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Subject[PATCH v5] io_uring: don't wait when under-submitting
Date
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>
---

v5: as the v1, but doesn't return -EAGAIN

fs/io_uring.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index fd85f9d3a8e1..eca025f38614 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5133,6 +5133,9 @@ 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;
@@ -5146,6 +5149,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
}
}

+out:
percpu_ref_put(&ctx->refs);
out_fput:
fdput(f);
--
2.24.0
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