md: fix NULL pointer deref with nowait but no mddev->queue

Leon reported NULL pointer deref with nowait support:

[   15.123761] device-mapper: raid: Loading target version 1.15.1
[   15.124185] device-mapper: raid: Ignoring chunk size parameter for RAID 1
[   15.124192] device-mapper: raid: Choosing default region size of 4MiB
[   15.129524] BUG: kernel NULL pointer dereference, address: 0000000000000060
[   15.129530] #PF: supervisor write access in kernel mode
[   15.129533] #PF: error_code(0x0002) - not-present page
[   15.129535] PGD 0 P4D 0
[   15.129538] Oops: 0002 [#1] PREEMPT SMP NOPTI
[   15.129541] CPU: 5 PID: 494 Comm: ldmtool Not tainted 5.17.0-rc2-1-mainline #1 9fe89d43dfcb215d2731e6f8851740520778615e
[   15.129546] Hardware name: Gigabyte Technology Co., Ltd. X570 AORUS ELITE/X570 AORUS ELITE, BIOS F36e 10/14/2021
[   15.129549] RIP: 0010:blk_queue_flag_set+0x7/0x20
[   15.129555] Code: 00 00 00 0f 1f 44 00 00 48 8b 35 e4 e0 04 02 48 8d 57 28 bf 40 01 \
       00 00 e9 16 c1 be ff 66 0f 1f 44 00 00 0f 1f 44 00 00 89 ff <f0> 48 0f ab 7e 60 \
       31 f6 89 f7 c3 66 66 2e 0f 1f 84 00 00 00 00 00
[   15.129559] RSP: 0018:ffff966b81987a88 EFLAGS: 00010202
[   15.129562] RAX: ffff8b11c363a0d0 RBX: ffff8b11e294b070 RCX: 0000000000000000
[   15.129564] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000001d
[   15.129566] RBP: ffff8b11e294b058 R08: 0000000000000000 R09: 0000000000000000
[   15.129568] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8b11e294b070
[   15.129570] R13: 0000000000000000 R14: ffff8b11e294b000 R15: 0000000000000001
[   15.129572] FS:  00007fa96e826780(0000) GS:ffff8b18deb40000(0000) knlGS:0000000000000000
[   15.129575] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   15.129577] CR2: 0000000000000060 CR3: 000000010b8ce000 CR4: 00000000003506e0
[   15.129580] Call Trace:
[   15.129582]  <TASK>
[   15.129584]  md_run+0x67c/0xc70 [md_mod 1e470c1b6bcf1114198109f42682f5a2740e9531]
[   15.129597]  raid_ctr+0x134a/0x28ea [dm_raid 6a645dd7519e72834bd7e98c23497eeade14cd63]
[   15.129604]  ? dm_split_args+0x63/0x150 [dm_mod 0d7b0bc3414340a79c4553bae5ca97294b78336e]
[   15.129615]  dm_table_add_target+0x188/0x380 [dm_mod 0d7b0bc3414340a79c4553bae5ca97294b78336e]
[   15.129625]  table_load+0x13b/0x370 [dm_mod 0d7b0bc3414340a79c4553bae5ca97294b78336e]
[   15.129635]  ? dev_suspend+0x2d0/0x2d0 [dm_mod 0d7b0bc3414340a79c4553bae5ca97294b78336e]
[   15.129644]  ctl_ioctl+0x1bd/0x460 [dm_mod 0d7b0bc3414340a79c4553bae5ca97294b78336e]
[   15.129655]  dm_ctl_ioctl+0xa/0x20 [dm_mod 0d7b0bc3414340a79c4553bae5ca97294b78336e]
[   15.129663]  __x64_sys_ioctl+0x8e/0xd0
[   15.129667]  do_syscall_64+0x5c/0x90
[   15.129672]  ? syscall_exit_to_user_mode+0x23/0x50
[   15.129675]  ? do_syscall_64+0x69/0x90
[   15.129677]  ? do_syscall_64+0x69/0x90
[   15.129679]  ? syscall_exit_to_user_mode+0x23/0x50
[   15.129682]  ? do_syscall_64+0x69/0x90
[   15.129684]  ? do_syscall_64+0x69/0x90
[   15.129686]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[   15.129689] RIP: 0033:0x7fa96ecd559b
[   15.129692] Code: ff ff ff 85 c0 79 9b 49 c7 c4 ff ff ff ff 5b 5d 4c 89 e0 41 5c \
    c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff \
    ff 73 01 c3 48 8b 0d a5 a8 0c 00 f7 d8 64 89 01 48
[   15.129696] RSP: 002b:00007ffcaf85c258 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
[   15.129699] RAX: ffffffffffffffda RBX: 00007fa96f1b48f0 RCX: 00007fa96ecd559b
[   15.129701] RDX: 00007fa97017e610 RSI: 00000000c138fd09 RDI: 0000000000000003
[   15.129702] RBP: 00007fa96ebab583 R08: 00007fa97017c9e0 R09: 00007ffcaf85bf27
[   15.129704] R10: 0000000000000001 R11: 0000000000000206 R12: 00007fa97017e610
[   15.129706] R13: 00007fa97017e640 R14: 00007fa97017e6c0 R15: 00007fa97017e530
[   15.129709]  </TASK>

This is caused by missing mddev->queue check for setting QUEUE_FLAG_NOWAIT
Fix this by moving the QUEUE_FLAG_NOWAIT logic to under mddev->queue check.

Fixes: f51d46d0 ("md: add support for REQ_NOWAIT")
Reported-by: Leon Möller <jkhsjdhjs@totally.rip>
Tested-by: Leon Möller <jkhsjdhjs@totally.rip>
Cc: Vishal Verma <vverma@digitalocean.com>
Signed-off-by: Song Liu <song@kernel.org>

drivers/md/md.c

@@ -5869,10 +5869,6 @@ int md_run(struct mddev *mddev)
 		nowait = nowait && blk_queue_nowait(bdev_get_queue(rdev->bdev));
 	}
 
-	/* Set the NOWAIT flags if all underlying devices support it */
-	if (nowait)
-		blk_queue_flag_set(QUEUE_FLAG_NOWAIT, mddev->queue);
-
 	if (!bioset_initialized(&mddev->bio_set)) {
 		err = bioset_init(&mddev->bio_set, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS);
 		if (err)
@@ -6010,6 +6006,10 @@ int md_run(struct mddev *mddev)
 		else
 			blk_queue_flag_clear(QUEUE_FLAG_NONROT, mddev->queue);
 		blk_queue_flag_set(QUEUE_FLAG_IO_STAT, mddev->queue);
+
+		/* Set the NOWAIT flags if all underlying devices support it */
+		if (nowait)
+			blk_queue_flag_set(QUEUE_FLAG_NOWAIT, mddev->queue);
 	}
 	if (pers->sync_request) {
 		if (mddev->kobj.sd &&