Messages in this thread Patch in this message | | | From | Pavel Begunkov <> | Subject | [PATCH v2 1/8] io_uring: leave a comment for drain_next | Date | Sat, 25 Jan 2020 22:53:38 +0300 |
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Draining the middle of a link is tricky, so leave a comment there
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> --- fs/io_uring.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c index e79d6e47dc7b..bc1cab6a256a 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4702,6 +4702,13 @@ static bool io_submit_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe, if (*link) { struct io_kiocb *head = *link; + /* + * Taking sequential execution of a link, draining both sides + * of the link also fullfils IOSQE_IO_DRAIN semantics for all + * requests in the link. So, it drains the head and the + * next after the link request. The last one is done via + * drain_next flag to persist the effect across calls. + */ if (sqe_flags & IOSQE_IO_DRAIN) { head->flags |= REQ_F_IO_DRAIN; ctx->drain_next = 1; -- 2.24.0
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