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io_uring: don't keep looping for more events if we can't flush overflow

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It doesn't make sense to wait for more events to come in, if we can't
even flush the overflow we already have to the ring. Return -EBUSY for
that condition, just like we do for attempts to submit with overflow
pending.

Cc: stable@vger.kernel.org # 5.11
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-03-04 17:15:48 -07:00
parent 46fe18b16c
commit ca0a26511c
1 changed files with 12 additions and 3 deletions
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15
fs/io_uring.c
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@ -1451,18 +1451,22 @@ static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force,
return all_flushed;
}
static void io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force,
static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force,
struct task_struct *tsk,
struct files_struct *files)
{
bool ret = true;
if (test_bit(0, &ctx->cq_check_overflow)) {
/* iopoll syncs against uring_lock, not completion_lock */
if (ctx->flags & IORING_SETUP_IOPOLL)
mutex_lock(&ctx->uring_lock);
__io_cqring_overflow_flush(ctx, force, tsk, files);
ret = __io_cqring_overflow_flush(ctx, force, tsk, files);
if (ctx->flags & IORING_SETUP_IOPOLL)
mutex_unlock(&ctx->uring_lock);
}
return ret;
}
static void __io_cqring_fill_event(struct io_kiocb *req, long res, long cflags)
@ -6883,11 +6887,16 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
iowq.nr_timeouts = atomic_read(&ctx->cq_timeouts);
trace_io_uring_cqring_wait(ctx, min_events);
do {
io_cqring_overflow_flush(ctx, false, NULL, NULL);
/* if we can't even flush overflow, don't wait for more */
if (!io_cqring_overflow_flush(ctx, false, NULL, NULL)) {
ret = -EBUSY;
break;
}
prepare_to_wait_exclusive(&ctx->wait, &iowq.wq,
TASK_INTERRUPTIBLE);
ret = io_cqring_wait_schedule(ctx, &iowq, &timeout);
finish_wait(&ctx->wait, &iowq.wq);
cond_resched();
} while (ret > 0);
restore_saved_sigmask_unless(ret == -EINTR);