io_uring: don't pass restart error codes to userspace

-ERESTARTSYS and friends are instructions for the system call exit code,
which either restarts the call or turns them into -EINTR. They are not
supposed to be seen by applications. A request isn't a system call,
nobody looks at what it returns before that is put into a CQE.

The read/write and the networking opcodes convert these codes to -EINTR
by hand. The others don't. An io-wq worker that is blocked in the open of
a FIFO, a tty or some other device, or in a splice from an empty pipe,
and that gets interrupted because the request is cancelled, completes it
with -512:

  IORING_OP_OPENAT, IOSQE_ASYNC       // FIFO without a writer
  IORING_OP_ASYNC_CANCEL              // -EALREADY, worker is signalled
  CQE of the open: res == -512

There are more candidates, like whatever a file system or driver returns
from ->flush(), ->fsync(), ->fallocate() or ->uring_cmd(), or breaking a
lease or delegation.

Take care of it in io_issue_sqe(), which all of them go through. The
helper is moved from rw.c as is. The cost is a compare and a branch that
is not taken per request.

Fixes: 15b71abe7b52 ("io_uring: add support for IORING_OP_OPENAT")
Assisted-by: LLM
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Link: https://patch.msgid.link/20261015-b4-io-uring-fixes-v1-39-c1556f5d7bf5@toxicpanda.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

0 files changed, 0 insertions, 0 deletions