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SubjectRe: [PATCH] bcache: fix panic due to cache_set is null
Date
On 11/30/20 7:21 PM, Yi Li wrote:
> bcache_device_detach will release the cache_set after hotunplug cache
> disk. update_writeback_rate should check validate of cache_set.
>

I see the kernel is 4.4.0+10, do you try the the v5.9 kernel ? I don't
see your kernel code, it is not easy to response.

Thanks.

Coly LI

> IP: [<ffffffffa03730c9>] update_writeback_rate+0x59/0x3a0 [bcache]
> PGD 879620067 PUD 8755d3067 PMD 0
> Oops: 0000 [#1] SMP
> CPU: 8 PID: 1005702 Comm: kworker/8:0 Tainted: G 4.4.0+10 #1
> Hardware name: Intel BIOS SE5C610.86B.01.01.0021.032120170601 03/21/2017
> Workqueue: events update_writeback_rate [bcache]
> task: ffff8808786f3800 ti: ffff88077082c000 task.ti: ffff88077082c000
> RIP: e030:[<ffffffffa03730c9>] update_writeback_rate+0x59/0x3a0 [bcache]
> RSP: e02b:ffff88077082fde0 EFLAGS: 00010202
> RAX: 0000000000000018 RBX: ffff8808047f0b08 RCX: 0000000000000000
> RDX: 0000000000000001 RSI: ffff88088170dab8 RDI: ffff88088170dab8
> RBP: ffff88077082fe18 R08: 000000000000000a R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000017bc8 R12: 0000000000000000
> R13: ffff8808047f0000 R14: 0000000000000200 R15: ffff8808047f0b08
> FS: 00007f157b6d6700(0000) GS:ffff880881700000(0000) knlGS:0000000000000000
> CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000368 CR3: 0000000875c05000 CR4: 0000000000040660
> Stack:
> 0000000000000001 0000000000007ff0 ffff88085ff600c0 ffff880881714e80
> ffff880881719500 0000000000000200 ffff8808047f0b08 ffff88077082fe60
> ffffffff81088c0c 0000000081714e80 0000000000000000 ffff880881714e80
> Call Trace:
> [<ffffffff81088c0c>] process_one_work+0x1fc/0x3b0
> [<ffffffff81089575>] worker_thread+0x2a5/0x470
> [<ffffffff815a2f58>] ? __schedule+0x648/0x870
> [<ffffffff810892d0>] ? rescuer_thread+0x300/0x300
> [<ffffffff8108e3d5>] kthread+0xd5/0xe0
> [<ffffffff8108e300>] ? kthread_stop+0x110/0x110
> [<ffffffff815a704f>] ret_from_fork+0x3f/0x70
> [<ffffffff8108e300>] ? kthread_stop+0x110/0x110
>
> Reported-by: Guo Chao <guochao@winhong.com>
> Signed-off-by: Guo Chao <guochao@winhong.com>
> Signed-off-by: Yi Li <yili@winhong.com>
> ---
> drivers/md/bcache/writeback.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
> index 3c74996978da..186c4c6e1607 100644
> --- a/drivers/md/bcache/writeback.c
> +++ b/drivers/md/bcache/writeback.c
> @@ -175,7 +175,15 @@ static void update_writeback_rate(struct work_struct *work)
> struct cached_dev *dc = container_of(to_delayed_work(work),
> struct cached_dev,
> writeback_rate_update);
> - struct cache_set *c = dc->disk.c;
> + struct cache_set *c = NULL;
> +
> + mutex_lock(&bch_register_lock);
> + c = dc->disk.c;
> +
> + if (c == NULL) {
> + mutex_unlock(&bch_register_lock);
> + return;
> + }
>
> /*
> * should check BCACHE_DEV_RATE_DW_RUNNING before calling
> @@ -194,6 +202,7 @@ static void update_writeback_rate(struct work_struct *work)
> clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
> /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
> smp_mb__after_atomic();
> + mutex_unlock(&bch_register_lock);
> return;
> }
>
> @@ -230,6 +239,7 @@ static void update_writeback_rate(struct work_struct *work)
> clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
> /* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
> smp_mb__after_atomic();
> + mutex_unlock(&bch_register_lock);
> }
>
> static unsigned int writeback_delay(struct cached_dev *dc,
>

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