io_uring: don't forget to adjust io_size

We have invariant in io_read() of how much we're trying to read spilled
into an iter and io_size variable. The last one controls decision making
about whether to do read-retries. However, io_size is modified only
after the first read attempt, so if we happen to go for a third retry in
a single call to io_read(), we will get io_size greater than in the
iterator, so may lead to various side effects up to live-locking.

Modify io_size each time.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index f8492d62b6a15b1fc35883cc746ae65142a2ef47..25fffff27c76c677389832d6d97d0ac66e9e1607 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3548,16 +3548,11 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
                /* some cases will consume bytes even on error returns */
                iov_iter_revert(iter, io_size - iov_iter_count(iter));
                ret = 0;
-       } else if (ret <= 0 || ret == io_size) {
-               /* make sure -ERESTARTSYS -> -EINTR is done */
+       } else if (ret <= 0 || ret == io_size || !force_nonblock ||
+                  (req->file->f_flags & O_NONBLOCK) ||
+                  !(req->flags & REQ_F_ISREG)) {
+               /* read all, failed, already did sync or don't want to retry */
                goto done;
-       } else {
-               /* we did blocking attempt. no retry. */
-               if (!force_nonblock || (req->file->f_flags & O_NONBLOCK) ||
-                   !(req->flags & REQ_F_ISREG))
-                       goto done;
-
-               io_size -= ret;
        }
 
        ret2 = io_setup_async_rw(req, iovec, inline_vecs, iter, true);
@@ -3570,6 +3565,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock,
        /* now use our persistent iterator, if we aren't already */
        iter = &rw->iter;
 retry:
+       io_size -= ret;
        rw->bytes_done += ret;
        /* if we can retry, do so with the callbacks armed */
        if (!io_rw_should_retry(req)) {