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io_uring: clear req->result always before issuing a read/write request 

req->result is cleared when io_issue_sqe() calls io_read/write_pre()
routines.  Those routines however are not called when the sqe
argument is NULL, which is the case when io_issue_sqe() is called from
io_wq_submit_work().  io_issue_sqe() may then examine a stale result if
a polled request had previously failed with -EAGAIN:

        if (ctx->flags & IORING_SETUP_IOPOLL) {
                if (req->result == -EAGAIN)
                        return -EAGAIN;

                io_iopoll_req_issued(req);
        }

and in turn cause a subsequently completed request to be re-issued in
io_wq_submit_work().

Signed-off-by: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
alistair/sunxi64-5.5-dsi
Bijan Mottahedeh 2020-01-15 18:37:45 -08:00 committed by Jens Axboe
parent 78912934f4
commit 797f3f535d
1 changed files with 2 additions and 0 deletions
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2
fs/io_uring.c
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@ -1843,6 +1843,7 @@ static int io_read(struct io_kiocb *req, struct io_kiocb **nxt,
if (!force_nonblock)
req->rw.kiocb.ki_flags &= ~IOCB_NOWAIT;
req->result = 0;
io_size = ret;
if (req->flags & REQ_F_LINK)
req->result = io_size;
@ -1930,6 +1931,7 @@ static int io_write(struct io_kiocb *req, struct io_kiocb **nxt,
if (!force_nonblock)
req->rw.kiocb.ki_flags &= ~IOCB_NOWAIT;
req->result = 0;
io_size = ret;
if (req->flags & REQ_F_LINK)
req->result = io_size;