On 2019/8/1 1:48, Liu Bo wrote:
> Hi Jun,
>
> On Wed, Jul 31, 2019 at 08:05:03PM +0800, piaojun wrote:
>> Hi liubo,
>>
>> This change has already committed in rhvgoyal's branch:
>>
>> https://github.com/rhvgoyal/linux/tree/virtio-fs-dev-5.1
>>
>
> Thanks for the link, the patch here does one more thing beyond Vivek's current
> code, i.e. the lock protection around req is also removed as it's not
> necessary.
Agreed, and it could save some CPU time.
Thanks,
Jun
>
> thanks,
> -liubo
>
>> Thanks,
>> Jun
>>
>> On 2019/7/30 13:51, Liu Bo wrote:
>>> Right now within virtio_fs_requests_done_work(), virtqueue is protected by
>>> both fsvq->lock and fpq->lock for processing both virtqueue and
>>> fpq->processing_list, however, it is fine for them to be protected
>>> separately.
>>>
>>> Also since %req has been removed from fpq->processing_list, no one except
>>> request_wait_answer() is looking at this %req and request_wait_answer()
>>> waits only on FINISH flag, it's OK to remove fpq->lock after %req is
>>> dropped from the list.
>>>
>>> Signed-off-by: Liu Bo <[email protected]>
>>> ---
>>> fs/fuse/virtio_fs.c | 13 ++++++-------
>>> 1 file changed, 6 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
>>> index 9b3f2e9..d88bb6c 100644
>>> --- a/fs/fuse/virtio_fs.c
>>> +++ b/fs/fuse/virtio_fs.c
>>> @@ -347,21 +347,22 @@ static void virtio_fs_requests_done_work(struct
>>> work_struct *work)
>>>
>>> /* Collect completed requests off the virtqueue */
>>> spin_lock(&fsvq->lock);
>>> - /* grab fpq->lock as req is on fpq->processing list */
>>> - spin_lock(&fpq->lock);
>>> do {
>>> unsigned len;
>>>
>>> virtqueue_disable_cb(vq);
>>>
>>> while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
>>> + /* grab fpq->lock as req is on fpq->processing list */
>>> + spin_lock(&fpq->lock);
>>> +
>>> /* If !connected, req is freed by fuse_abort_conn. */
>>> - if (fpq->connected) {
>>> + if (fpq->connected)
>>> list_move_tail(&req->list, &reqs);
>>> - }
>>> +
>>> + spin_unlock(&fpq->lock);
>>> }
>>> } while (!virtqueue_enable_cb(vq) && likely(!virtqueue_is_broken(vq)));
>>> - spin_unlock(&fpq->lock);
>>> spin_unlock(&fsvq->lock);
>>>
>>> /* End requests */
>>> @@ -373,10 +374,8 @@ static void virtio_fs_requests_done_work(struct
>>> work_struct *work)
>>>
>>> /* TODO zeroing? */
>>>
>>> - spin_lock(&fpq->lock);
>>> clear_bit(FR_SENT, &req->flags);
>>> list_del_init(&req->list);
>>> - spin_unlock(&fpq->lock);
>>>
>>> fuse_request_end(fc, req);
>>> }
>>>
> .
>
