On 14/01/2021 21:40, Pavel Begunkov wrote:
> On 14/01/2021 15:50, Marcelo Diop-Gonzalez wrote:
>> Right now io_flush_timeouts() checks if the current number of events
>> is equal to ->timeout.target_seq, but this will miss some timeouts if
>> there have been more than 1 event added since the last time they were
>> flushed (possible in io_submit_flush_completions(), for example). Fix
>> it by recording the last sequence at which timeouts were flushed so
>> that the number of events seen can be compared to the number of events
>> needed without overflow.
>
> Looks good, but there is a little change I'll ask you to make (see
> below). In a meanwhile I'll test it, so the patch on the fast track.
Tested, works good for me.
Apart from the small change I described before
Reviewed-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
>
>>
>> Signed-off-by: Marcelo Diop-Gonzalez <marcelo827@xxxxxxxxx>
>> ---
>> fs/io_uring.c | 29 +++++++++++++++++++++++++----
>> 1 file changed, 25 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 372be9caf340..71d8fa0733ad 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -354,6 +354,7 @@ struct io_ring_ctx {
>> unsigned cq_entries;
>> unsigned cq_mask;
>> atomic_t cq_timeouts;
>> + unsigned cq_last_tm_flush;
>> unsigned long cq_check_overflow;
>> struct wait_queue_head cq_wait;
>> struct fasync_struct *cq_fasync;
>> @@ -1639,19 +1640,36 @@ static void __io_queue_deferred(struct io_ring_ctx *ctx)
>>
>> static void io_flush_timeouts(struct io_ring_ctx *ctx)
>> {
>> - while (!list_empty(&ctx->timeout_list)) {
>> + u32 seq = ctx->cached_cq_tail - atomic_read(&ctx->cq_timeouts);
>
> This assignment should go after list_empty() -- because of the atomic part
> my compiler can't reshuffle them itself.
>
>> +
>> + if (list_empty(&ctx->timeout_list))
>> + return;
> [...]
>> static void io_commit_cqring(struct io_ring_ctx *ctx)
>> @@ -5837,6 +5855,9 @@ static int io_timeout(struct io_kiocb *req)
>> tail = ctx->cached_cq_tail - atomic_read(&ctx->cq_timeouts);
>> req->timeout.target_seq = tail + off;
>>
>> + /* Update the last seq here in case io_flush_timeouts() hasn't */
>> + ctx->cq_last_tm_flush = tail;
>
> Have to note that it's ok to do because we don't mix submissions and
> completions, so io_timeout should never fall under same completion_lock
> section as cq commit,
>
> but otherwise some future locked version of io_timeout would be cutting
> off a part of the current flush window (i.e. this [last, cur] thing).
>
--
Pavel Begunkov
