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    Subject[PATCH 5.6 117/254] io_uring: fix ctx refcounting in io_submit_sqes()
    Date
    From: Pavel Begunkov <asml.silence@gmail.com>

    commit 48bdd849e967f1c573d2b2bc24308e24a83f39c2 upstream.

    If io_get_req() fails, it drops a ref. Then, awhile keeping @submitted
    unmodified, io_submit_sqes() breaks the loop and puts @nr - @submitted
    refs. For each submitted req a ref is dropped in io_put_req() and
    friends. So, for @nr taken refs there will be
    (@nr - @submitted + @submitted + 1) dropped.

    Remove ctx refcounting from io_get_req(), that at the same time makes
    it clearer.

    Fixes: 2b85edfc0c90 ("io_uring: batch getting pcpu references")
    Cc: stable@vger.kernel.org # v5.6
    Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/io_uring.c | 1 -
    1 file changed, 1 deletion(-)

    --- a/fs/io_uring.c
    +++ b/fs/io_uring.c
    @@ -1242,7 +1242,6 @@ fallback:
    req = io_get_fallback_req(ctx);
    if (req)
    goto got_it;
    - percpu_ref_put(&ctx->refs);
    return NULL;
    }


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