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io_uring: don't wait when under-submitting 

There is no reliable way to submit and wait in a single syscall, as
io_submit_sqes() may under-consume sqes (in case of an early error).
Then it will wait for not-yet-submitted requests, deadlocking the user
in most cases.

Don't wait/poll if can't submit all sqes

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2019-12-18 19:53:45 +03:00 committed by Jens Axboe
parent e781573e2f
commit 7c504e6520
1 changed files with 4 additions and 0 deletions
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4
fs/io_uring.c
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@ -5135,6 +5135,9 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
submitted = io_submit_sqes(ctx, to_submit, f.file, fd,
&cur_mm, false);
mutex_unlock(&ctx->uring_lock);
if (submitted != to_submit)
goto out;
}
if (flags & IORING_ENTER_GETEVENTS) {
unsigned nr_events = 0;
@ -5148,6 +5151,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
}
}
out:
percpu_ref_put(&ctx->refs);
out_fput:
fdput(f);