[PATCH 08/12] io_uring: clean up check_overflow flag

Pavel Begunkov
2021-06-14T22:38:10Z

There are no users of ->sq_check_overflow, only ->cq_check_overflow is
used. Combine it and move out of completion related part of struct
io_ring_ctx.

A not so obvious benefit of it is fitting all completion side fields
into a single cacheline. It was taking 2 lines before with 56B padding,
and io_cqring_ev_posted*() were still touching both of them.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
fs/io_uring.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 9c73991465c8..65d51e2d5c15 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -371,7 +371,6 @@ struct io_ring_ctx {
struct io_uring_sqe *sq_sqes;
unsigned cached_sq_head;
unsigned sq_entries;
- unsigned long sq_check_overflow;
struct list_head defer_list;

/*
@@ -408,13 +407,14 @@ struct io_ring_ctx {
struct wait_queue_head sqo_sq_wait;
struct list_head sqd_list;

+ unsigned long check_cq_overflow;
+
struct {
unsigned cached_cq_tail;
unsigned cq_entries;
atomic_t cq_timeouts;
unsigned cq_last_tm_flush;
unsigned cq_extra;
- unsigned long cq_check_overflow;
struct wait_queue_head cq_wait;
struct fasync_struct *cq_fasync;
struct eventfd_ctx *cq_ev_fd;
@@ -1464,8 +1464,7 @@ static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force)

all_flushed = list_empty(&ctx->cq_overflow_list);
if (all_flushed) {
- clear_bit(0, &ctx->sq_check_overflow);
- clear_bit(0, &ctx->cq_check_overflow);
+ clear_bit(0, &ctx->check_cq_overflow);
ctx->rings->sq_flags &= ~IORING_SQ_CQ_OVERFLOW;
}

@@ -1481,7 +1480,7 @@ static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force)
{
bool ret = true;

- if (test_bit(0, &ctx->cq_check_overflow)) {
+ if (test_bit(0, &ctx->check_cq_overflow)) {
/* iopoll syncs against uring_lock, not completion_lock */
if (ctx->flags & IORING_SETUP_IOPOLL)
mutex_lock(&ctx->uring_lock);
@@ -1544,8 +1543,7 @@ static bool io_cqring_event_overflow(struct io_ring_ctx *ctx, u64 user_data,
return false;
}
if (list_empty(&ctx->cq_overflow_list)) {
- set_bit(0, &ctx->sq_check_overflow);
- set_bit(0, &ctx->cq_check_overflow);
+ set_bit(0, &ctx->check_cq_overflow);
ctx->rings->sq_flags |= IORING_SQ_CQ_OVERFLOW;
}
ocqe->cqe.user_data = user_data;
@@ -2391,7 +2389,7 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
* If we do, we can potentially be spinning for commands that
* already triggered a CQE (eg in error).
*/
- if (test_bit(0, &ctx->cq_check_overflow))
+ if (test_bit(0, &ctx->check_cq_overflow))
__io_cqring_overflow_flush(ctx, false);
if (io_cqring_events(ctx))
goto out;
@@ -6965,7 +6963,7 @@ static int io_wake_function(struct wait_queue_entry *curr, unsigned int mode,
* Cannot safely flush overflowed CQEs from here, ensure we wake up
* the task, and the next invocation will do it.
*/
- if (io_should_wake(iowq) || test_bit(0, &iowq->ctx->cq_check_overflow))
+ if (io_should_wake(iowq) || test_bit(0, &iowq->ctx->check_cq_overflow))
return autoremove_wake_function(curr, mode, wake_flags, key);
return -1;
}
@@ -6993,7 +6991,7 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
if (ret || io_should_wake(iowq))
return ret;
/* let the caller flush overflows, retry */
- if (test_bit(0, &ctx->cq_check_overflow))
+ if (test_bit(0, &ctx->check_cq_overflow))
return 1;

*timeout = schedule_timeout(*timeout);
@@ -8702,7 +8700,7 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait)
* Users may get EPOLLIN meanwhile seeing nothing in cqring, this
* pushs them to do the flush.
*/
- if (io_cqring_events(ctx) || test_bit(0, &ctx->cq_check_overflow))
+ if (io_cqring_events(ctx) || test_bit(0, &ctx->check_cq_overflow))
mask |= EPOLLIN | EPOLLRDNORM;

return mask;
--
2.31.1