[Devel] [PATCH 1/2] fs/fuse kio: add FUSE_S_FAIL_IMMEDIATELY check in pcs_fuse_submit()

[Pavel Butsykin]

On 01.02.2019 17:24, Kirill Tkhai wrote:
> On 24.01.2019 16:12, Pavel Butsykin wrote:
>> Fuse file with FUSE_S_FAIL_IMMEDIATELY state should not allow to execute new
>> requests. But in case of kio requests it doesn't work because the status check
>> is located behind kio.op->req_send(). To fix this let's add the status check
>> in pcs_fuse_submit().
>>
>> Signed-off-by: Pavel Butsykin <pbutsykin at virtuozzo.com>
>> ---
>> Note:
>> applies on top of "[PATCH v2] fs/fuse kio: invalidate files for kio"
>>
>>   fs/fuse/kio/pcs/pcs_fuse_kdirect.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/fs/fuse/kio/pcs/pcs_fuse_kdirect.c b/fs/fuse/kio/pcs/pcs_fuse_kdirect.c
>> index da4b5fba03fb..3ca1ce2d6bd5 100644
>> --- a/fs/fuse/kio/pcs/pcs_fuse_kdirect.c
>> +++ b/fs/fuse/kio/pcs/pcs_fuse_kdirect.c
>> @@ -986,6 +986,11 @@ error:
>>   
>>   submit:
>>   	spin_lock(&di->kq_lock);
>> +	if (req->ff && test_bit(FUSE_S_FAIL_IMMEDIATELY, &req->ff->ff_state)) {
> 
> FUSE_S_FAIL_IMMEDIATELY is set under fc->lock, while it's checked under kq_lock.

Actually this lock is needed to protect listing fi->rw_files, not for
set_bit.

> How do you guarantee visibility?

It's atomic operation, so I should just guarantee
synchronization with fuse_invalidate_files() which is carried out by
set_bit(FUSE_S_FAIL_IMMEDIATELY, ) + kpcs_kill_requests() and the locked
check.

> 
>> +		spin_unlock(&di->kq_lock);
>> +		req->out.h.error = -EIO;
>> +		goto error;
>> +	}
>>   	list_add_tail(&req->list, &di->kq);
>>   	spin_unlock(&di->kq_lock);
>>   
>>