It is possible for bfqg to be NULL after being initialized as result of
blkg_to_bfqg() function.
That was achieved on kernel 5.15.78, but should exist in mainline as
well
host1 login: [ 460.855794] watchdog: watchdog0: watchdog did not stop!
[ 898.944512] BUG: kernel NULL pointer dereference, address: 0000000000000094
[ 899.285776] #PF: supervisor read access in kernel mode
[ 899.536511] #PF: error_code(0x0000) - not-present page
[ 899.647305] connection4:0: detected conn error (1020)
[ 899.786794] PGD 0 P4D 0
[ 899.786799] Oops: 0000 [#1] SMP PTI
[ 899.786802] CPU: 15 PID: 6073 Comm: ID iothread1 Not tainted 5.15.78-1.el7virt.x86_64 #1
[ 899.786804] Hardware name: HP ProLiant DL360 Gen9/ProLiant DL360 Gen9, BIOS P89 10/21/2019
[ 899.786806] RIP: 0010:bfq_bio_bfqg+0x26/0x80
[ 901.325944] Code: 0f 1f 40 00 0f 1f 44 00 00 55 48 89 fd 48 89 f7 53 48 8b 56 48 48 85 d2
74 32 48 63 05 83 7f 35 01 48 83 c0 16 48 8b 5c c2 08 <80> bb 94 00 00 00 00 00
[ 902.237825] RSP: 0018:ffffae2649437688 EFLAGS: 00010002
[ 902.493396] RAX: 0000000000000019 RBX: 0000000000000000 RCX: dead000000000122
[ 902.841529] RDX: ffff8b6012cb3a00 RSI: ffff8b71002bbed0 RDI: ffff8b71002bbed0
[ 903.189374] RBP: ffff8b601c46e800 R08: ffffae26494377c8 R09: 0000000000000000
[ 903.532985] R10: 0000000000000001 R11: 0000000000000008 R12: ffff8b6f844c5b30
[ 903.880809] R13: ffff8b601c46e800 R14: ffffae2649437760 R15: ffff8b601c46e800
[ 904.220054] FS: 00007fec2fc4a700(0000) GS:ffff8b7f7f640000(0000) kn1GS:00000000000000000
[ 904.614349] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 904.894717] CR2: 0000000000000094 CR3: 0000000111fd8002 CR4: 00000000003726e0
[ 905.243702] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 905.592493] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 905.936859] Call Trace:
[ 906.055955] <TASK>
[ 906.158109] bfq_bic_update_cgroup+0x2c/0x1f0
[ 906.371057] bfq_insert_requests+0x2c2/0x1fb0
[ 906.579207] blk_mq_sched_insert_request+0xc2/0x140
[ 906.817640] __blk_mq_try_issue_directly+0xe0/0x1f0
[ 907.055737] blk_mq_request_issue_directly+0x4e/0xa0
[ 907.298547] dm_mq_queue_rq+0x217/0x3e0
[ 907.485935] blk_mq_dispatch_rq_list+0x14b/0x860
[ 907.711973] ? sbitmap_get+0x87/0x1a0
[ 907.890370] blk_mq_do_dispatch_sched+0x350/0x3b0
[ 908.074869] NMI watchdog: Watchdog detected hard LOCKUP on cpu 40
Fixes: 075a53b78b81 ("bfq: Make sure bfqg for which we are queueing requests is online")
Co-developed-by: Anton Fadeev <anton.fadeev@xxxxxxxxxxx>
Signed-off-by: Anton Fadeev <anton.fadeev@xxxxxxxxxxx>
Signed-off-by: Artem Chernyshev <artem.chernyshev@xxxxxxxxxxx>
---
block/bfq-cgroup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 1b2829e99dad..d4e9428cdbe5 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -616,7 +616,7 @@ struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)
continue;
}
bfqg = blkg_to_bfqg(blkg);
- if (bfqg->online) {
+ if (bfqg && bfqg->online) {
bio_associate_blkg_from_css(bio, &blkg->blkcg->css);
return bfqg;
}
--
2.30.3
