Hi, On Thu, Jan 12, 2023 at 07:09:10PM +0800, Yu Kuai wrote: > Hi, > > 在 2023/01/12 17:43, Artem Chernyshev 写道: > > 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 > > The problem is already fixed in mainline by following patch: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f02be9002c480cd3ec0fcf184ad27cf531bd6ece > > Thanks, > Kuai > > > > 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; > > } > > Sorry, forgot to mention, what behaviour was the same after we applied this patch. Issue was resolved only when we added NULL checking for bfqg. Thanks, Artem
