc->rqos.disk
is not initialized.

Fixes: ce57b558 ("blk-rq-qos: make rq_qos_add and rq_qos_del more useful")
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230228111654.1778120-1-leitao@debian.orgReviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>