[PATCH 1/1] bcache: release the lock before stopping the writeback thread

[PATCH 1/1] bcache: release the lock before stopping the writeback thread

[Shan Hai]

The writeback thread would exit with a lock held when the cache device is
detached via sysfs interface, fix it by releasing the held lock before exiting
the thread.

Signed-off-by: Shan Hai <shan.hai@oracle.com>
---
 drivers/md/bcache/writeback.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 481d4cf..adc583f 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -679,8 +679,10 @@ static int bch_writeback_thread(void *arg)
 			 * data on cache. BCACHE_DEV_DETACHING flag is set in
 			 * bch_cached_dev_detach().
 			 */
-			if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
+			if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
+				up_write(&dc->writeback_lock);
 				break;
+			}
 		}
 
 		up_write(&dc->writeback_lock);
-- 
2.7.4

Re: [PATCH 1/1] bcache: release the lock before stopping the writeback thread

[Coly Li]

Hi Shan,

On 2018/8/22 3:00 PM, Shan Hai wrote:
> The writeback thread would exit with a lock held when the cache device is
> detached via sysfs interface, fix it by releasing the held lock before exiting
> the thread.

I will change "the thread" to "the while-loop" when I apply this patch.

> 
> Signed-off-by: Shan Hai <shan.hai@oracle.com>

Nice catch!

This one should go to stable trees since 4.17 as well. I will CC stable
maintainers when I submit this one for 4.19.

Thank you for the fix.

Coly Li

> ---
>  drivers/md/bcache/writeback.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
> index 481d4cf..adc583f 100644
> --- a/drivers/md/bcache/writeback.c
> +++ b/drivers/md/bcache/writeback.c
> @@ -679,8 +679,10 @@ static int bch_writeback_thread(void *arg)
>  			 * data on cache. BCACHE_DEV_DETACHING flag is set in
>  			 * bch_cached_dev_detach().
>  			 */
> -			if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
> +			if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
> +				up_write(&dc->writeback_lock);
>  				break;
> +			}
>  		}
>  
>  		up_write(&dc->writeback_lock);
> 

Re: [PATCH 1/1] bcache: release the lock before stopping the writeback thread

[Shan Hai]

Hi Coly,


On 2018年08月22日 15:29, Coly Li wrote:
> Hi Shan,
>
> On 2018/8/22 3:00 PM, Shan Hai wrote:
>> The writeback thread would exit with a lock held when the cache device is
>> detached via sysfs interface, fix it by releasing the held lock before exiting
>> the thread.
> I will change "the thread" to "the while-loop" when I apply this patch.

That's fine, your change is better.

>> Signed-off-by: Shan Hai <shan.hai@oracle.com>
> Nice catch!
>
> This one should go to stable trees since 4.17 as well. I will CC stable
> maintainers when I submit this one for 4.19.

OK, thanks for the quick response.

Regards
Shan Hai

> Thank you for the fix.
>
> Coly Li
>
>> ---
>>   drivers/md/bcache/writeback.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
>> index 481d4cf..adc583f 100644
>> --- a/drivers/md/bcache/writeback.c
>> +++ b/drivers/md/bcache/writeback.c
>> @@ -679,8 +679,10 @@ static int bch_writeback_thread(void *arg)
>>   			 * data on cache. BCACHE_DEV_DETACHING flag is set in
>>   			 * bch_cached_dev_detach().
>>   			 */
>> -			if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
>> +			if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
>> +				up_write(&dc->writeback_lock);
>>   				break;
>> +			}
>>   		}
>>   
>>   		up_write(&dc->writeback_lock);
>>