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for-5.4/io_uring-2019-09-27

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Merge tag 'for-5.4/io_uring-2019-09-27' of git://git.kernel.dk/linux-block

Pull more io_uring updates from Jens Axboe:
 "Just two things in here:

   - Improvement to the io_uring CQ ring wakeup for batched IO (me)

   - Fix wrong comparison in poll handling (yangerkun)

  I realize the first one is a little late in the game, but it felt
  pointless to hold it off until the next release. Went through various
  testing and reviews with Pavel and peterz"

* tag 'for-5.4/io_uring-2019-09-27' of git://git.kernel.dk/linux-block:
  io_uring: make CQ ring wakeups be more efficient
  io_uring: compare cached_cq_tail with cq.head in_io_uring_poll
This commit is contained in:
Linus Torvalds 2019-09-27 12:08:24 -07:00
commit 738f531d87
1 changed files with 57 additions and 11 deletions
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68
fs/io_uring.c
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@ -2768,6 +2768,38 @@ out:
return submit;
}
struct io_wait_queue {
struct wait_queue_entry wq;
struct io_ring_ctx *ctx;
unsigned to_wait;
unsigned nr_timeouts;
};
static inline bool io_should_wake(struct io_wait_queue *iowq)
{
struct io_ring_ctx *ctx = iowq->ctx;
/*
* Wake up if we have enough events, or if a timeout occured since we
* started waiting. For timeouts, we always want to return to userspace,
* regardless of event count.
*/
return io_cqring_events(ctx->rings) >= iowq->to_wait ||
atomic_read(&ctx->cq_timeouts) != iowq->nr_timeouts;
}
static int io_wake_function(struct wait_queue_entry *curr, unsigned int mode,
int wake_flags, void *key)
{
struct io_wait_queue *iowq = container_of(curr, struct io_wait_queue,
wq);
if (!io_should_wake(iowq))
return -1;
return autoremove_wake_function(curr, mode, wake_flags, key);
}
/*
* Wait until events become available, if we don't already have some. The
* application must reap them itself, as they reside on the shared cq ring.
@ -2775,8 +2807,16 @@ out:
static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
const sigset_t __user *sig, size_t sigsz)
{
struct io_wait_queue iowq = {
.wq = {
.private = current,
.func = io_wake_function,
.entry = LIST_HEAD_INIT(iowq.wq.entry),
},
.ctx = ctx,
.to_wait = min_events,
};
struct io_rings *rings = ctx->rings;
unsigned nr_timeouts;
int ret;
if (io_cqring_events(rings) >= min_events)
@ -2795,15 +2835,21 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
return ret;
}
nr_timeouts = atomic_read(&ctx->cq_timeouts);
/*
* Return if we have enough events, or if a timeout occured since
* we started waiting. For timeouts, we always want to return to
* userspace.
*/
ret = wait_event_interruptible(ctx->wait,
io_cqring_events(rings) >= min_events ||
atomic_read(&ctx->cq_timeouts) != nr_timeouts);
ret = 0;
iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
do {
prepare_to_wait_exclusive(&ctx->wait, &iowq.wq,
TASK_INTERRUPTIBLE);
if (io_should_wake(&iowq))
break;
schedule();
if (signal_pending(current)) {
ret = -ERESTARTSYS;
break;
}
} while (1);
finish_wait(&ctx->wait, &iowq.wq);
restore_saved_sigmask_unless(ret == -ERESTARTSYS);
if (ret == -ERESTARTSYS)
ret = -EINTR;
@ -3455,7 +3501,7 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait)
if (READ_ONCE(ctx->rings->sq.tail) - ctx->cached_sq_head !=
ctx->rings->sq_ring_entries)
mask |= EPOLLOUT | EPOLLWRNORM;
if (READ_ONCE(ctx->rings->sq.head) != ctx->cached_cq_tail)
if (READ_ONCE(ctx->rings->cq.head) != ctx->cached_cq_tail)
mask |= EPOLLIN | EPOLLRDNORM;
return mask;